I was hoping some of you banshee fanatics would be able to tell me how much I would need to remove from a stock banshee head to get to around 170 psi. .010, .020? also if I have that much compression, I can still run pump gas, correct?

 

The most you can go with a straight mill is .030 . This will bump a 120compression bike to about 145-150. You cant mill it any more unless you adjust the squish in the dome. If you dont adjust it and mill further it will destroy your engine. As for gas. You can run premium pump to 160, you need mixed from 160-170. then you need straight race gas or detonation will occure. Oh and adjusted timing will lower those numbers a little just for future reference.

Also compression that high isnt good for your bikes crank. I hope you have it welded or it will seperate intime and blow your $hit up, not good. Also I would only increase it a little to get some low end if you increase it to much it will take away from the top end and milling it to much will affect your cooling.

Good luck/

 

thanks for the reply. my crank isn't welded so my next question is, is it ok to mill the head .010 or .020 without the crank welded or am I still asking for problems. thanks again.

 

no your ok. Mines milled .030 over with +4 timing. But thats about as far as I would go for my elevation and still run pump. See at sea level a .030 milled head may produce 160 psi. where as a .030 at 2,000 ft may produce 140psi. You just dont want to much compression or to agressive porting on a unwelded crank. If you live at 3,000 ft you may need to mill your head to about .050 over to get the desired compression you want, but that will require you to adjust the squish. It might be more practicle to get an aftermarket head with interchange able domes.

However if your about sea level you might get the desired compression with a simple mill as I did. Either way I guarentee you will notice a cheep .030 mill. Its a great cheep safe mod.

P.S. Its always a great idea to spend the $80 on your next rebuild to get the crank welded just some cheep insurance and your bottom end will be really strong.