There seems to be two schools of thought when it comes to breaking in your new motorcycle engine; 1) ride it gently like the manual instructs you to do and 2) ride it like you stole it. The standard way is keeping the revs (RPMs) under a predetermined limit for a given number of miles. Some break in instructions allow for an increase in the RPM limit as the miles traveled pass milestones. The second method (ride it like you stole it) is pretty much self explanatory. Ride the bike hard and rev it to redline in the lower gears.
Break in procedures and the associated warnings are in place for a number of reasons. First and foremost is the fact that all those parts that rub together must hone themselves in thereby creating a very smooth surface. This process is effectively rubbing (I'm using that term rather loosely) all the peaks and valleys that the mating surfaces have after the manufacturing process. Even if the assembly process honed every mating surface involved that would not provide any assurance that it would mate up with another part that is probably a different material and typically the opposite shape. An engine has many examples of this, for example, pistons, cylinders, piston rings, wrist pins, crank shafts, connecting rod bearings, main bearings, and all kinds of cam components. All these parts are rubbing together and depend on a smooth surface and a thin film of oil to prevent them from self destructing. Engine technology and metallurgy has changed a lot since the early days but the basic principals of smooth mating surfaces still apply.
I have heard several reasons for the manufacturer's recommended procedures including that they want to make sure that a mistake wasn't made during assembly and the gentle break in will prevent catastrophic damage to the engine. I believe the reason, apart from basic engine break in, is so that people don't push their machines to the limit for extended periods while all the moving parts are still adjusting to themselves. In other words use common sense for example warm the engine up before pushing it, no extended redline running, no low speed wide open throttle extended runs, etc. Each of these has a good mechanical reason for avoiding. In addition, BMW recommends an oil change in the first 600 miles. The main reason is metal wear.
There was a time when new or rebuilt engines would require crosshatching the cast iron cylinders in order to help seat the new rings. Today's engine use much better materials for cylinders, pistons, and rings. Since this material is so much harder it makes break in a longer process. Of course the plus side is that once everything is seated in properly you have an engine that can run for many miles with very little wear. When was the last time you heard someone complain about their engine having piston slap?
When we used to overhaul engine many years ago (cast iron block and the new thing back then was chrome rings) we would take the cars out to the highway and accelerate up to about 75MPH and then close the throttle completely until the car slowed to about 45MPH and accelerate again. We would do this a number of times in order to seat the rings in. This is nearly the same process that I use with my new motorcycles.
I push hard up to high speed of about 70 or 80 mph if I can. If I have no safe way for those speeds I still do the same hard acceleration but in lower gears to much lower speeds. Then as soon as I reach my target speed I let up on the throttle as much as I can. For example if there are cars behind me I can't totally drop throttle but I still slow down a lot until the cars approach me again and I repeat the process. The reason for hard acceleration is that it places a much greater force on all the piston and crank shaft parts. Accelerating increases piston side thrust pressure and the combustion force increases the pressure on piston rings also. The deceleration process is just as important. When you close the throttle at high engine speed you are creating a negative pressure in the combustion area. This negative pressure wants to suck oil into the combustion chamber. It wants to suck it past the piston rings and even the valve guides. This action serves to lubricate and cool those parts. It's the breather they get after they were pushed hard in the acceleration process. This procedure is very different from that of holding the throttle open for an extended period of time. Doing that is never recommended - new or old engine. That's the reason race car engine need overhauling so frequently especially drag racers. Also note that I don't approach redline with this procedure - at least not with the RT but I did with my ST1300.
I'm not sure if this can still happen with modern engines but a caution used to be that an engine had a short time to properly start the break in process. If not followed properly the risk of glazing cylinder walls existed. Once this happened further break in could not take place. Someone had to tear the engine apart again rough up the surfaces again and new rings installed. Worn rings would not seat as fast or as well as new rings. The rule was don't baby the new engine. By the way, brake shoes used to glaze over also and that would render them nearly useless for stopping the car.
I'm one of those guys that never had a bike use oil including my current 2010 R1200RT. Recommended oil changes are 6K miles but I have gone 8K miles between oil changes twice because of extended tours of over 4,000 miles and the engine has never needed oil. The riding conditions always include high speeds, heavy loads, and lots of climbing - all conditions that increase oil consumption.
|A cool 36 F in June
This is the procedure that I use. I am not saying anybody else should use it. As much as we pay for these bikes we should be careful with them. I'm simply sharing what I do and why.