Jump to content


Garage Vehicles

Disney Pics 003.jpg

Jeep Wrangler (1992)

Owner: Megatron

Added: 27 September 2013 - 08:56 AM

20131023_113518.jpg

Dodge Ram 3500 (2006)

Owner: Megatron

Added: 25 September 2013 - 07:37 AM

6-inch XJ suspension lift (Lead).jpg

Jeep XJ Cherokee 4WD Sport 4-door (1999)

Owner: Moses Ludel

Added: 15 September 2013 - 01:16 PM


Photo
- - - - -

Rebuilding the Honda XR650R Motorcycle Upper Engine

dirt motorcycle dirt motorcycle forum off-road motorcycle dual-sport motorcycle dirt bike discussion dirt bike how-to dirt motorcycle how-to Honda XR

  • Please log in to reply
25 replies to this topic

#1 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 28 December 2013 - 04:54 PM

The magazine's Honda XR650R performs remote field work as an HD video filming platform.  Reliability is essential.  After purchasing the bike in non-running condition, I ran a compression test when the engine refused to start.  I moved from the simple compression test to a full-fledged cylinder leak down test, the pinpoint diagnostic tool of choice.  Want to know more about a leak down test? Click here for the 4WD Mechanix HD Video Network feature and details on the leak down test!

 

High cylinder leakage called for a top end inspection and repairs.  That tear down for inspection can be found at the magazine as the HD video how-tohttp://www.4wdmechanix.com/Honda-XR650R-Motorcycle-Upper-Engine-Rebuild-Part-1-Tear-Down-How-to.html.

 

Attached File  Cylinder Leak Down Test-8.JPG   96.97KB   0 downloads Attached File  Honda XR650R Engine Teardown-8.JPG   92.29KB   0 downloads

At left is the cylinder leak down test covered in the HD video how-to. At right is the actual top engine tear down, part of the current rebuild. See both HD videos at the magazine for details! 

 

The step-by-step teardown, rebuild and assembly are now a single HD video streaming rental at Vimeo On Demand.  Included in this rental is a bonus feature on valve adjustment (which is also available as a separate streaming rental). You will find this 54-minute feature at: http://www.vimeo.com...and/hondaxr650r.

 

Here is a review of that rental video:

 

     "Coming across this video couldn't have been more fortuitous - both in timing and content. I happened to inherit a motorcycle of the exact same type and with the exact same problems as the one starring in the clip. The author/producer treats the subject thoroughly and with close-ups giving great detail of the matter at hand. Not only that, he has an online magazine with a forum through which he is eminently available for input and feedback. Having watched this gave me the confidence to embark on the solution on my own - saving loads of money and learning in the process."—David E.



#2 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 02 July 2014 - 06:34 PM

Question for you, Moses:

 

Is there a difference between the compression stroke and the exhaust stroke on the XR when the cam is out? I’m worried that if I’m 360 degrees off on reassembly, I’ll put it back together with the ignition firing on the wrong stroke. Or does the ignition simply fire every time the crank goes around so that it doesn't matter? 

 

D.



#3 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 29 July 2014 - 07:17 AM

David, for the Honda XR650R, the ignition fires on each TDC of the piston, two times during the four strokes.  Specifically, the ignition fires at the top of the compression stroke and top of the exhaust stroke.  The exhaust stroke firing keeps the spark plug cleaner and otherwise will not affect performance. 

 

Simply put, for valve timing, as long as the piston is at top-dead-center (TDC) on the Honda XR650R, you can align the camshaft sprocket properly.  Your only concern is to have the camshaft and its sprocket tensioned on the pull side.  To accomplish this, always bring the piston to TDC without going too far and needing to back up.  This way, there is pull tension on the camshaft sprocket and no chain slack.  This prevents a valve timing error due to chain slack.

 

Following the camshaft and sprocket installation, I always recheck the valve timing after installing the chain tensioner.  After installing the tensioner, rotate the crankshaft in its normal direction of rotation, orienting the cam sprocket marks properly.  Bring the piston slowly to TDC and stop there.  Tension applied at the backside of the chain, the cam sprocket timing marks should be exactly where you want them with the engine running.

 

Moses



#4 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 09 August 2014 - 07:32 AM

Thanks for confirming! That's what I thought.

 

But then if I was wrong, I would feel pretty stupid once everything was together but wouldn't run!

 

D



#5 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 10 August 2014 - 11:33 PM

Very sensible to be clear here.  As you note, valve timing is a big thing with a four-stroke, especially an engine with an overhead camshaft, long chain, a tensioner and a timing sprocket that must align properly.  Glad you confirmed!

 

Looking forward to your success story with this engine.  You'll really like the renewed performance, David!

 

Moses



#6 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 11 September 2014 - 12:48 AM

Hi Moses,

 

I reassembled the cylinder, piston and head last night - taking little "computer breaks" along the way to confirm what I was doing by looking at your video of the rebuild. What a great resource to have in this backwoods! (I mean the internet - but your video as well!)  :D

 

I still have work to do (valve adjustment among other tasks), but I'll give a few insights from my experience so far:

 

  1. For people sticking with the original cam: When reinstalling the retainer clip for the auto-decompress plunger, note that the clip can seem like it's properly installed, but in fact, it's possible that it is riding in the space below the groove provided. If so, this will prevent the plunger from rising to its intended height. It pays to double check with a good flashlight and your reading glasses. 
  2. When reinstalling the camshaft (I suppose this applies no matter what version of cam you use), you should insert the 8x17.5 cam-end retainer dowel in the head before dropping the cam in. Once the cam is in and the sprocket on, the dowel can no longer be inserted (actually, it probably can, but it would involve some force that I hesitated to apply). As you can gather, I had to remove the freshly torqued cam sprocket bolts, slide the sprocket off the shoulder on the cam, move the cam, insert the dowel, put the cam back in place with the sprocket, re-time the sprocket (I marked it so at least it was easy), reinstall and retorque the sprocket bolts, risk dropping stuff in the engine because now you lost patience, bla bla.. You get the picture.
  3. I suspect that the long 6 mm bolts that go in the right side of the valve cover down into the cylinder are prone to stretching - I've not torqued one of them to full spec.as it feels a little "iffy."

Overall, things have gone smooth as butter - in large part thanks to the video. Not only is it "directions" on how to do things, but it's also a photographic record. I found myself going back, not always to listen to you, but to find an angle showing where that little doohickey lying on the floor is supposed to go!  

 

I'm surprised by how much resistance there is to turning the engine now, but I don't suspect there's anything wrong. It's just that it seems there's way more compression now than before - yet I haven't even installed the spark plug!!!

 

Now off to try to find some motor oil! That's another thing that we suffer here - no fancy selection of oils. 

 

D.



#7 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 11 September 2014 - 12:36 PM

Pfffttt... Seems I have something strange going on with the autodecompressor despite my efforts to ensure that the moving parts were rotating the right way. I even removed the magneto cover to ensure counter-clockwise rotation and proper TDC-C (had not done this before as I felt comfortable with just looking at the mark through the peep hole).

 

Despite all of this, the right side exhaust valve is asking for a huge amount of backing off the adjuster screw. I tried to include a photo, but the computer is not cooperating. And then when I turn the engine over, I notice that the right side valve has a distinct timing delay over the left for opening and a similar amount of timing advance for closing (though I think I understand the exhaust valves are supposed to open in concert).

 

Time to do some more sleuthing. Unfortunately, the fridge is dry, so there's no more fuel to keep me going (I mean beer - and jetting is not critical in this matter), so the investigation will have to wait....



#8 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 11 September 2014 - 12:48 PM

On the plus side, I have found a place to get "good" oil. It's a South African outfit called Engen; and they sell synthetic 10W40 full-synth in half liter bottles for about $5 a pop. I hope it mixes well with the 1/10th liter of Lucas break-in oil that was mentioned as "de rigueur" by Moses. 

 

I suspect that the "with zinc" additive is more "break-in important" for cams (of which mine is not new - though it was for Moses) than for rings and pistons (which have indeed been changed in my case). In any event, this lube will only stay in there for the first few hundred kilometers of break-in before getting swapped out with 100% full-synth. I hope there's a market for the Lucas stuff among my buddies since I brought back 2 pints/liters and I only need about 1/10th of that for the XR!

 

Whatever the case, having "good" lube of any kind will surely work wonders for this motor that has apparently been starved of TLC in its previous life.

 

More later!

D.



#9 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 11 September 2014 - 05:55 PM

You're making very good progress, David!  Yes, the camshaft bearing set pin should be in place before installing the camshaft and sprocket.  This is shown in the video, but I'll add a footnote.  Will also emphasize the importance of seating the oil plunger circlip in its groove.  If the valve clearance and valve timing are correct, the resistance that you're feeling without the spark plug in place should be the tension from the valve springs.

 

Exhaust valve unseating is part of the auto-decompression system.  When adjusting the valves, you must bring the rockers and valves into position without passing TDC on the compression stroke.  If you do pass TDC, continue rotating the crankshaft two more turns to bring the piston once again to TDC on the compression stroke.  If you do go too far, the auto-decompressor will unseat the exhaust valve to relieve compression.  This is what you're experiencing, making you want to loosen the adjuster.  The gap closure and valve opening is actually the auto-decompressor working. 

 

Try just bringing the piston to TDC on the compression stroke while rotating the crankshaft in its normal direction of rotation.  Review the valve adjustment section of the video.  See 25:41-minutes.  You'll recall that the intake rocker arms open together, but the exhaust valve rockers are separated.  One exhaust valve rocker works with the auto-decompressor on the camshaft.  The other exhaust rocker works with the hand lever decompressor.

 

Note: As a precaution, check or adjust the hand lever decompressor free-play to make sure there is no interference when adjusting valves.

 

As for your break-in oil, the zinc additive will help.  Do not use the synthetic oil yet.  You want enough friction at the piston rings to seat the rings.  Your synthetic oil offers exceptional lubricity, which can prevent normal ring seating.  At your first oil change, you will remove the non-synthetic oil and zinc additive.  Now you can refill with your synthetic oil if the rings are seated.  I would go to 400 kilometers before this first oil change.  That way, the rings will surely be seated.  As a footnote, I installed a new oil filter after the first 50 miles and topped off the oil.  This gets rid of initial flushing and wear-in particles that may accumulate in the oil filter. 

 

Check the oil level immediately after shut-off, before the oil drains downward into the sump and engine.  Run the engine, idle down, shut off and immediately check the oil level.  If you wait, a false reading will lead to overfilling and possible damage to seals and crankcase sealing. 

 

Moses



#10 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 13 September 2014 - 02:46 AM

Sure enough, it was just too late at night for me to have the patience in getting the cam off the autodecompressor. Yesterday with a little more time on my hands, I rotated the crank a few more times (it actually took a whack at the kickstarter), and the decompressor clicked off, letting the right side exhaust valve lash go wide as expected. I've reset it now, and it would seem that all is good to go.

 

Carb, vacuum and breather hoses, and new cables are the next step of reassembly.

 

D.



#11 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 13 September 2014 - 12:50 PM

David...In the video, you can see me lubing the camshaft bearings and sprocket/chain with LubeGuard.  The auto-decompressor mechanism could gain from a light lube in that process.  This is a busy mechanism with a one-way, spring loaded clutch.  It can get sticky.

 

On my XR650R, pre-rebuild, the motorcycle had set for a long period in storage (previous owner).  I attempted to kick over the engine and had the auto-decompressor jam several times with increased kicking effort and even a lock up of the kick starter, which did free itself without damaging parts, fortunately.  This was another incentive for my opting out of the auto-decompressor and installing the Hot Cams Stage 1 camshaft to eliminate the stock auto-decompressor. 

 

Again, there is nothing intrinsically wrong with the auto-decompressor or stock camshaft, many racers liked the feature.  In "Dust to Glory", it appears that the engines use an auto-decompressor with Stage 2 level camshafts, as the riders are kicking repeatedly and in rapid succession during restarts at the pits.  This is not possible with the manual decompressor, as it takes a few seconds to "find" TDC and tip over slightly before kicking the starter through.  Though this may sound time consuming, I can start a high compression thumper with just the hand lever decompressor in about the same time or less than an auto-decompressor. 

 

For high compression XR thumpers, Honda capitulated early on and added the auto-decompressor for kick starting.  My XR350R and XR500R each have cable actuated decompressor mechanisms.  The kick starter mechanism actuates an exhaust valve unseating lever via an external cable to the rocker box.  The auto de-compressor became incorporated with the camshaft on the XR600R, a feature that the XR650R inherited.

 

Note: Some members are having difficulty adding photos or illustrations to posts.  Simply click on "More Reply Options" next to the "Post" button.  Drop to the bottom of the full editor box, and you'll find the "Attach Files" button at the left.  That will open up your computer file browser, where you can pick the photo file or any other file (several at one time if you like), then add it/them to the attachments.  You'll see the photo(s) or file load.  Now place the curser at the point in the edit box where you want the photo to appear.  Click on the "Add" button next to the loaded file.  The bracketed file description will appear in the edit box.  When you "Post", the photo (thumb) or file (like the PDFs I like to toss out for folks) will appear in position at your post!

 

Moses



#12 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 17 September 2014 - 02:12 PM

Ok. It's done.   ...nearly. What's important is; the engine has been started. Hurray!

 

It surprised me a little that it started on the 1st kick after having been turned over a few times with no spark just to get some oil circulating. The idle immediately settled to a steady lope (no idea of exact RPM, but it's reasonable), and throttle blips gave instant reaction.

 

What remains is to do the break-in, flush the cooling system, get the master link (non clip-type) of the new chain peened (if anyone has ideas of how to do this without tools, please chip in!), and then eventually readjust the valves and retorque the cylinder head. 

 

Retorque the head? Yes, I guess it'll have to be done, as I notice to my chagrin, some web sources are maybe not as reliable as others. I looked up the torque spec to be 44 N-m or something like that (and Moses, I think that's what your video says?). After having gotten my hands on a factory manual, I see the torque is supposed to be somewhere between 60 and 70 N-m...  but by then, it was too late to do anything about it. Oh well.

 

Anyway, the first ride should be interesting. The GCR lives! (by the way I just invented it - GCR = Grand Cochon Rouge)

 

D.

 

 

Attached Files



#13 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 17 September 2014 - 05:13 PM

David, if you used an MLS head gasket, there would normally be no need for re-torque.  In the video, I devote three full minutes to cylinder head nut torque details.  Review the video from 14:00 minutes to 17:00 minutes.  Actual final torque, established by tightening the four cylinder head nuts uniformly and in cross, is 49 ft-lb.  Yes, it's 49 foot-pounds or approximately 67 Nm.   

 

Make a point of re-adjusting that head torque real soon to prevent coolant seepage into the cylinder or damage to the head gasket that would require removal of the head for gasket replacement.  I'm very pleased and excited that you have the engine running, you're very close to a finished job at this point!  If the head gasket is the tough MLS type, you likely are fine here if you re-torque the head now.  (Regardless of the current torque setting, if uniform and equal, the gasket is flat and probably sealing.)  This will require removal of the rocker box and, as you suggest, a fresh valve clearance check and adjustment.  All of this will go quickly, you're familiar with the process!

 

Keep us posted...and congratulations, David!

 

Moses



#14 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 18 September 2014 - 02:27 PM

So... the BRP (aka GCR) fired up so nicely, idled steadily and sounded so crisp on the first day, I was really excited to take it for a spin. In the end, it was just a warning for me not to be so smug and regale in my mechanical skills. Here's the deal:

 

I wanted to start the break-in process today, but pulling out of the driveway (for the "first ride"), the bike stalled already once. And over the next 5 kms, it stalled again a number of times. It got so bad that I figured I should go home - by which point I couldn't even start it with the kick anymore. I had to rely on gravity - rolling starts. It seems to accept running at what I imagine to be about 3,000 RPM, but anything below that, it stalls.

 

I wound in the idle stop screw to force it to run while I played with the fuel screw, but the adjustments seemed to make no difference. Eventually, I took off the carb and disassembled and cleaned everything again - and though I did find some suspect areas, the effort produced no result. Tomorrow I will have access to a friend's compressor to blow some air through the thing, but I'm not convinced it will have any impact.

 

It's as if the engine is running out of gas. Such a contrast from yesterday  :(.

 

I've run through all the obvious culprits and have found things that might have had an impact, but the result is nix. Before the carb removal tomorrow, I'll do a test of the fuel supply (to the bowl) by hooking up a clear plastic hose to the drain to see if the level is a problem. If that's not an indicator, then the carb has got to come off again. I wasn't looking forward to that....

 

D.



#15 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 18 September 2014 - 05:20 PM

David, fuel hose disconnected to the carburetor, hold a clean can underneath the hose end, and turn on the petcock.  Does sound like fuel starvation, and this can be the filter in the tank/petcock assembly.  If slow or minimal fuel flow, drain the tank fuel and remove the fuel petcock carefully from the tank.  See if there is an obstruction or clogged filter.

 

You do need a fuel filter, especially at Burundi.  On my BRP, the petcock had disintegrated from setting with ethanol fuel in the tank during storage by the previous owner.  The plastic filter was splintered and clogged, and I bought a complete (new) petcock with filter and gasoline-resistant O-ring (a must!).  If you want to wait on the petcock and factory filter, temporarily eliminate the petcock filter in the tank, get a sufficient flow universal fuel filter for inline use between the tank petcock and carburetor.  This is gravity flow and easy to accommodate.  Make it safe and both leak and melt proof.  I prefer Euro style hose clamps, the screw and nut band type.

 

Your 650 engine ran too well and started perfectly.  There is every reason to suspect a fuel supply problem as a starting point for troubleshooting...We'll get you out on the road again!  You've gotta experience this beast in top form...

 

The photo of your XR650R motorcycle with future rider nearby is very cool!  No visit goes by without my Grandson Camden sitting on Grandpa's "Big Red Big"—three of his earliest words.  Boys and their mechanical toys!

 

Moses



#16 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 19 September 2014 - 12:41 AM

Hi Moses,

 

Thanks for the feedback. I had already pulled the petcock, cleaned the filter screen (which, aside from being dirty, is in a pitiful state - goes on the list of more parts to order), checked the filler cap vent and hose, checked the petcock for flow, etc. Even though the screen is bad, fuel flows fine through the petcock. I did not disassemble the petcock. Anyway, if the bike runs at 3000 revs and upwards, you'd think that fuel delivery to the bowl is not the problem. 

 

I've run a coat hanger through all of the carb vent tubes (one was blocked), adjusted the float level (it was way off), pulled and re-pulled the slow speed jet, fuel screw, and sprayed carb cleaner all over the garage.

 

I have a suspicion about the fuel screw though. Since the old one was apparently screwed into the stop hard enough to mangle the head (which, as you will remember, required an easy-out to remove), there may be some damage in the seat - but I can't see anything obvious. I'm just thinking back to when I got the bike... It actually ran no problem with the screw seemingly turned all the way in to the stop. This might mean there's something wrong with the seat?? The installation order of the fuel screw is O-ring, washer, spring and then screw, right? 

 

The only things I have not done (that I can think of) are to pop out the needle jet (though I did have the needle out previously), and take the air-stop diaphragm thingy apart.

 

I'll do the visual check trick with the clear hose to be sure that the bowl is not running dry. If nothing to report there, I'll take it all apart again and have at it with my friend's air compressor. While it's apart, I'll probably take a look at exhaust valve clearances again - just to eliminate the autodecompressor from the list of suspects...  Another thought is to remove the muffler to see if it'll run any different with it off. That will eliminate the possibility that a mouse or rat made a home in there in the middle of the welding job :)

 

Another thing to do would be to replace the fuel. It's not likely, but it could have gone bad in the few months the bike has been apart. But if it did, then how to explain that the bike ran so well on the first start-up? Can fuel go bad overnight?

 

Phooey. I wanted to be riding and not wrenching now.

 

D.



#17 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 19 September 2014 - 06:36 AM

I like your planned "checks", each makes sense, David...

 

Backing this up just a bit, let's rule out any engine assembly related stuff.  You were attuned to the video during cylinder and head engine assembly.  As I noted in the earlier reply, I walk the viewer carefully through the cylinder head nut tightening sequence and repeatedly use the reference "49 ft-lbs" final torque, even citing four recommended ft-lbs torque steps as you bring these nuts up to full torque, then a recommended recheck twice at the 49 ft-lbs.  (All of this is between minutes 14 and 17 in the rental video.)  If you followed these focused steps, the torque should be right, and you're past any concerns about the engine compression seal and air-fuel mixture dilution from a seeping head gasket.  On that same note, the valve timing chain tensioner was presumably in good condition and should have tensioned the chain properly after installation.  This would assure proper valve timing and chain tension.

 

If the engine is sealing properly, you're on the right track at the carburetor.  If fuel volume to the carburetor is adequate, there are two concerns here.  You reset the float, and that's a big one, as the float level must be high enough to keep fuel flowing sufficiently and not so high that there is flooding or spilling of fuel out the overflow vent tubes.  Set properly, the float level will not seep fuel with the carburetor leaning moderately, like when the bike is on its kickstand.

 

So let's move to the carburetor idle pilot screw adjustment.  Yes, you have the installation sequence correct:  O-ring, washer, spring then screw.  To clarify, this pilot screw is a fuel supply screw, meaning that as you screw it out or open it, more fuel flows into the air stream of the carburetor.  If the engine ran with this pilot jet screwed in all the way, it's obviously getting fuel from somewhere.  Before looking for an internal fuel leak (high float level, seepage past a passageway or casting, etc.), make sure the choke is opening completely.  Find a stable idle point with the cable connected idle stop screw, even if the speed is somewhat fast.  Now turn the pilot jet screw inward and out to see if that has any effect on idle speed.

 

If the engine won't idle down with the idle speed screw setting, usually it's not getting enough fuel.  If it races and won't slow, its getting too much fuel/air combined.  Extra air can be an air leak between the manifold and head or manifold and carburetor, and this would raise idle speed.  Engine running (as slow as it is capable), take your WD40 and carefully spray around the intake (rubber) manifold with the engine speed as stable as possible.  (Avoid spraying hot surfaces like the exhaust system, you don't want to set yourself, the bike or the garage on fire!  A fine mist is all you should need, vacuum will pull the WD40 into the intake stream and change the engine speed.)  If you hear a change in engine speed, there is a manifold or attachment point leak.  Correct this. 

 

Note: To rule out cylinder head gasket seepage, with the engine running, spray a fine mist at the head gasket mating point around the cylinder barrel and head.  Again, avoid the exhaust heat and risk of igniting the WD40.

 

Other sources of air leaks can be the carburetor slide cover or the cut-off valve cover and port seal.  Check these areas with WD40 mist, too.  If there is an air leak, little fuel from the pilot jet may be enough to increase engine speed and give a "false" idle setting.  Eliminate any and all external air leaks, beginning at the air box to carburetor inlet (to protect the engine from dust seepage) to the cylinder head.

 

Also, I would check for a throttle shaft leak, another point where air can enter from the outside.  Visualize idle mixture as dependent on air only coming from the correct sources within the carburetor.  Rule out slide to bore wear, which can also throw off the air flow—here, too much air seeps between the carburetor slide bore and the slide.  Slide and bore wear was a notorious leak point on vintage British Amal carburetors, the Concentric type in particular.  The engine would warm up, and the idle speed would creep up.  There was a ready source of air and a fuel supply. 

 

The slow jet and main jet should not be involved in the base idle speed and mixture issue.  (You're using the OEM Euro slow jet, a 65, right?  I'm running a higher flow 68 at 4400 feet elevation with no issues around adjusting the idle mixture.)  Needle height should not be an issue, Euro OE clip position is 3rd groove from top, same place I'm using.  Make sure the needle clip seats properly at the top of the slide.  Be sure the needle seat is in proper position...If the engine idles at normal operating speed warm (around 1400 rpm) with the pilot screw turned in all the way, the carburetor is supplying fuel from somewhere.  If the engine won't idle down to 1400-1500 rpm, it needs either air or fuel, or both—there's either an air restriction or a fuel restriction.

 

David, here are some helpful PDFs, a carburetor schematic and the factory steps for setting the pilot jet screw.  Zoom-in for details on the schematic.  Account for all of the parts within the carburetor:

 

Attached File  Honda XR650R Keihin Carburetor Schematic.pdf.bmp   6.35MB   1 downloads Attached File  Honda XR650R Keihin Pilot Jet Adjustment.pdf   230.03KB   1 downloads

 

Moses



#18 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 20 September 2014 - 09:34 AM

Hi Moses,

 

I've not done the retorque yet. I'm trying some easier steps first.

 

The initial step was to replace the fuel. That made it better but it could just be my imagination. Here's the video after I did that: http://youtu.be/OzyQ5Z0Qo9w What you might not notice from the video is that I forced the bike to run by turning up the idle stop screw. I'm kicking the bike with about 1/3 throttle from the grip. At this stage, kicking with no grip throttle will not start it (warm/hot).

 

At one point while fiddling with the mixture screw, I overheated (I figured that might happen :(), so I got a fan in front of the motor. Playing with the mixture screw had no noticeable impact on how the bike ran. Hard to tell though since it wasn't running good anyway.

 

I also checked the float level/bowl fuel supply with a plastic hose. Attached is a photo - with the engine running.  It might look a little low in the photo, but that's just because the bike is on the side stand. Whatever the case, the fuel supply was constant, so that's not the problem either. 

 

Now with the carb apart, I find not much to be suspicious of. I have yet to take the slide out again, but I can already tell from the last disassembly that the slide looks worn. Looks may not be the last word through since it moves up and down in the bore extremely nicely.

 

But your mention of the throttle shaft gives me a new train of thought: Since I cleaned so much crud off the top of the carb - including the shaft assembly, I think that I may have opened up a source of outside air. In the carb body where the shaft goes in there is a felt ring of some kind (at least I think it's felt) that fits in a groove (just to the outside of the plastic washer) and surrounds the shaft. I suppose its purpose is to keep foreign bodies (and air) from getting into the carb via the throttle shaft. In aggressively cleaning, I may have damaged the felt. Furthermore, the Moose kit did not give a new o-ring to seal the top cover of the carb. My feeling is that if the top cover seal and the shaft seal are good, a worn bore wouldn't make much difference as there's no air supply above the slide to seep in. But in my case, with a worn slide-to-bore fit, bad shaft seal, and bad top cover seal, this may just be a logical avenue to attack.

 

The question still remains though - why did the bike run good on the first day? A suspicion is that because I had sprayed the slide with WD-40 before putting it back together (ran out of carb cleaner), and I had greased the shaft, that helped seal things temporarily. Once the WD and the grease were progressively sucked away, air started to bleed through. Plausible? 

 

But I don't see this felt on the carb parts fiche! And even if I had a new one, to get it in without damage might be a challenge. Any thoughts as to how to seal this? I'm thinking (as a test at least) that I'll just schmatta it with silicone sealer (from the outside) in the hopes that it'll fill the gap without sending junk into the carb. Ditto for the carb top o-ring (though I might try to make a new o-ring from an extra valve cover o-ring I have - like I did for the thermostat housing). Maybe I could even make an o-ring for the shaft, but it wouldn't be good if it interfered with throttle action...

 

So... back to the basement.

Attached Files



#19 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 20 September 2014 - 02:28 PM

Hey Moses,

 

Did you ever notice that the parts fiche shows the mixture screw assembly order in reverse? Take a look...

 

Any merit to that?

Attached Files



#20 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 21 September 2014 - 01:18 PM

David...Part #1 does look like the O-ring.  This is illogical and not the same depiction as the Honda shop manual schematic.  We would not put the O-ring outboard of the washer.  The pilot screw shoulder would chew up the ring.  By design, the washer should compress or "sandwich" the O-ring against the seat in the carburetor's pilot screw bore.   

 

The washer does go outboard of the O-ring and rides against the screw shoulder.  This is the only way to get an effective seal and preserve the O-ring. 

 

As a footnote, the screw should be turned in gently, as the O-ring is vulnerable.  Seat the screw very lightly...I take care to make sure the thin nose stem of the pilot screw is engaging the tiny hole in the pilot bore of the carburetor body.  If installed properly, the screw will be recessed into the body when seated.  If it sticks out beyond the body, the screw is not aligned properly.  As we know, a misaligned stem will bend under too much pressure.

 

Use care to make sure the stem of the pilot screw is centered on the tiny pilot hole...

 

Moses



#21 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted 21 September 2014 - 01:58 PM

So, a good part of my Sunday was spent in the basement in company of my BRP's carburetor. I went through it with a fine tooth comb (and - not joking - a magnifying glass), and I took a few close-ups of potentially suspect parts. In the end, however, I may have just been out-thinking myself.

 

Before putting the carb back on, I pulled the spark plug to see what it looked like and was a bit surprised to see it all black and sooty. I hadn't expected that since I had assumed my problem was fuel starvation. By then I was all confused. 

 

So I started to check valve clearances again - not that I figured I'd find anything out of the ordinary having set them just a few days before. Well, dammit if both intakes as well as the left side exhaust were so tight I couldn't even get a shim under them! Is it possible that I set them using a TDC from a parallel universe? 

 

Thinking back to the initial valve adjustment, I had done those three and then run into a problem with the right side exhaust (because of the autodecompressor). That right exhaust valve was done the next day with a fresher mind (and apparently a real TDC as it appears to be the only one set correctly).

 

Anyway, I readjusted the 3 out of spec, and buttoned everything up. It started easily and ran just perfectly from the get-go with a normal idle. I could almost hear the inventors of the autodecompressor laughing at me from Hamamatsu. All this theorizing... and it turns out (most likely) that the problem was of my own making.  :angry:  :angry:

 

I won't start jumping up and down yet however. I will ride it up & down the hill tomorrow to see if indeed all is sorted.

 

The (hopefully) definitive answer will come once I ride it.

 

D.



#22 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted 21 September 2014 - 02:05 PM

This is a relief, David, and it makes sense.  Good that you were unable to operate the cycle much in this state...At least you know the carburetor is spot on now!

 

Looking forward to an update with your riding report, should reflect a smile on your face!

 

Moses



#23 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted Yesterday, 07:00 AM

Pfft...  The saga is not over yet...

 

I rode about 15 kilometers this morning, and sure enough, near the end of the ride it started to stall out at low revs again. No idle. Up until that point, it was running pretty crisp - no popping or anything.

 

I will check valve clearances again, but I have a feeling this is related to the throttle shaft - don't know what else to target for now. When I had the carb apart on Sunday, I greased up the shaft real good before putting it back in. The objective was to make the maximum possible seal. I am suspecting that the grease warms up, gets soft, and is progressively sucked into the carb - which clears the way for air to get sucked in instead.

 

All the same, I may be clutching at straws since the shaft didn't really seem to be loose in its bore... I have attached a photo of the only obvious wear.

 

Back to the valves - if they're tight again, what could cause that? Is it possible the new valve work is a problem? Anyway, let me not get ahead of myself. I'll go check clearances now.

 

A couple of observations relating to my post of the 20th:

 

  • The felt ring I mentioned is not on the inboard side of the carb - it is outboard. I'll attach a photo
  • My idea that a bad slide-to-bore seal would make a problem is unfounded as there are 4 holes in the bottom of the slide - equalizing the air pressure. This makes sense, because if there were none, the slide would have to compress the air above it in order to rise. I therefore don't think that a bad slide-to-bore seal will cause the problem I am having. For what it's worth, I have attached a couple of photos of the wear on the slide.

If there's nothing to report on the valves, the next test will involve running the engine without the tank on (connected, but suspended from the ceiling) so that I can do the WD-40 spray trick to check for vacuum leaks. It will be interesting to see if spraying at the throttle shaft will tell me anything.

 

By the way, there's no oil in the water or vice-versa.

 

Feel free to chip in with ideas!

 

David

Attached Files



#24 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted Yesterday, 08:05 AM

David...From the photos, I would say that the throttle shaft looks okay, the bore in the body (can't see much beyond the bore end) has corrosion, can't tell whether there is wear here.  The slide shows wear; any concern here, however, would be an air source above the slide that would supply unwanted air.  The spark plug distinctly shows running very rich or incomplete combustion

 

Is there anything unusual about the air filter or filter oil?  Could the engine be "choking" from too much oil in the air filter?  Did you buy a new OEM filter?  They come pre-oiled.

 

The WD40 test is useful and may reveal an issue.  Follow my proscription for running these quick leak tests.  I like your analysis of the slide, you can test for leakage by spraying around the slide cover at the top.  If no rpm change, it's likely not much of an issue despite the obvious wear.  I'd want to solve the erratic running condition before condemning or buying a slide.

 

Another valve clearance check is prudent, you're expert now, so that should be a brief operation.  If the gap keeps closing, and assuming the rocker adjusters are secured by their nuts, that's an indication of valve seat or face issues.  Make sure you're checking and confirming the clearance after the adjuster nuts are secured.

 

Where was the valve work done?  Do you have any idea what materials or process the shop used?  New valves?  New seats?  3-angle grind on seats?  An issue here would cause compression loss.  Cross fingers there's no issue here, the valve clearance check should help confirm.

 

You're running stock jets, right?  65 on the slow speed and 175 on the main?  The spark plug looks like actual flooding of fuel, very rich indeed.  Since the engine ran well for some of the ride then suddenly lapsed into misbehavior resulting in a fouled plug, it would seem like a sudden increase in fuel flow.  You checked the cap vent, which when malfunctioning or clogged can pressurize the fuel system and unseat the float needle.  Another possibility is either a high float level or sticking (open) float needle.  Float height and drop is important.  Too much drop can allow the needle to cock and stay unseated. 

 

Your carburetor, if like mine, does not have a drop setting.  Set float height with the body horizontal and the float's weight swinging into the needle, just enough weight to close the needle valve.  Measure height now (16mm or 0.63" to top of floats from the carburetor body's float bowl mounting surface).  Make sure both floats are even; correct and match float heights if necessary.  There were many hands on this motorcycle before your good care.

 

A caution: On this carburetor, do not invert the carburetor straight up to check float height.  If you do, the float will place too much pressure on the needle.  You'll get a false float height reading.  Overall, you want enough fuel in the bowl to keep from starving the engine.  Too much fuel will leak and also pressurize the bowl, which can richen the fuel mixture.  Do not press the needle into its seat with excess force, this will damage the needle tip.

 

Is/was there a hint of fuel seepage from the overflow vent hoses?  An excessive smell of gasoline around the carburetor?  If the carburetor is actually okay, is there something going awry with the ignition?  You share that there's no sign of misfire until the behavior occurs.  This is also when electrical parts in the stator or ignition warm up and act up.

 

As a final note/question...Did you replace or at least clean the spark plug thoroughly after the first round of fouling trouble?  Was this a fresh or thoroughly cleaned spark plug we're viewing?  An unclean plug can re-foul easily.  Is this the right heat range plug for the XR650R? 

 

Also, please share the "felt" photo you mention.

 

Moses



#25 DavidEasum

DavidEasum

    Advanced Member

  • Members
  • PipPipPip
  • 34 posts
  • LocationBurundi

Posted Yesterday, 01:45 PM

Hi Moses,

 

The "felt" picture is actually the one showing the bore of the throttle shaft. What you see is not corrosion - that's the felt. It rides in a little pressed-in copper insert. Take a look at it again and I'm sure you'll understand.

 

Indeed, I'm running a 65(S) slow jet, a 170 main. Nothing special about the air filter - it's not OEM, but it fits fine and it's not over-oiled. We have no filter oil here, so I used 2-stroke. After installation last week, there is only a small collection of drips on the bottom lip of the airbox - not enough to make its way to the little drain nipple, and certainly not enough to make it past the spark screen into the airflow. For what it's worth, I had cleaned the spark screen with gasoline and dried it fully prior to installation.

 

The spark plug was brand new in a Honda OEM box when I put the engine together. The gap was fine out of the box. I didn't pay much attention to the heat range, but I compared it to the old one and it is the same shape for the length and thickness of porcelain, protrusion of the electrode, etc. I cleaned it with carb cleaner before putting it back in yesterday.

 

The float level (rechecked on Sunday), is between 16-17 mm. This makes the line of the seam in the float pretty much parallel with the carburetor bowl mating surface before compressing the little spring tip. There is no leakage, and checking with the clear plastic hose trick has confirmed the level is adequate. The float needle is not sticking - just to be sure I used another trick on the needle orifice: brass polish on a q-tip stuck into the end of a cordless drill. The inner wall looked pretty rough before, but now it's a mirror finish and the seat is super clean. There's no weeping or smells - except when I tilted the bike over to get the fuel in the other half of the tank - thinking I may have been running out of gas.

 

The head work was done in a village in Bretagne at a race/customization/restoration shop. The place was a serious mess inside with basket cases of all kind lying around, there was even a semi-complete unrestored Indian from what I would imagine the early-mid 40s'. He had an impressive array of machine tools (that many looked to be about the same age as the Indian), and he seemed to be eminently knowledgeable. There was everything from chromed  H-D customs to the super fat-tire GSXR street dragster. The work he did was to replace the exhaust valve guides, the intake valves (for both of these items I had provided him with the OEM parts), grind the exhaust valves, and grind the 4 seats (no new seats). I also gave him new seals. I was there in the shop when he was finishing the lapping in of the valves - the loss figures seemed impressively minimal but I can't remember the specifics. I don't know if it was a simple grind, a 3-angle or a 5-angle. I know it cost a lot! (I probably could have bought a new head in the US for the same price). Can never tell if the work was done to a good spec though. 

 

As far as the compression goes, I think it's ok (not based on checking - just my feeling). I was standing at least 12 feet behind the bike at idle (this morning when it actually idled) and the puffs from the pipe were enough to muss my hair! (not that it really matters when you've just removed your helmet  :rolleyes: ). And occasionally when the auto decompress doesn't kick in, the kick starter won't budge through TDC unless you use the lever.

 

Anyway, I rechecked the valves this afternoon and can happily say that the 3 I had readjusted yesterday are all in spec. The right side exhaust however (which was in spec yesterday) is now tight. I've been turning and turning the motor over thinking that it's just the decompressor interfering, but so far I have not been able to find a spot on the revolution that puts it free again. This autodecompress thing is getting to me - I'm jealous of your decision to send it to the dustbin.

 

I know that as a result, you're not so familiar with the thing, but correct me if I'm wrong: It ONLY works on the right side (clutch side) exhaust valve, and you hear it click (it's a pretty loud click) when it is disengaging. Mine clicks - not on every revolution, but relatively often when turning by hand from the magneto bolt or the rear wheel (or the kickstarter, but I don't use that for valve adjustment). Despite the clicks, the lack of lash for the right side exhaust valve doesn't seem to change. I'll turn it some more tomorrow to see if I can get the decomp loose again (if indeed it's stuck in an activated position). If not, I'll back the rocker completely off and spin a few times to see what happens. If the decompressor doesn't back off, the only choice I'll have is to reset the lash assuming that I did it wrong before (not likely by now). 

 

More to come!



#26 Moses Ludel

Moses Ludel

    Administrator

  • Administrators
  • 1,031 posts
  • LocationReno Area...Nevada
Garage View Garage

Posted Today, 11:04 AM

David, that's not only felt, it looks like a bona fide dust seal!  If so, the seal is a good way to protect against air leaks and to keep dirt out of the throttle shaft bore and engine.  When you're able and willing, check for an air leak here.  From what you have described elsewhere, this is probably not a dominant issue.

 

As for the auto-decompressor, the right side (brake pedal side) of the engine is the exhaust valve that has a built-in arm/link for the auto-decompressor cam.  The tip-off is that the manual lever (handlebar lever decompressor) is at the left side of the rocker box, and this actuates (unseats) the left exhaust valve.

 

So, you're spot on:  The auto-decompressor valve is the one out of adjustment now.  And now I'm beginning to suspect that the auto-decompressor is "sticky" or acting up.  You've done such good work on the rest of the engine and tune, including the carburetor, that there's little chance of a flaw elsewhere.  A large clue is that the engine ran well then suddenly acted up and fouled the plug on both occasions.  This could readily be a sudden loss of compression from the decompressor unseating the right side exhaust valve.  The good news is that the right side exhaust valve (if adjusted anywhere near correctly) will not stay unseated long enough in the valve's normal opening cycle to shove a valve through the piston crown...

 

If this is the trouble, strive to free up the auto-decompressor short of my camshaft change solution.  Sticky could mean sludge or an oil flow issue in the mechanism if the springs and other hard parts are still okay.  The oil plunger plays a role with the auto-decompressor function...

 

Was this engine's oil maintenance like the rest of the previous owner/operator's maintenance?  If so, it's likely due for a serious oil system flush.  If you suspect this possibility, we'll put our heads together on a safe and suitable flushing method for this dry-sump engine.  Also, have you changed the oil filter yet, and if so, how "dirty" was the cavity around the filter?

 

A possible solution would be a high "detergent", high lubricity oil.  If you haven't drained that first fill yet, consider whether the rings have had long enough to seat.  No blue smoke and strong compression, both accelerating and decelerating, would be clues.  (Actually, with my XR650R engine, there was never a sign of blue smoke or any sensation of incomplete ring seal from the first start-up.)  After flushing the system thoroughly, consider your synthetic oil if the ring seal is now sufficient, and let's get that auto-decompressor to at least do what Honda intended.

 

The reason I chucked the idea of using the auto-decompressor was the unpredictable jamming of the kick starter mechanism and erratic operation of this device during my first days of futilely attempting to kick the engine over.  (This was when compression was absent, and I had not yet run the leakdown test that led to the top-end rebuild.)  Without belaboring the point, that was enough "auto-decompressor" for me.  Since the only possible advantage of this device is kick starting without thought or special measures, I opted out of the strategy.  Again, thanks to the '69 BSA Victor 441cc experience with 9.5:1 compression, I did know how to use a manual compression release for starting a high compression thumper.  The lesson apparently stuck, and more than 40 years later, I can kick start my Honda XR650R on one or two kicks (hot or cold so far, winter's around the corner for that test), using only the manual lever and no auto-decompressor.  I'm delighted with the Hot Cams 'Stage 1' solution.

 

If anyone is interested in booting the auto-decompressor camshaft on a Honda XR650R yet fretting over whether the engine can start readily without it, I'd be delighted to do an HD video on my starting technique.  It's highly effective and reliable, hasn't failed me yet!  We can start a new topic on that subject...

 

Moses





Also tagged with one or more of these keywords: dirt motorcycle, dirt motorcycle forum, off-road motorcycle, dual-sport motorcycle, dirt bike discussion, dirt bike how-to, dirt motorcycle how-to, Honda XR

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users