Oldfeller2 wrote on 01/19/08 at 22:24:41:Shaving the head moves your cam gear down towards the crankshaft. What will amaze you is that the head shave amount hits cam chain "slack factor" with a 2x multiplier and it, by itself, could take out most of your chain adjustment service life.
Horsepower is an elusive animal, more is nice but at what cost?
Check into nitrous if you want low cost serous hp -- low cost until you start seeing what nitrous stresses will do to your clutch and transmission that is.
I’ve been using nitrous on bikes and cars for 20 years and I’m yet to see any damage to clutch or transmission as a result – nitrous has an unfair reputation for damaging things which isn’t deserved at all. Like anything else, you have to use it sensibly. If you add a LOT of nitrous, only a fool leaves his clutch standard!
Several hundred pounds for a nitrous system isn’t cheap for a little extra torque compared with £20 to skim the head. That aside, I don’t want to nitrous this bike – I could put some spare solenoids on it if I wanted to, but I just want a bit more grunt for normal daily use.
I just want the engine to run a little more efficiently, so I’ve ported the head, I’m using free flow air filter, modding the carb and I’m going to skim the head. I looked at the possibility of welding up the combustion chamber, but that’s not an option of a 4-valve pent roof.
I’m aware that, as with all engines with chain driven overhead cams, there will be an effect on the cam chain and timing – easy answer to the timing is to modify the cam gearwheel so the cam timing can be dialled in. As for the extra slack in the chain – that’s manageable.
Now, back to the question – can anybody answer how much material can come off the head before the pistons need pocketing for valve clearance?