I have been looking for information on good run in techniques but haven’t found any so far that actually manage to explain WHY they work. And they few people that claim to have found a magic method usually fall flat on their face when they start to explain it. Before people get me wrong, I don’t propose to know the answer and I am not slandering people like ‘motoman’ I am sure he knows a hell of a lot more about bikes than I do but I am not sure that these ‘gurus’ know as much about it as they say.
The first discrepancy I noticed with run in techniques was this:
I was working in a bike shop while I was a student and (thanks to an open minded manager) we started comparing demo bikes to ‘new’ sold ones with permission on the dyno when they came in for servicing. And there was a noticeable trend difference with the bikes, the demo bikes almost always had lower power [but only a few % less] in the long run (Over 3000 miles) while the demos almost always had more power in the short run (less than 1800 miles, but more so in 1200 or less).
Now, we knew that the bulk of the ‘new’ bikes were broken in using the factory recommendations while the locals here rode the demos fairly hard, almost exactly as most ‘solid’ run-in methods recommend. Noticing this we started changing the oil much more regularly on the demos and had the staff do a motorman style break in for the first 60 miles (corresponding oil changes). Now, the affect of this was to bring the long run power of the demos back in line with the ‘new’ bikes but the trend power was still lower (smalllll amount). So this seems to suggest that unless you want that power RIGHT NOW! You should just follow the factory recommendations as in the long run (and 3000 miles is not that long at all) you will be better off.
Side note: All demos were run on 98 Premium fuel, customers didn’t fill the demos. As far as I know the customers who owned their bikes also used 98 (98 being the readily available ‘Ultimate unleaded’ in Australia).
It’s a hard call to advocate one method over another. The biggest challenge is to separate out all of the variables to know exactly what is causing problems or delivering benefits.
What I often think is this;
1)1) To remove material from any surface you need to do work on it, in this case this work is friction.
2)2) Frictional work is force x the coefficient of friction x distance.
3)3) Distance would be, say, 1 rpm cycle and force would be proportional to the load on the engine.
Now, depending on the scratch hardness of the materials in your engine the break in process can vary widely in terms of what is actually happening. In terms of frictional work, it makes no difference whatsoever to how fast or hard you run your engine during break in as the above relationship shows that you can develop the same amount of work over time.
What does make a difference (and people brush on this without understanding) is heat. Heat can change the force (due to expansion) and can reduce your scratch hardness. This will have the most impact on surfaces that are most often in contact (rings). Now unless you do a full metallurgical analysis on EVERY part in your engine and happen to know how to make use of this information (and I don’t know how, nor would anyone who is not a metallurgical or a specialized mechanical engineer) you can’t be sure if you want to increase the scratch hardness of your cylinders relative to your rings or not.
Now as to the theory that you can ‘use up’ the roughness of your cylinders, this is complete folly. An easy analogy is that of water wearing through rock. Now… water is not ‘rough’ so you don’t need ‘rough’. It’s all just a matter of time. It is possible that the wear distribution may be effected by un-worn sections coming into contact with a worn cylinder section when you finally let rip. But then I would be inclined to counter that with the statement ‘Its total work that counts’ final equilibrium is dictated by total work, not the work distribution. (I am simplifying here, but it works out this way).
Think of it this way, say you have two drill bits and you want to drill through a thick slab of some tough material. Discounting heat (I have talked about that… say you take your time and use a water cooler) do you really think you would be able to drill through more of the slab if you:
1)Use the 1st bit for half its life (half way blunt), then switched to the 2nd bit for half its life, then back to the 1st until it was blunt and then back to the 2nd till its blunt.
Or
2)Use the first till it was blunt and then used the 2nd till it was blunt.
I’ll tell you now it makes no difference at all. By the way, if you do it at a steady sustainable rate even heat makes no difference as heat will reach its equilibrium within a few mins (or secs) even if you sit there for 5hrs it won’t heat up any more than it did in the first few mins.
So what method am I selling? None… I don’t know what works best in the end of the day but I am pointing out a few of the stupid assumptions that people make such as the ‘use up the roughness’ that motorman proposes. There is probably something else going on in there that he is missing. People often see an effect without knowing the affect.
Based on what I have said above you should probably just stick with the factory recommendations. And before anyone flames me about how ‘x-method gets more power’ well I would probably just say that anyone who follows ‘x-method’ is probably changing their oils more often which is the one thing that EVERYONE agrees on. It’s kind of stupid to me that some people will ride their new bikes 600+ miles before the first oil change.
I should probably leave it at that, I could probably go for a few more pages and seem like an even more pompous ass… In the end of the day I would be inclined to believe the Engineers at the factory… they built the things so I am sure they know more than just about anyone else.
lus1:
