440ex Top Speed/race fuel

[walsh440]

i have 12.5:1 piston, stage 2 jets, rev box, open air box, stage 2 cam, I was running vp c12 which is 108 octane, running that 50/50 with 89 pump. then i jumped it up a step, ran 70% race, 30% pump, and seem to do ok, then took it trail riding, and was acting up alittle.... Do u think if its best to run staright race fuel or mix it, because either way top end is just alittle weird, doens't seem to be there, i'm going to jump front sprocket up 16 teeth, and maybe drop the rear 1 or 2, but i wanna try to get this straighted out first.....what am i doing wrong? I mean the torque in this is awsome, I was thinking of running staright 103 octane and seeing how that worked, but i figured i try to get some info from u people out there...Thanks in advance for the help

[duneittilludie]

walsh440-I was just riding today with a friend of mine who has a 440ex with the same compression as you and a similar set up for everything else and he has found that straight 110 octane works best for him.

[walsh440]

ok thanks alot, that's pretty pricey just to run straight face fuel, but u wanna play u gotta pay right? haha

[duneittilludie]

walsh440-With 12.5:1 compression you will probably have to run pretty close to the same octane level as my friend does.Your comment about the top end not performing well may be in the jetting that you have and in fact it sounds like you may be rich so you may want to step down on youre main jet size to see if that cures the problem but dont go too far from where you are at now without checking the plug.

[420EX]

right now im running a CT built 13.5:1 motor on 100 octane race fuel which costs $3.75 a gallon at gas city, i should be running 110 but I cant find it anywhere, where do I get 110 octane? my advice to you would be to run at least 100 octane with the 12.5:1 piston.

[walsh440]

check out vp racefuels.com, I get my race fuel from Honda here in harrisburg pa.

[walsh440]

duneittlludie,
Right now my plug is buring great, so u think i shoudl go down a step in the jetting? i'm running a dj170 right now, and that's below 3,000 feet with after market exhaust, the next step down is with a stock exhaust, ?!? help me out, lol, thanks alot

[cals400ex]

i would try going down a size or two on the main unless you think you will be too lean. however, i don't think you should be.

[devilstalin]

Originally posted by: 420EX
right now im running a CT built 13.5:1 motor on 100 octane race fuel which costs $3.75 a gallon at gas city, i should be running 110 but I cant find it anywhere, where do I get 110 octane? my advice to you would be to run at least 100 octane with the 12.5:1 piston.

i know they sell octane booster. however i dont know how well it works

[radfastdude7777777]

i would try a bunch of different jets thats how my friends 250ex works so good now