Originally Posted by
yaegerb
Need to figure out with the volume of your current head is. My guess is its 18CC or below...possibly even 15. I agree with Milner, those are some high numbers you are playing with. I see you are using 110....dunno if that's high enough for the comp's you are running. You need to perform a UCCR to gauge your octane rating. I can tell you my 250R was running like crap about 2 years ago and I performed the UCCR and found my uncorrected compression ratio to be 16:1 and should have been using 116 or higher octane...food for thought. My comp at the time was 218. My head ended up being 15cc's. That was a time bomb waiting to go off. BKM gave me an 89 TRX head to try and solved all my problems. The 89TRX head was stock at 23cc's.
To drop that comp back down you need to get the bowl re chambered, I am only guessing here, but 23-25 CC's should be sufficient.
My dome was engraved with the CC on it but i can't remember what it says. i'll pull it off and take a look.
85 Tri-z Power valve on Inverts
85 Tri-z Basket Case
01 gsxr750 engine/Tri-z frame (long long way from complete)