13.1 will help a little but if your gonna run race gas and want bottom end you should have gone a touch higher. I think they offer a 13.6ish and that would have been better. You will probably pick up about .5whp across the board with the piston you got. What other mods have you done? If you milled your head a touch you could get up around 14.1 and that would probably work much better at picking up good bottom end. 13.1 is just not enough to notice.
13:1 is the highest i could find through my dealer. I put a 12.5-1 in my yfz450 and i noticed a fairly big difference in low end power. I got the motor together tonight and i am hoping to get on it tommorow
Yea I ordered it through the dealer because it was about 80 bucks cheaper then the rossier piston. I am almost wondering if it was a mistake because this thing runs like a dog!! It revs fine and doesnt sound abnormal but it just has no power.
I told you, you wouldnt notice anything. 13.1 pistons are a waste of money. If you are gonna have to run race gas might as well go higher. Then actually feel a difference. 4 strokes love high compression.
i havent had it dyno-tuned. I think thats gonna be the next step. I didnt want to run higher then 13-1. I know my yfz runs awesome with 13-1 in it. I have a friend who ran 13.5-1 in his and he liked it better with stock in it. They tend to rev better with lower compression. Hopefully i can get this tuned in.
I have the motoworks pipe, airbox lid removed, 13-1 piston, pink wire cut and stage 1 ECU. Does anyone have any recommendations as far as an efi controller goes?
What you are running up against here is two things: Compression equals added resistance. Another thing is, race fuel burns rich. Rich will give you a lazy feel, and coupled with the added resistance of the high compression piston you are probably making less power overall than stock. You will have to get a fuel programmer or reflash your ecu and at least do an exhaust cam swap to pick up the gains the piston will give you. Add a good head port and a full exhaust,with a sniffer tune on the dyno and hold on.
right now i have a k&n, fmf programer, and a woods pipe. i was told the higher in elavation the higher in compression i could go ?? can you feel the defference on 12.5 over stock. what do you have? thanks