Building a motorcycle engine for reliable performance begins with careful assembly work. The Honda XR650R project came under the close scrutiny of an HD video camera, and the result is the 49:37-minute streaming video rental at Vimeo On Demand. Following the build, proper break-in of the engine is crucial.
During assembly of the XR650R top-engine, care was taken to lubricate critical parts for the initial engine startup. This included lube on the piston pin, rings, valve stems, camshaft, valve tips and timing chain—as illustrated and detailed in the video. Lubeguard Assembly Lube, Permatex Ultra-Slick Assembly Lube and Lucas break-in oil with zinc were each used accordingly. The importance of zinc additive during break-in cannot be overstated.
When a cylinder has been honed precisely like the work performed at L.A. Sleeve Company, piston ring seating is less of a concern than the camshaft break-in. Ring seating is still important, and I will describe my technique for ring-to-cylinder wall break-in:
To begin, I use a non-synthetic oil that will provide enough friction to actually seat the rings. Synthetic oil often has too much of a protective film to allow necessary friction. After break-in, I will change to full-synthetic oil and dramatically decrease ring wear by providing an extra friction barrier or film between the cylinder wall and rings.
Ring seating can be dramatically enhanced by smoothly accelerating the engine and decelerating the engine. Heavy throttle for sustained periods should be avoided for an initial timeframe (at least an hour of operation or 60-100 miles of road use). When you decelerate the engine, the piston rings push out against the cylinder wall. As noted in the video, the top compression ring for the Honda XR650R has a gas ledge machined on its upward facing, inside edge. This raises ring pressure against the cylinder wall, especially during acceleration/deceleration cycles. This increased pressure quickly seats the rings.
Caution: A sure way to prevent rings from seating is repeated hard acceleration without any deceleration cycles. Gradual acceleration, limiting peak rpm and regular deceleration cycles get the best results.
Camshaft break-in is highly significant. Damage to a new camshaft's lobes during break-in can occur quickly. The absence (deletion) of zinc from current motor oils has made this issue even more critical. (I discuss this at length in response to a Jeep 4.0L flat tappet camshaft and oil question here at the forums, read that information at the topic link.) On the Honda XR650R engine, an aftermarket camshaft from Hot Cams came with very specific instructions on initial startup and break-in. I include those concerns in my camshaft startup and break-in approach:
During upper engine assembly, Lucas break-in oil with zinc was added to the oil (poured over the camshaft) prior to startup. The amount used was based on the product's instructions, and I reduced the quantity in proportion to the quantity of oil in the Honda XR650R lubrication system.
At the first startup, the engine was run at 2,500 rpm immediately after picking up oil pressure. On the motorcycle lift and strapped upright, the motorcycle's engine was cycled between 2,500-3,000 rpm with a large electric fan in front of the cooling radiators for the first 20 minutes before idling down to 1500 rpm. (I used an infrared thermal gun to monitor cylinder, head and exhaust header heat this entire time.)
After the initial 20-minute run on the stand, the initial road/trail miles involve a cycling speed between 1400 rpm (idle) and an estimated maximum of 3,500-4,000 rpm (no tachometer on this dirt bike). I run for 20-30 minutes at a time, varying the road or trail speeds, then cool the engine completely before repeating the cycle. Make sure that your lighter on-road or on-trail use provides sufficient cooling air to the radiators and cylinder. Earlier morning or cooler evening rides are helpful.
Avoid idling for extended periods, and avoid over-revving the engine. I avoid redline shifts for at least the first 100-150 miles or 1.5-2 hours of operation. Considering the operating speeds for a four-stroke motorcycle engine compared to an automotive engine, three hours (approximately 200 miles) of concentrated effort to break-in the camshaft properly should be sufficient. Rings should be sufficiently seated now...At this point, the oil should be drained warm and thoroughly; I switch to synthetic oil now.
Note: During this oil change on the XR650R engine, I will remove the frame (down tube) oil screen (not the inside-engine screen) for inspection and cleaning. A new oil filter is mandatory; inspect the removed oil filter for unusual debris.
In the road test video, I'm on the throttle but not redlining. I don't baby (never "lug") or abuse (do not over-rev or throttle hard) an engine during break-in. Constantly monitor engine temperature and avoid overheating or extensive idling. The Honda XR650R showed no signs of "blue smoke" (ring blowby or valve guide seepage) from the very first start onward. You should not see blue smoke or significant oil consumption if the cylinder has been honed properly, the rings were installed correctly and the valve guides are sealing.
By 200 miles or 3 hours of operation, a motorcycle engine should have sufficient break-in to no longer be a critical concern. As long as oil consumption (ring blowby) does not occur with the switch to synthetic oil, the engine is ready for reasonably "normal" use—whatever that means for your riding style.
For the properly built engine, with correct break-in, a quality synthetic oil will determine the lifespan of the rings, valve guides, timing chain, camshaft, rocker arms, engine bearings, piston/pin, and other critical moving parts. Wear is greatly reduced by the use of synthetic oil. Unlike an automobile or truck engine, wear will be much more significant on a motorcycle engine that operates consistently above 3,000 rpm. Wear is all about piston travel and valve opening events, and synthetic oil can make a difference here.