Look up camshaft break-in on google. You'll find thousands of results and videos for this procedure. Every manufacturer has one from GM to Honda to Lada. Failure to break the camshaft in properly will result in decreased camshaft life and less lift - either is bad. The higher the valve spring rate, the more critical camshaft break-in becomes although, even a smogger 350 from the late '70's, with no real lift or valve spring pressure, will fail if not broken in correctly.
Point being, when your engine is designed to run to 15,000 RPM (like the bike) then you know the effective valve spring pressure has to be high, really high. The higher the spring pressure, the more critical camshaft break-in becomes, although not limited to that criteria (see smogger example above) it's essential or else your precious lift will decrease very quickly.
This comes back to metallurgy, case hardening techniques etc etc etc. Either way, the majority of camshaft wear will occur on initial start of a new engine, hence the thousands (if not tens of thousands) of articles from various camshaft manufacturers and OE vehicle builders such as GM, Ford, Chrysler et al.
Back in the day (and even today) if you do not break in a camshaft correctly it will likely fail prematurely. In the automotive trade this is very common. I'm sure that modern manufacturing processes reduce the effect (such as billet roller cams) but you will always see the manufacturer proving a very precise break-in procedure that you HAVE to follow on initial engine start. I personally have seen many camshaft failures just on the trade side that were caused by not following the break-in procedure. No kidding, I've seen it first hand probably 10 times or more.
With my last bike I was looking into have custom camshafts made for the market (ie, for sales world-wide). So I researched and spoke directly with camshaft manufacturers for GM, Saab, etc. The mating surface is also very important. In the case of rocker arms, consider this, if your rocker arm is made of steel that is harder then the camshaft - which will wear faster? Even more, which will cause more wear on the other? If you consider this, if you have a harder rocker arm then the camshaft then the rocker arm itself will wear out the camshaft - and quickly. So there is a lot to it. You can be sure that the 'buckets', which are really lifters, on our engine will be manufactured with a very precise hardness that 'matches' or 'mates' to the hardness of the OE camshaft. Typically, the rocker arm or bucket will be a little softer so that they wear (as opposed to the camshaft). After all, you want to maintain the most lift possible and it's easier to change the rocker or bucket.
My guess is that every engine designer/engineer will have their own special recipe for hardness of material between the camshaft and whatever they are using as the rocker or bucket. I doubt anyone will ever find out what the OE recipe is for various manufacturers. When I lashed my valves on the 600 I spec'ed the cams and they were worn at 40k. As I recall, they were close to the OE limit. This can be caused by all sorts of things including low oil or crappy oil. If any or the previous owners did not use synthetic oil then the wear would easily be attributed to that. In my case, I once ran regular motorcycle oil. The engine would use .5 litre in an hour or two. This was a mistake on my part but the point was clear, and I knew this, not running a very good synthetic oil is stupid and causes wear. Only a synthetic can stand up to the shear in induced by the transmission gears or the pressure/temperature between the bucket and the cam at 15,000 RPM.
Sorry about the long-winded reply but most of this is stuff I forgot long ago and it came back to my memory as I thought about this post.
Oh here we go, even more is coming back to me after posting. Because the camshafts and buckets wear in together they 'mate' each other. This is why the OE Honda service manual (or any manual for that matter) will always tell you to keep them together when you strip the engine so that they can go back into the same locations - because they have worn in together. This begs the question, if you want to replace the camshafts do you need to replace anything else? Ask ANY camshaft manufacturer in the world, or an OE company such as GM, and they will always tell you (and in fact insist) that you MUST replace the lifters when you replace the camshaft. This is accurate and it is essential. So in the case of our bikes, if you replace the camshafts you must replace the buckets. This way you have two new surfaces wearing in together as a set. When you do this the majority of the wear will happen in the first 20k which is why Honda says to lash the valves at around that time. Once it's been done it will usually wear less then during the initial 20k as that is where most of the wear occurs - during initial break-in. So if you replace the cams and buckets you will need to re-set the valve clearance during the job and then again at 20k or so. After that, they are broken in, together, as a unit. I would expect longer service intervals after that.
This, of course, begs the question, what about the valve springs? The fact is that as you run around at 15,000 RPM the springs sag. That is to say, the amount of pressure they put on the bucket will decrease. As the pressure decreases the bucket follows less precisely and valve timing gets more slack. Generally this means less RPM, or more precisely, less accurate valve control at higher RPM. So.....if you are replacing your camshafts for some reason, and you are replacing your buckets (for obvious reasons due to camshaft replacement) then it would behoove you to replace the springs at the same time so that you maintain that higher spring pressure that is required to make the bucket follow the cam at higher RPM's.
This is why EVERY camshaft manufacturer will tell you that if your replace the cam you MUST replace the lifters at the same time. If you think about it, you might as well replace the springs. You now have a camshaft with maximum (new) lift and you have buckets with zero wear (again, maximum lift) and yet, pairing that with used springs means increased chances of valvetrain float. That float will damage camshafts and buckets and ultimately reduce your effective lift.
I have experienced this many times when working with one-off camshafts when I was researching different designs for the market. Another place where you can experience this first-hand, and very easily, is with the clutch. When you replace the clutch, replace the springs. Why? Because when they are heat cycled they tend to sag. In my previous business I designed new clutch springs for one particular bike and marketed them world-wide. After designing them I researched the manufacturing process so that I could determine which factory was going to make them for me. The winner was the one that (among other things) heat-cycled the springs and took into account spring sag. So when I ordered up several thousand springs with x rate the springs really did have that rate because when they manufactured them they took into account the sag that occurs during heat-cycling an usage. So if I wanted, let's say, 100 pounds of seat pressure, they manufactured them with, let's say, 110 pounds of seat pressure and then heat-treated them knowing they would loose 10 pounds of pressure due to heat cycling.
At any rate, it's all very simple when you think about the big picture. For max performance, you want maximum designed lift. This means the camshaft must not have excessive wear. Any wear, no matter how small, reduces lift. So wear is the enemy. This brings about the need to break in the camshaft/buckets with the least amount of wear. How do you do that? With really slippery Molybdenum oil. That slippery oil causes the clutch to slip. How do you avoid that? Break the cams and buckets in at higher RPM using that slippery additive. Once done, you replace the engine oil with normal synthetic oil. Why the new springs at the same time? Because they sag over time and will not follow the cam as accurately resulting in less valvetrain control at higher RPM's.
06 CBR 600 RR
Last edited by Arjay67; 02-26-2018 at 09:23 PM.