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Kawasaki KLR Motorcycle Engine Teardown and Inspection

off-road motorcycle dual-sport motorcycle motorcycle forum dirt bike forum dirt bike troubleshooting dirt bike how-to thumper motorcycle

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#1 forman

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Posted 04 February 2014 - 10:37 AM

I pulled the oil filter and passed a large magnet over it but I did not pick up any ferrous metal.  The close up photo of the filter reveals many small chips of aluminum.  Well all I have to do is open up the motor and start looking for a bright shiny spot!

 

This is the filter out of the 2006 salvage bike.

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#2 Moses Ludel

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Posted 04 February 2014 - 01:50 PM

If the crankshaft was pressed apart and a new or used rod installed, there could have been a balance issue with the crank assembly.  Also, the flyweights must align perfectly, or the entire crankshaft assembly will want to swing out of center, which can tear up the case. 

 

We'll see what you find, Forman.  Also, keep moving parts balance in mind when doing the reassembly.  You don't want another 100 mile ride to serve as the engine's lifespan.  Matched parts or subletting a balance job on the crankshaft assembly would be worthwhile.

 

I thought more about your cylinder head work.  If the casting is damaged and there is severe valve seat recession, most single cylinder motorcycles get a new head.  Honda castings are in the $300-$400 range, you're creative with used parts, and it sounds like there are plenty of KLR pieces out there.

 

This discussion is bringing back a flood of memories.  When I worked construction and as a heavy equipment operator and repairs in the early 'seventies, I "followed my passion" on the side and opened an independent motorcycle repair shop.  Though my forte was British motorcycles, I magnanimously worked on anything that came through the door, a good business move for a small town.

 

The Chrome Horse was a fun and challenging venture.  Alongside BSA, Triumph, Norton and other British marques, this was the era of vertical shock dirt bikes, two- and four-stroke, plus the hot street two-strokes like the Kawasaki HI and H2, two totally lethal motorcycles good for nothing but straight line drag racing.  Honda had revolutionized the industry with the CB four-cylinder engines.  I was "in my element" as we say! 

 

I worked on OHC Honda engines of the day and was always fascinated with the Japanese ability to machine precisely—regardless of casting appearances.  The capper for me was mating two used and foreign case halves for a Honda CB350 without a bit of oil seepage or any measurable misalignment.  Says much for Honda, though the appearance of frame welds were another story at the time.  In fairness, they did hold.

 

Attached File  Chrome Horse (1) (640x517).jpg   178.72KB   0 downloads Attached File  Chrome Horse (2) (640x506).jpg   162.82KB   0 downloads

This was my life before four kids (now a bunch of grandkids, too), a fancy college degree from the University of Oregon and decades of chasing the brass ring (American Dream, take your pick of euphemisms!).  The Chrome Horse at Carson City was my independent motorcycle side business while working construction and running heavy equipment at northern Nevada in the early to mid-'seventies. Motorcycles have been in my life for a half century now, my first operator's license was at age 14, a Nevada Scooter License.

 

Funny how some passions stick around!  Donna and I have been married for 37 years.

 

Moses



#3 forman

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Posted 04 February 2014 - 06:39 PM

Moses you have done many things with your skills. I know that I speak for others also when I say Thanks for being here I appreciate your expertise.  Sounds like you had fun along the way!

 

 A used motor was the donor for the crankshaft connecting rod, piston and cylinder.  Nothing was taken apart any further than it had to in order for it to be placed in my salvage bike engine case.  I mentioned more vibration than my other KLR and that is true but I really need to describe it as a buzz rather than a rumble.  I feel certain that the counterbalance weights were aligned correctly.  The head was in great shape when I received it and the valve clearances were spot on.  

 

This afternoon I pulled the oil filter and found a large amount of small aluminum debris, while it was not enough to clog the filter I was concerned that the camshaft journals might have suffered some damage.  After work I stripped my bike to allow access to the valve cover and opened it up to inspect. I've included some photos of that process.

 

A first generation KLR is easy to work on especially if there are not any cosmetics to remove... Thanks to a bunch of thieves it is really easy to get to the engine.

 

By removing the seat, gas tank, 3 bolts on the radiator fan, the upper engine mount, the coil, spark plug wire, the valve cover bolts and finally removing the cover up and over the cam gears the whole head is exposed.

 

I removed the journal bearing caps and lifted the cams to reveal that there was no visible damage... whew!  seen in the last photo

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#4 Moses Ludel

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Posted 04 February 2014 - 06:55 PM

Umm, Forman, that's quick work to discover very clean journals...So, where's the aluminum chafing off?  Looking forward to your further diggings when time permits...Oil pump?  Chain sweep?  Where?

 

Keep us posted!

 

Moses



#5 forman

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Posted 07 February 2014 - 05:34 AM

It has been too cold to work in my garage so I've had some time to think about what I would like to do next.  I'm looking for aluminum damage.  The head is made of aluminum and I've yet to pull it off and look at its underside, but for some reason I feel confident that it is fine and that would cost me a gasket to check it out.  The piston is made of aluminum, but I'm not ready to go there yet either.

 

On KLR's the timing and cam chains are located on the left side, if you remember I mentioned that the vibration I felt was more of a buzzy type that a chain to metal friction area might produce.  Armed with this bit of reasoning I will attack the left side of my engine when the weather permits.  I will need to remove these side plates anyway if I need to go deeper into the crankcases.

 

Here is a photo I took while tearing down the engine a few months ago that shows what I will be looking into.

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#6 Moses Ludel

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Posted 07 February 2014 - 10:09 AM

The chain issue was my "chain sweep" comment...This could be your culprit. 

 

Does Kawasaki use a hydraulic chain tensioner?  If so, it could be starved for oil.  Even spring tensioners can bind.  Good place to consider...If you get off that easy with only light chafing of the aluminum by the chain, there's the need to ride out the debris issue. 

 

Don't try flushing the system with the oil screen removed, you're better off letting the screen and oil filter do their job.  If you flush through with the engine together and screen removed, that aluminum will be scattered throughout the oil system.  Vital parts would be vulnerable.  As you saw with the cam journals, the oil screen has worked thus far.  Of course a clogged screen restricts oil flow, so be vigilante about screen cleaning and filter changes until all debris is gone...

 

Keep us posted...Your pics are great, Forman, you have a knack for the right camera angles!

 

Moses



#7 Moses Ludel

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Posted 07 February 2014 - 10:13 AM

Looked closer at your photo...Has the primary chain jumped off its sprocket?  Did you loosen it, or was it setting off the gear when you pulled the timing cover? 

 

I'll get a KLR engine cutaway illustration as we delve further.  Would like to be in step with the engine design and your findings.  My first round with a KLR powerplant, I'm intrigued.  What year is the engine, again?

 

Moses



#8 forman

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Posted 07 February 2014 - 10:56 AM

Sorry I should have clarified that the photo was taken prior to the last rebuild.  The engine was a wreck.  a spring loaded tensioner is used in this 2006 engine.  The engine is basically unchanged from '86- 2007.  That isn't completely true I should say from '96 -2007 and possibly to the present model (I'm just not familiar with the generation 2 model that came out in 2008).



#9 Moses Ludel

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Posted 07 February 2014 - 06:50 PM

Clarifying...So, we're now looking for the cause of aluminum sloughing in a 2006 engine with 100 miles since major work?

 

I can get parts schematics online, we'll be in step as you proceed...I'm earnestly interested!

 

Moses



#10 forman

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Posted 08 February 2014 - 08:45 PM

Yes Moses you are right, and my hat is off to you for the video work you do.  All the work involved in getting a video published is much harder that the actual work!

 



#11 Moses Ludel

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Posted 08 February 2014 - 11:21 PM

Forman, it "only" took me four years to get on top of the filming and post-production editing with HD video.  That was after a career at photography and journalism that spanned three decades and involved somewhere in the neighborhood of 16,500 published photos.  My gut sense is that HD video is the new journalism.  Video is easier to understand as 24, 30 or 60 fps shooting of frames, which demands slow and smooth panning...Post production editing has a steep learning curve and takes significantly more time than the initial filming.

 

That said, your video (above) is great and ideal for other forum members and guests!  Thanks much for taking the time to present this work, you follow OE guidelines for removing the rotor and accessing parts without damage.  The pawn shop wrench with "custom" offset is very slick, a great solution for the recessed and two-flat metric bolt!  The chain does look okay, and as you note, this is not yet the chafed aluminum source.

 

I like your work style, others will prevent damage by following this well done video.  If you care about the wind noise: I filmed plenty of videos with wind noise early on!  I use an external mic with a wind sock.  You may be able to improvise, even if you're using a built-in condenser mic.  The aim is to keep direct wind out of the mic while not squelching out all sound...Great job on the narration, Forman!

 

Moses



#12 forman

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Posted 09 February 2014 - 02:00 PM

The right side inspection.   

 



#13 Moses Ludel

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Posted 09 February 2014 - 05:07 PM

Another great video, Forman!  The clutch holding tool is both innovative and practical.  I've used a Snap-On strap wrench successfully, especially with an air impact for removing the nut or bolt...The aluminum "paste" sounds like typical fine wear from the clutch plate teeth in the hub splines, not your major aluminum sloughing.  The filter shown has somewhat large aluminum chips in it.

 

You've done the heroic, the engine is now on the bench.  I'm curious to see the piston at this stage, something that could scarf or slough off aluminum.  Needless to say, if removing the head and barrel does not quickly reveal trouble, you will be looking deeper into this engine, at the crankcase and bearing seats/bores.

 

I'm thinking possible piston ring trouble, maybe broken rings clawing away at the cylinder wall...Won't be long now before you locate the trouble spot.  We'll discuss the problem source and cause when you reach the damage!

 

Moses



#14 forman

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Posted 09 February 2014 - 06:52 PM

I worked with the motor on the bench today, my garage is dimly lit so videos were out.  I was able to split the cases and take a quick look but I found no damage spots, I will look closer while cleaning up, along with double checking diagrams to ensure that I built it right the last time.

 

The top of the piston and underside of the head had a lot of carbon build up for only 100 miles of service.  A quick look as I was disassembling showed intact rings and a clean bore with no oil tracks.

 

Then again the metal flake could have been residual from the original rebuild that just didn't get flushed properly.  No problem I needed to address the carbon buildup problem anyway.  

 

What do you think Moses? 

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#15 Moses Ludel

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Posted 09 February 2014 - 09:21 PM

Once again, the photos are helpful, Forman...This engine was either lacking compression seal or pouring oil down the valve guides past the guide seals.  Let's look at the cylinder wall crosshatch honing.  You need to test valves for seal.  A quick and simple test with springs in place is to simply pour solvent carefully into each exhaust port and intake port with each port facing upward as you pour.  You're looking for valve to seat seal.  This will also locate a valve to seat leak point.  Make sure there's no carbon under the valve faces when you perform this test...

 

If not guide/seal oil seepage, you may have poor compression seal, either valves and/or rings, possibly the head gasket.  You'll want to check the piston-to-cylinder wall clearance.  If the rings are intact, carefully remove them and check ring gaps with the ring setting squarely in the cylinder. 

 

Looking forward to some clear photos of the cylinder, piston, rings, valve faces and valve seats when you get to that point...Did you replace the valve guide seals?  That could be a source of oil in the upper cylinder, especially if the valve guides show any wear.

 

Moses



#16 forman

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Posted 10 February 2014 - 04:58 AM

I will get some photos up today.  

 

The head was professionally rebuilt I knew that replacing one valve face, the two exhaust rod guides, and two bent valves would surpass my skills.  Valve seals were replaced with Viton seals.

 

I do not have the tools to measure the piston or inside the cylinder... I will work on that though, any recommendations?  The inside of the cylinder where crosshatching should be is like glass, The rings were just within specification.  I do not know the history of this piston and cylinder, they were from a donor engine that I bought off of craigslist that was supposed to have only 4000 miles.  

 

I realize that some of my choices while rebuilding this engine were inconsistent for instance I replaced all bearings and seals instead of just the obviously bad ones.   While I bought a donor engine and used the cylinder, crank and piston without refurbishing the used parts, my skills were lacking and I chose to slap those parts in and move on.  That is why I am in the situation I am in now.  

 

I am confident that with your help I'll get this engine running like it is supposed to. Then again that is why I bought the $100 dollar engine with the stripped oil plug as a possible replacement. 



#17 Moses Ludel

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Posted 10 February 2014 - 10:39 AM

Thanks for being thorough in describing work done and not done, Forman.  Some are hesitant to note issues they create, which makes troubleshooting from a distance that much more difficult...Unless the head has become damaged, Forman, it should be okay.  Do the quick seal test with solvent as I recommended, anyway.  That's a rough check for valve seating.

 

When you share that the cylinder looks like "glass",  I'm concerned.  No damage, scoring or gouges is good; no honing crosshatch to seat the rings and maintain oil on the wall is not good.  Your pending photos of the cylinder will help me assess this further.  If the cylinder is glazed badly, the rings were not sealing, which would account for the major oil blowby into the combustion chamber.

 

As for measurements, if you do not have an inside and outside micrometer set, piston-to-wall clearance can be checked with a blade feeler gauge.  You're working around the 0.002" or so blade thickness or metric equivalent.  In the shop manual, there should be a spec for piston clearance.  With the rings removed (carefully, to preserve them if still intact and usable), measure the space between the piston and cylinder wall. 

 

Make sure the piston and wall are clean and free of any debris.  The piston should be slightly "snug" when measuring with the correct blade.  The easiest approach is to place the blade against the cylinder wall and slide the piston alongside the blade.  Don't force the piston if the blade is too thick, start thin and work your way to the correct thickness blade.

 

You will always get an optimal measurement between the piston and lower portion of the cylinder, as that area is unworn.  Compare this with the upper cylinder measurement below the "ridge".  The ridge is the unworn area above the top piston ring's travel.  You want a maximum wear measurement, and this is where the upper piston ring stops.  Cylinder walls "taper" toward the top of the piston travel.  The highest cylinder wear and largest diameter is just below the ridge.

 

With an inside micrometer, of course, you could compare the cylinder diameter at several points on the wall.  When measuring the piston diameter with an outside micrometer, or when checking the piston-to-wall clearance, always measure 90-degrees from the piston pin centerline.  Wear will be at the thrust areas of the piston, perpendicular to the pin.  The piston wears here due to the load points.  This is also why the piston skirts are located here.

 

Note: Some pistons are cam-ground and not round to begin.  Cam-grinding or "oval shaped" pistons compensate for the heat at the pin bosses.  Pin boss heat requires slight room for piston expansion at this area of the piston. 

 

We'll look closely at the piston skirts and see if that's your grating aluminum source.  Still haven't found the cause of aluminum grit in the oil screen, though this could go back to debris in the oiling system from earlier engine damage.

 

Moving forward...

 

Moses   



#18 Moses Ludel

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Posted 10 February 2014 - 11:01 AM

Forum member Forman found aluminum filings in his Kawasaki KLR motorcycle engine after a recent rebuild.  He is now undertaking a complete engine tear down, inspection and the proper rebuilding of this low-mileage engine.

 

Follow Forman's work and our discussion as this engine comes apart.  His steps follow factory procedures and "good practices"...The goal is an ultra-reliable Kawasaki 650 KLR dual-sport motorcycle!

 

Moses



#19 forman

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Posted 10 February 2014 - 02:51 PM

The cylinder wall at first appearance was very shiny with a glazed almost mirror finish.  My photos show that cross hatch markings are visible as well as several other inconsistencies in the metal like small pitting hardly visible to the naked eye, also some minute travel markings left by the rings as they rode up and down the cylinder wall.

 

The last photo is a really cool looking close up Attached File  close cylinder.1.jpg   89.53KB   0 downloads

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#20 Moses Ludel

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Posted 10 February 2014 - 05:11 PM

Forman, the photos are outstanding and conclusive:  poor cylinder seal, enough to cause the oil blowby that you found on the piston crown and combustion chamber.  Cause of the cylinder wall damage looks like fuel wash, i.e. either too rich in fuel mixture (now or before your rebuild) or overheat.  I'd suggest the rich fuel mixture, which causes fuel washing of lubricant from the cylinder.  This can happen when compression drops and the engine gets driven still.  Low compression makes for poor combustion and rich running—so does operating the engine with the choke stuck on.

 

A cylinder leak down test before this tear down (see my video and article on that subject) would have shown major compression leakage around the piston rings.  There is now no appreciable crosshatch to seat or seal the rings, and oil cannot stand on this cylinder wall without crosshatch.

 

If this is Nikasil, you may have a long shot for honing.  Honing would best be done by an automotive machine shop with a Sunnen or similar power hone that can keep true and make the cylinder round at the same time.  The machine shop can determine whether there is enough Nikasil and bore diameter left for honing with the current piston (if this piston is still okay).  I see both cylinder glaze and pitting, scoring as well.

 

On my Honda XR650R, I took the next step and passed on Nikasil.  L.A. Sleeve is boring the cylinder and installing a patented alloy iron/moly-chrome cylinder liner at the correct bore size, precisely honed for the new piston size and rings.  In my case, I stayed with a cast (OE replacement upgrade) piston at the stock 10:1 compression ratio (plenty, thanks!), quality matching rings and gaskets.  I'll likely install a Hot Cams Stage 1 camshaft during my assembly work...Will explain that choice during my assembly work.

 

This kind of expense may not be what you want to hear.  The machine shop measurements and assessment of the cylinder, piston and bore size will help determine your next move.  (Please post photos of the piston and rings.)

 

I sigh when "good used" parts come up online at Craigslist and eBay.  "Good" and "used" often become an oxymoron.  eBay seems to provide more recourse, Craigslist is a crapshoot in my view, I've done well and not so well on Craigslist.  Got lucky with the Honda XR650R; the previous owner truly did not anticipate the damage I discovered.  He made equitable recourse, too.

 

Your cylinder damage could be the result of running the engine with the choke on, too, long before you rode the bike or when it got "borrowed".  Regardless, the damage is apparent, there was no possibility for piston ring seal—even 100 miles of riding was too much for this cylinder, piston and rings! 

 

Still would like to pinpoint the aluminum debris source, it could have been embedded in the oiling system from cylinder wear and severe piston damage.  A bent rod would have cocked the piston, causing the aluminum piston skirts to wear radically—in a hurry!  Do you still have the piston?  Would like to see the skirts...Also, you mentioned bent valves.  This engine may have been downshifted at a high rpm, floating the valves and causing them to interfere with the piston.  This can bend a rod.

 

Sound plausible?

 

Moses



#21 forman

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Posted 10 February 2014 - 07:06 PM

A shot of the interior right side crankcase no small pieces of aluminum.

Attached File  2006klr_028.jpg   189.24KB   0 downloads

 

The piston

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I was trying to photo the skirt bottom to show wear if present

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The next shots show some wear on the skirt but minimal I think

Attached File  2006klr_032.jpg   97.19KB   0 downloads  Attached File  2006klr_031.jpg   102.32KB   0 downloads

 

The ring gap was out of spec and nearing the service limit on both rings.

 

I think this is a cast iron cylinder a stock KLR cylinder

 



#22 forman

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Posted 10 February 2014 - 07:37 PM

Moses in this photo the pitting or erosion is very evident but while looking with the unaided eye this looks like a stain on the cylinder wall.  I'm thinking that the microscopic pitting maybe normal to some extent.  I know that LA Sleeve claims to make a better cylinder out of better material and also several KLR owners complain of out of round cylinders that wear abnormally and loose compression.  Just thinking out loud... 

Attached File  IMG_1035.JPG   67.1KB   0 downloads

 

I've got the original cylinder the grenade went off in I'll take a closer look at it tomorrow.



#23 Moses Ludel

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Posted 10 February 2014 - 07:58 PM

The last piston photo shows score lines that match those on the cylinder wall.  There is no significant damage, and if you're on a tight budget and can get a light honing to work, with proper piston to wall clearance and a round cylinder, this piston might be salvageable.  Is this the original piston and rings?  If so, you have a shot here.

 

You're back to measuring the cylinder accurately and judging whether there's room for a hone job to restore crosshatch without running outside the bore diameter limit for the piston.  If this is the stock piston, there may be room for a restorative approach using a new, zero-wear piston.  This, again, is all dependent on the piston to wall clearance.

 

     Note: Here's one more way to measure the cylinder roughly without an inside micrometer:  Take the compression (top) piston ring, and measure the end gap at several places in the cylinder, comparing the gap size.  Keep the ring level while taking each of these measurements.  If consistent and uniform, you may have a round and serviceable cylinder—if within bore diameter specifications.

 

If you can confirm the measurements for the cylinder, piston and estimated ring gap with a new ring, we can talk about your doing the cylinder honing yourself.  Before you attempt this task, the cylinder would need to be round, with negligible taper, and simply needing a hone job .  I can clarify....

 

If you do decide to replace the piston, I would consider having the cylinder brought to the first oversize if this is iron.  (Nikasil is another story, it's a plating and cannot be bored; it can be re-honed if that's sufficient.  Otherwise, re-plating is necessary.)  If you can reuse this piston, spend some time with Scotch Brite lightly polishing the score line areas.

 

Once again, your photos are very helpful, Forman, well shot with good exposure.  Nice detail, too!

 

Moses



#24 Moses Ludel

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Posted 10 February 2014 - 08:15 PM

The extra pitting photo is sharp and revealing, Forman.  The pitting is through what faintly remains of the original crosshatch.  It's also on a uniform plane and looks like corrosion from moisture at the cylinder wall, likely with the piston parked at a specific point in the cylinder for an extended period of time.  Stored motorcycles, especially at humid climates, often show this kind of pitting.  Covering the bike with a tarp can cause even more trouble, although the cycle does need to be out of the weather.

 

Would be surprising if Kawasaki builds an out-of-round cylinder, more likely this is a common wear pattern for these engines.  Depth of the pits, on your cylinder, would determine whether this bore will work or if re-boring is necessary.  The mere fact that this is pitting means the liner is iron.  Nikasil would be more corrosion resistant.

 

First oversize is typically .25mm or approximately 0.010".  At that bore and new piston oversize, the engine should still run cool and deliver great horsepower.  I would check the carburetor jetting and needle position if you suspect any changes have been made.  I will be covering tune issues when I get the XR650R upper engine back together soon.

 

Moses 



#25 forman

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Posted 24 February 2014 - 05:35 AM

Its been awhile since I could focus my attention to this engine.  I've been cleaning and inspecting not only the parts but my previous work.  So far I have found that all parts were assembled correctly.  I mentioned earlier that this engine was so completely wrecked and there are abrasion marks inside the case from the wreck previous to my last rebuild that prevent me from being able to pinpoint the source of fine aluminum flecks that I found in my oil.  The particles could have also been from an incomplete cleaning that I gave the engine parts, I think especially the clutch parts.  I don't think I'm going to be able to find the source if it exists.

 

I was able to measure with a dial caliper across the piston skirt as per the KLR manual and determine that the piston has exceeded its service limit and must be replaced. This also means that I will need to bore the cylinder if I choose to use this engine.  I placed the parts in the crankcase and took a few photos...  

 

The two case halves

Attached File  06 rebuild_001.jpg   154.05KB   0 downloads

 

The transmission input shaft (left) and output shaft

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The input and output shafts shift forks and shift drum in place

Attached File  06 rebuild_003.jpg   156.41KB   0 downloads

 

The right crankcase half with all components in place Attached File  06 rebuild_004.jpg   165.28KB   0 downloads

 

 



#26 Moses Ludel

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Posted 24 February 2014 - 09:59 PM

Your usual great photos, Forman...No "major" damage evident, some wear visible but nothing serious.  The piston measurement was revealing.  Is there piston skirt aluminum sloughing or any skirt damage to the cylinder bore?  I recall severe glazing, but is the bore out of shape?  Were the piston skirts dragging the wall?

 

If not, this is as you say, an engine with accumulated debris.  Flushing passageways would be worthwhile if you decide to rebuild completely.  What kind of piston-to-wall clearance were you experiencing here?

 

Moses



#27 forman

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Posted 25 February 2014 - 04:38 AM

I'll have an inside micrometer available to me later this week.  I do want to finish this rebuild knowing that most likely it will take a overbore kit.  If you remember we started this thread after I bought a lower mileage engine with a cracked case.  I should have photos of that damage tonight, I'll post on the engine case thread started earlier



#28 Moses Ludel

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Posted 25 February 2014 - 10:31 AM

Great, Forman!  After measuring the piston and cylinder, we'll outline the findings and factory recommendations from your shop manual...As a wrap-up for the "inspection" phase, it would be good to show piston to wall clearance and the ring end gaps in this loose cylinder.

 

We can start a new topic as you "rebuild" the upper end of this engine and perform related work: "Kawasaki KLR 650 Engine Rebuild" would be a good working title for the topic, you have the entire engine apart now...Your photo/video documentation has been valuable.  It's time consuming and appreciated.  

 

This is valuable to KLR owners and others...some consolation despite the work and cost involved!  Once done right, you'll have a reliable motorcycle that is quite desirable, the KLR has a strong following.

 

Thanks!

 

Moses  



#29 forman

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Posted 02 March 2014 - 06:00 AM

I've acquired a good inside micrometer, and was able to measure the inside diameter of this cylinder. I was also able to measure the ring end gap, and the piston outside diameter.  Keep in mind this cylinder and piston were bought off of craigslist and I can't explain why these measurements  seem odd. I'll refer to this cylinder as the '98 cylinder.   

 

Cylinder inside diameter  3.936     factory specifications (3.937-3.9374)  service limit 3.9409   I measured this cylinder in 20 different places I never got a measurement over 3.936.

 

Piston outside diameter   3.924     factory spec               (3.9347-3.9353)  service limit 3.9291  The piston has exceeded its service limit by .005"

 

Piston to cylinder               .012     factory spec               (.0017-,0028)   Its easy to see why I was burning so much oil  but I can't explain the power I felt.

 

Ring thickness                N  .0455     2N .0455                 (.0461-.0469)  service limit  .0430

 

Ring end gap                  N  .018       2N .016                   (.008-.016)  

 

Why the piston is so far gone and the cylinder has room for wear is beyond me I suspect some used parts were exchanged before I bought the engine.  The piston and rings will need to be replaced but the cylinder might be repaired by honing.   

 

Moses you had asked previously what jets were in the carburetor :  Stock main jet below 4000' elevation is a 148 mine is a 150 we are at 2000 feet.  Pilot jet and needle jet are stock and rated for my elevation.  My exhaust is a straight open pipe I don't know the brand name but it is not stock.



#30 forman

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Posted 02 March 2014 - 06:19 AM

I have the luxury of having another piston and cylinder, This is off of the '02 engine with the cracked crankcase.  The previous owner said it used oil and the piston had a thick layer of carbon build up.  

 

Cylinder inside diameter    3.937     (3.937-3.9374)              service limit  3.9409

 

Piston outside diameter     3.934     (3.9347-3.9353)            service limit   3.9291

 

Piston to cylinder                .003     (.0017-.0028)

 

Ring thickness                   N   .046   2N  .046     (.0461-.0469)

 

Ring end gap                    N   .012    2N  .013    (.008-.016)

 

I know my problem can be solved by installing an overbore kit, one I'm looking at will run about $450 with new forged piston, rings, gaskets,machine work and shipping.  I would like to save some money and hone the cylinder myself but I really don't know what tools, parts and technique that would require.



#31 Moses Ludel

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Posted 04 March 2014 - 10:23 AM

Hi, Forman...Good work here...The piston is shot, that's clear, and the piston to wall gap is extreme, the cause, as you note, for the loss of oil control.  That and the cylinder not having a good cross-hatch pattern led to lack of cylinder seal.  A cylinder leakdown test would confirm.  (See my leakdown test video at the magazine site.)  These motorcycle engines have high compression ratios, and the compromised performance from poor cylinder seal is not always that noticeable, perhaps the reason the engine "felt strong".

 

I am puzzled about one reading:  ring end gap.  If those rings (#1 engine) were new, the gap should be less than the 0.018".  Your cylinder bore diameter is normal from your readings, yet the ring gaps are out of range.  When you do the ring gap check, make sure the ring is perpendicular to the wall and level.  This will keep the measurement accurate.  Measure below and above the "ridge".  Likewise, when you measure bore diameter with an inside micrometer, try to keep the mic level and also at the widest point in the diameter (typically right below the ridge).  This can be tricky to do, but you will get a more accurate read.

 

So, you're considering a big bore kit with a forged piston.  Be aware that a forged piston, though optimal for racing, does call for more piston-to-wall clearance.  On my XR650R Honda beast, I am staying with a cast piston (OE type) and quality rings.  The new cylinder sleeve from L.A. Sleeve is an iron/alloy (chrome/moly) that is spot on for bore diameter and piston-to-wall clearance.  The liner has a very nice machine cross-hatch, which I will be highlighting soon in an HD video during assembly...Forged pistons can be a bit noisier when the engine is cold.  Also, I stayed with a stock 10:1 compression ratio on the XR, while most forged pistons bump up the compression; this makes power but also impacts engine life and can be a cause of detonation (ping) unless you run spendy, high-octane fuel...Just some thoughts.  We can kick this around...

 

Your jetting may be rich enough for the open exhaust (uncorked), especially at your altitude.  Try to confirm the exhaust maker and research their jetting recommendations for the "uncorking".  On the XR650R, uncorking (intake manifold and air box improvements plus exhaust) requires a change from the 125 main jet (ultra-lean stock) to a 175 main at sea level.  This is a huge bump, but the XR650R OE jet is way too lean for openers...a U.S. EPA concession on Honda's part while the overseas carburetors are 175 main jet in stock form!  We're based at 4400 feet elevation, I ride to 6000 feet or higher often, and I'll first try a 172 main jet with the open exhaust and freer flowing induction.

 

Moses



#32 forman

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Posted 04 March 2014 - 10:58 AM

Lets just say the first cylinder piston is a wash and a great candidate for the overbore I spoke of.  

 

What about freshening up the cylinder and re ringing the '02 cylinder?  I have never done this or seen it done so I'll have many questions



#33 Moses Ludel

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Posted 04 March 2014 - 12:57 PM

If the cylinders are interchangeable, that's a clear option.  I would spend the relatively small amount of money to have the cylinder power honed at an automotive machine shop to get a precision cross-hatch for oil control and compression seal.  If the '02 piston is on spec, that's a possibility, a new cast piston is not terribly expensive.  (There are new cast pistons in slight oversize, too, if honing goes wide.) 

 

Get the piston first for fitting while the machinist hones.  Ask his opinion about the right piston to order.  Do this once, I'll gladly walk you through this process to a successful end...

 

Moses



#34 forman

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Posted 04 March 2014 - 02:59 PM

Finding that machine shop might be the most difficult part...



#35 Moses Ludel

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Posted 05 March 2014 - 07:58 AM

Forman, you're looking for a traditional automotive machine shop that does cylinder boring and honing.  In rural and semi-rural communities, these shops were often associated with NAPA stores and other retail parts outlets.  At your area, try the Yellow Pages under "Automotive—Machine Shops".  Also, some larger motorcycle shops have boring and honing equipment, a Honda, Kawasaki, Yamaha or Harley-Davidson shop might be helpful here.

 

You're looking for a shop that has a CK10 Sunnen or similar boring and honing machine.  This is the classic tooling for automotive block work.  There are some smaller machines for lighter engines. 

 

I can describe in detail how to use a "glaze buster" silicone honing brush or a three-stone hone, I have used these tools for years.  They are for light honing and glaze removal and can leave a decent cross-hatch pattern if used precisely.  You run these tools from a common 3/8" or 1/2" drill motor, or a drill press if set up properly.  If your cylinder is true and not measurably tapered, you can get by with a home honing job when done correctly.

 

See what you find for a local machine shop.  If you'd like to hone the cylinder yourself, let me know.

 

Moses





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