Figured I may as well introduce some of the planned engine mods (at this stage - can always change). So far no plans to do much with the bottom end, it'll all be improving gas flow, capacity and compression.
_ Custom made high comp 77mm piston (263cc, retains stock sleeve, no case boring required) - piston already measured up and sent to Special Piston Services in Australia - they specialise in one offs and a re super friendly with a lot of experience: http://www.specialpistonservices.com will try raise cr from 8.9:1 to 9.5:1 or even 10:1 if we can work out a good dome.
_ Hot cam, the most aggressive profile, regrind by Tighecams in Australia: http://tighecams.com.au
_ Ported head to allow better airflow - or, to allow the cam to do its thing
_ Custom titanium intake valve, SS exhaust valve, both with narrower stems and both much lighter than stock - will maintain same valve size though (more on that later)
_ Valve seats custom made from NBC to wick away heat from the ti valve better
_ Bronze valve guides - also for better heat transfer to the head
_ Single beehive valve springs
_ Titanium keepers, seats and retainers
_ Lightened rockers and tappets
Then I'll be doing a few things on the intake and exhaust side too - as mentioned previously some kind of crank case ventilation scavenging system and probably a harmonic intake.
As an experiment, I already tried lightening some rockers I had from a spare engine. Good and worth while result. Especially becuase the weight shaved is at the points furthest from the fulcrum - where they 'weigh' the most to the valve train. Those small tabs at the end of the rocker are for the decomp lever on the XT and TT model engines and because the rocker is a symmetrical part, Yamaha have used it on the intake side as well - where it is not needed (where neither are needed in the case of the electric start SR). I will be converting to kick yes, but am hoping with the right technique, won't need the decomp set up from the XT engine.
Hoping to lift the rpm ceiling to 10,000 by putting the whole valve train on a diet with the aforementioned mods ;D