I'm interested in this one, too. I think the CRF's are bucket and shim, just like the YZF's, but with the single cam and rocker arm config instead of a dual overhead cam. The visual I have in my walnut-sized brain for valves tightening up is the valve seats wearing down (or maybe the backside of the valve itself) allowing the end of the valve stem to close, or "tighten", the gap between the bucket and the cam lobe/rocker arm. On the other side, if getting looser, I envision the shim and/or the bucket and/or the cam lobe wearing down ever so slightly, opening the gap a bit.
Here's one that always puzzled me: Let's say the valves are just outside of proper adjustment-one direction or the other, doesn't matter for this hypothetical scenerio. The difference is so minimal in comparison to how far the valve travels when it is in full open position, as long as the valve seats fully, ie: not so tight that the stem/shim/bucket is resting on the backside of the cam lobe/rocker arm that the valve is not held into the seat with the full force of the spring, how could this effect starting the way it does? I've gotten pretty good at thinking "you're valves culd be too tight" when I read about hard starting issues, but realize I don't understand why "tight valves" would cause this hard starting situation (I've fallen victim to parroting something, even if just to myself, that I've read enough times to have commited it to memory). Seems to me that the only two real issues here are that the cam lobe doesn't "slap" the bucket if OOS loose, or that there isn't constant pressure on the lobe if OOS tight (ie: Loss of compression due to a valve not fully seated). Am I correct, or is there some aspect of 4smoke design theory involved here that I'm not aware of?
Rich? Bill? Any other 4t professors out there?
ps: Sorry for jumping onto your thread, Bryan! ;)