#21 PostAuthor: Crofty » Fri Sep 16, 2011 1:46 pm
Hi Mikey, basically with a mass produced bike there are tolerances. You get one cam, cam wheel, piston whatever and they all vary slightly. They all will work OK, but to maximise power, fuel economy etc they have to be set up perfectly.
Now take your cams and the two wheels with teeth that bolt onto them, i can guarantee that if you had say half a dozen wheels and you laid them on top of each other and lined the mounting holes up exactly, then not all the teeth would be in the same position. However they are made within a spec that says when you time in the cams using the workshop manual the bike will run OK.
If you look at the engine specs then there will be a bit refering to valve timing, on a Z900 the inlet valve will open 30 degrees before top dead centre and close 70 degrees after tdc. Thats on paper of course, in reality with said mass produced cogs you might find valves opening and closing either side of those settings. By having cam wheels that allow the cam to rotate within and then the bolts tightened it is possible to have the valves open and close exactly hwere they should.
cam chain wear, tensioner wear also allow these settings to slide, that is why some bikes are quick out of the crate, some get worse as you ride them (the wear takes settings further out) and others get better (as the settings begin to improve).
To set them up, you would need to either buy ready modified or aftermarket cam wheels or have yours modified, debbens could do this, when setting up you have to accurately find top dead centre and use a degree disc and dial guage to measure crankshaft rotation and amount of valve lift.
I am in the process of doing this to my Z650 (810 conversion) and have yet to set mine up, but have been reading up on it.
Sorry for the long winded reply, but I think it is something that is often left out and engines that get a different set of cams and they are off the mark and never give the full benefit.
I have pm'd you some useful links about engine tuning, specially cam timing