Engine breakin. The topic that can raise more religious fervor than the question of how many angels can dance on the head of a pin. I can only think of one topic that raises more hackles and I'm not going to mention it now as it would get the tempers heated up so high that no one would read the message below. And I typed for too long to let THAT happen...
This past weekend I had dinner with a buddy of mine that has been playing with the innards of motorcycles and working as a professional engine rebuilder for more years than many of you on the board have been alive. He's the type of fellow that has a true and keen intrest in engines of ALL sizes and has worked on them all from the smallest model airplane engines up to earth mover engines with pistons the size of paint buckets. His specialty is cylinder grinding and prep for assembly. He's also a motorcycle rider that isn't beyond the practice of taking apart a bike just out of curiousity to see what's happening inside. He would definetley be a category 1 in my "Who does their own work?" poll thread.
I asked him about breakin procedures. How long they should be and the dangers of too fast a breakin and too LOOOOOONG and mild a breakin. Here's what came out of it.
Modern engines use a honeing procedure uses a set of steps that results in what is called PLATEAU honing. Basically there are grooves in the wall with flat polished tops for the rings to ride on. In the distant past the honing was left with relatively sharp tops on the hone marks and it took some time for the rings to wear these down to the plateau shaped that is done more or less first time around with the new hones. This has reduced the effects of and need for a breakin by an order of magnitude compared to a few decades back.
As for the rings they used to be made with a ground flat outer rim. Studies of the rings in engines that had been properley broken in showed that there is some rocking flex in the rings as they move up and down that resulted in the broken in rings showing a subtle curve or barrel shape on the contact faces. Modern rings are premade with this curve already formed on the rings.
All this has greatly reduced the breakin requirements in engines produced or rebuilt in the past decade or more. BUT..... Nothing in perfect and there is always that little bit of benificial scuffing in to a final shape that can come from a proper breakin. The honing of the plateaus is good but because of the tool used it does not leave a perfectly cylindrical wall. Small local micro waves and micro burrs are formed that will wear away during breakin. And while the rings are good enough that they seal with pressure all round their periphery there "MAY" (I had to fight this admission out of him ) be some minor pressure variations that will even up with a bit of breakin. He also said that the roughness between the walls and rings is so slight that it will wear away very quickly whether you use it to form a final seal or not. This is important and forms a lot of the logic behind the accelerated breakin procedure that is found in a few places on the 'net.
So, what DOES a good breakin consist of? We'll get to that in a moment but first a key definitions and urban myths that were discussed .....
We all know that lugging the engine is bad for it. But I've heard as many definitions of lugging as there are motorcycle riders and car drivers. Basically lugging is using the engine hard and with more than 1/2 throttle where the road conditions prevent the RPM's from climbing above 1/4 to 1/3 of the maximum redline. For example when you insist on climbing Royal Oak hill in 4th or 5th gear. Pottering along behind Ma and Pa Kettle in stop and go traffic while barely cracking the throttle in first or second is NOT lugging the engine. Similarly cruising at 80 on a flat road at 1/3 the peak RPM is not lugging the engine. Bragging about doing the Loop in top gear the whole way IS lugging it in many spots unless you hit the base of the hills at redline....
Lugging an engine like ours is bad at any time but particularly during breakin.
Doing so restricts the amount of oil splash. And any wet sump engine depends on oil splash for lubing some of the key components. Central in this list is the top ends of the con rods and the lower cylinder walls. When lugging the engine torque is very high and the load is on the parts for a comparatively longer time. This tends to squeeze out the oil from the top end bushing and may lead to metal to metal contact. A very bad thing in a bush type bearing. Similarly the cylinder walls depend on the splash oiling to lube them. When the piston is at TDC the lower walls are exposed to splashes of oil that lube and cool these surfaces. The residual oil is mostly scraped off by the oil control rings but a small part stays behind to lube the compression rings. Remember the valleys in the PLATEAU honing? The valleys hold "just" enough oil to lube the rings without lowering the oil level too fast. ALL engines consume oil but if they are in good shape it's only about a cup over the change interval. The cylinder wall grooves is where it goes mostly. A little extra leaks down past the valve seals through the engine.
Glazing or glazed cylinder walls-
It's not easy to do but if you run your new engine at too light a load for too long the rings and peaks of the walls will not cut each other away to form a nice long lasting sealing surface but will tend to polish (perhaps a form of work hardening?... he didn't say that, I just thought of it) to what is known as a "Glazed" wall. Once glazed the engine will tend to burn more oil and have more blow by. Blow by gases means that some gas has escaped from the combustion chambers and this tends to lower the chamber pressure which is what does the work during the power stroke. So a glazed cylinder will not produce as much power as a properley sealed one. It's not much but it's there.
You've all heard that you should not use sythetic too soon. Why's that? My buddy noted that the film strength of these oils is SO good that they don't get scraped away by the oil control rings properly until they are broken in and can shear off the film a bit better. Using this oil too soon means that a film is left behind as the rings "aquaplane" over the oil and that oil film is exposed to the combustion chamber gasses that strips it off the walls. So your engine not only won't breakin the rings properley but it'll tend to use more oil. Oddly enough he said there should be no side effects other than the engine will tend to use oil and that oil may foul the plugs more often. The synthetic being SO tough that it doesn't burn in the combustion fires as dead dino oil does.
Do NOT run a new bike at a constant speed- Urban Myth #2-
As long as you avoid the lugging aspect described above there is nothing damaging or habit forming about running an engine at a constant speed. I think the real problem is that it implies that you're running for too long with a light load on the rings that can possibly contribute to a polishing action rather than a cutting action at the ring to wall junction and thus glaze the piston rings or cylinder walls as described above. The often heard claim that you'll produce a "one speed only" engine is hogwash.
Finally he mentioned that he had heard from one rep that many companies "run" the engines to test for proper assembly and fit by connecting compressed air to the spark plug holes and immediatley spin up the engine to a fairly high RPM to look for problems. The pressures needed to do this means that the rings are partially broken in during this test. While he could not completley deny the idea he was quite certain that they do not run them on gas before putting them into the bikes. At least in Japan anyway.
SO... let's get to the talk of breakin procedures and myths....
How fast is TOO fast? He said that if you go up to your brand new bike, start it up and snap the throttle open so it rockets up close to redline you will rip off the little burrs and peaks of the honing and the rest of the breakin will be compromised or at least delayed. And also he suggested that if you start it up rocket away hitting redline in every gear as soon as it's warm that may or may not produce similar damage. Avoid these two scenarios and you probably won't hurt it. Pretty extreme to be sure.
On the other hand when I described what I remember of the usual manual description for a "proper" breakin he suggested that it was so slow and long that it could easily produce a glazed cylinder wall that would never breakin fully or at least delay a decent breakin to a very late date. We both agreed that it was there to try to avoid the guys that would hop on and ride them like in the previous paragraph for the most part. He also suggested that if the new owner took the manual to heart and didn't even approach the restricted limits that it could easily lead to wear in bad spots thanks to not producing the amount of oil splash that would be needed to help breakin the new engine.
Now we can get to the meat of the matter. When I described the accelerated breakin procedure seen in a few spots in the net and around here he was actually in full agreement that it would produce a fast and proper breakin in a short time and quite possibly a superior engine. He also said it was next to impossible to damage anything in using the magic 1 hour breakin. For those that don't know about it this is the method that sees you riding mildly for the first 10 mintues, moderatley hard for another 10 minutes and then a few "drag strip" runs through the first 3 gears using 2/3 throttle and 2/3 peak RPM for a few runs, 3/4 throttle and RPM for a few more and then a series of full throttle and redline runs to finish. The drag strip runs are interrupted by frequent and random roll offs at higher RPM's to allow the cylinder vacumn to draw oil up past the rings and onto the walls to cool and lubricate the breakin wear. This being the reverse of the usual blowby action. This whole breakin procedure from first start of the new bike to finished taking about an hour. Return home for new oil and filter and you're done. Ride it without a care from there but follow the rest of the short time oil changes and services so that other factors can be monitored.
If you just can't bring yourself to do it this fast then stretch it out over the first 500 to 600 kms instead. He suggested that it would not be quite as good but is certainly bound to produce a "tighter" and better sealed engine than the procedure layed out in the manual.
I asked him about heat cycling the engine to relieve some forging or casting stresses that would result in minor shape changes and he said it just wasn't an issue with the modern parts found in our engines. So much for THAT myth. This was one aspect that I was sure had a real effect. Well ya learn something new every day.... even at MY age...
He claimed that he would have no qualms about using either method. Which one would produce the "best" engine? He said the first one, but only a dyno MAY see the difference depending on various factors.
We talked about why the manufactures stick to this slow and painful breakin that they describe. He suggested that it might be due to the fact that no one would follow it but they may tend to hold back a little just because they are worried about it in the back of their minds. Another possibility is that if you think to go slow so the engine can break in properley you won't be slipping on the tire coating in the first 100 kms or so.
All this talk reminded him of the breakin procedure for his first new bike. It was a 1965 Yamaha RDsomethingorother305. The book said "Do not use full throttle for the first 100 miles". That was it. Nice and simple.
To sum it all up I'd like to quote what Trevor at BK told me when I picked up my 98 9R.... "Just USE it but don't AB-use it. Don't bother with the book breakin". I did it that way on my 98 and it was a honkin' strong engine. When I got my 2000 9R I didn't have the luxary of any OPEN country rides for the first 600 or so kms due to various circumstances. I noticed that the 2000 model took a long time to get to where I thought it matched the 98 for power. I'm quite sure it was due to that grandmotherly first 5 or 600 kms that I was forced into. Next time around that I have a new bike I WILL be using a very close copy of the fast breakin method.
I found this talk informative enough that It'll probably be copied to the Articles section. Any truly informed pro or counter opinions will be attached.
LET THE FLAMES BEGIN ! ! ! ! !