And another good one.
Most people seem to operate on the philosophy that they can best get their money's worth from any mechanical device by treating it with great care. This is probably true, but in many cases it is necessary to interpret what great care really means. This is particularly applicable when considering the break-in of a modern, reciprocating engine.
For those who still think that running the engine hard during break-in falls into the category of cruel and unusual punishment, there is one more argument for using high power loading for short periods (to avoid excessive heat) during the break-in. The use of low power settings does not expand the piston rings enough, and a film of oil is left on the cylinder walls. The high temperatures in the combustion chamber will oxidize this oil film so that it creates glazing of the cylinder walls. When this happens, the ring break-in process stops, and excessive oil consumption frequently occurs. The bad news is that extensive glazing can only be corrected by removing the cylinders and rehoning the walls. This is expensive, and it is an expense that can be avoided by proper break in procedures.
We must achieve a happy medium where we are pushing on the ring hard enough to wear it in but not hard enough to generate enough heat to cause glazing. Once again, if glazing should occur, the only remedy is to remove the effected cylinder, re-hone it and replace the piston rings and start the whole process over again.
We asked four top motorcycle engine builders what they do to ensure peak power output and optimum engine life. Here is a capsulation of their responses.
"If the wrong type of oil is used initially, or the break-in is too easy, rings and cylinders could (read will) glaze and never seal properly. A fresh cylinder wall needs some medium to high engine loading to get the piston rings to seat properly for good compression but make sure you don't lug or overheat the engine. Use high quality, low viscosity oil (Valvoline 30 weight), no synthetics, too slippery. If synthetics are used during initial break in the rings are sure to glaze over.
An engine's initial run should be used to bring oil and coolant (air, oil, and/or water) up to operating temperature only, with little or no load, then shut down and allowed to cool to ambient temperature. This is important. After each run the engine needs to completely cool down to ambient temperature. In Texas, especially in the summer, that's still pretty hot. After a cool down period, start it up again and take the motorcycle for it's fist ride (you hope).
This time give the engine light loads at relatively low rpm and stay out of top gear. Lugging the engine, i.e., low RPM with a lot of throttle (manifold pressure), is more detrimental than high rpm. Another key is too constantly vary engine load during the entire break-in period. A constant load is not ideal for breaking in bearing tolerances. This second run should last only 10-15 minutes before another complete cool down.
The third run should see slightly higher rpm with light to medium power loading using short bursts of acceleration to help seat the rings. Again 10-15 minutes of running should do it and again avoid top gear. A forth run should consist of light to medium engine loads with a few more bursts of medium-high rpm, and lasting just 10-15 minutes varying the engine load and again avoiding top gear. Next while the engine is still warm drain the oil and change the filter. This gets out the new metal particles that are being worn away. Most of the metal particles will break away within the first 50 -75 miles. To ensure the rings seat well, use the same high quality oil and don't be shy about short duration high rpm blasts through the lower gears after the oil has been changed.
A few more 15-20 minute sessions should be used to work up to the engine's redline gradually increasing the engine loads. After some definite hard running and 250-500 miles it's a good idea to check the valves. After 500 miles re-torqueing the head is suggested. Switch to synthetic oil but not before 500-1500 miles. Most of the engine experts warned of the danger of breaking in the engine too easily and ending up with an engine that will always run slow whether it is from tight tolerances, inadequate ring seal or carbon buildup. Engine load is more detrimental than rpm because of the head created internally, so avoid lugging the engine but rev it freely especially in the lower gears. Basically, be sure not to get it too hot but be sure to seat the rings properly.
So that's it, sure a lot different than keeping under 4000 rpm for 500 miles then under 5000 rpm for 1000 miles. Maybe bike manufacturers are being super cautious at the expense of your motor's performance? I think that they take the cautious route that works over time (1000 miles, or about 20 hours of break in) versus a faster route that can be more easily screwed up."
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