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I have been reading somewhere that you get good improvements in mid range on a DOHC bike when altering the timing 4° on both inlet (later opening) and exhaust (earlier closing).
The idea is to have (8°) less overlap which cause erratic running at low rpm but is a consequence of the longer duration cams that are found in high power / liter engines.
4° on each cam being still safe with valve to piston clearance.
There was something to do on the ignition timing too but I can't remember it.
Also, if uing the engines only at lower rpm, we could increase the compression ratio wich is a big MPG booster.
On my 250 GN, I plan to boost the CR and polish the chamber and maybe piston crown but unfortunately, being SOHC, I can't play with timing ...
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