jesse1004 Posted April 9, 2008 Report Share Posted April 9, 2008 I have a f.a.s.t. head with I believe 20cc domes. stock stroke. I run straight race fuel cuz I have a buddy who bought a whole drum of it and only has one atv. I believe its vp's c12. someone was telling me if I run straight race fuel it can muck up my motor if my compression isnt high enough. Now I know by running to low of octane this can happen but ive never heard the other way around. Is he full of shit? Quote Link to comment Share on other sites More sharing options...
okbeast Posted April 9, 2008 Report Share Posted April 9, 2008 If my muck up you mean mechanically mess it up I don't think so. You're basically just wasting money if you run a higher octane than needed but in your case thats' ok. Quote Link to comment Share on other sites More sharing options...
fox_forma Posted April 9, 2008 Report Share Posted April 9, 2008 whats your compression at? Quote Link to comment Share on other sites More sharing options...
jesse1004 Posted April 9, 2008 Author Report Share Posted April 9, 2008 I dont know what my compression is. Jeff at fast put it together for me and Ive had it for a few months now. Quote Link to comment Share on other sites More sharing options...
letsgetthisdone Posted April 9, 2008 Report Share Posted April 9, 2008 you could prolly go down to 18 or 19cc domes and +4 timing with the c12 depending on your elevation/compression. that'd really wake your bottom end power up.. Quote Link to comment Share on other sites More sharing options...
jesse1004 Posted April 9, 2008 Author Report Share Posted April 9, 2008 you could prolly go down to 18 or 19cc domes and +4 timing with the c12 depending on your elevation/compression. that'd really wake your bottom end power up.. I got the +4 and the dyna ignition. If I go down to 18's would it take from the reliable factor? Quote Link to comment Share on other sites More sharing options...
blanco25 Posted April 9, 2008 Report Share Posted April 9, 2008 you really need to figure out your compression. I ran c12 this last weekend for the first time and my bike ran like shit. So I dumped it and put the normal 100 in it and it ran way better. I threw c12 in it not checking my compression and my bike didn't like it. I heard that if your run that high of octane and dont need it it will hurt you more than help you. Quote Link to comment Share on other sites More sharing options...
letsgetthisdone Posted April 10, 2008 Report Share Posted April 10, 2008 depends what curve your dyna is on... if you're gonna run c12, you might as well go all the way as far as motor setup to run that gas. 175-190psi compression and some timing... Quote Link to comment Share on other sites More sharing options...
dajogejr Posted April 10, 2008 Report Share Posted April 10, 2008 Since Jeff did your motor, I'd ask HIM what to do as far as compression, timing and fuel. More octane won't "Muck" things up...but it is wasted money and perhaps a little wasted performance... You need to find your cranking compression AND compression ratio and go from there. Instead of just putting more compression in it...maybe Jeff's port on this particular motor, or pipe/carb combo doesn't like all that compression or a ton of timing....it's his design, I wouldn't let others just guess what to do with it. You said +4 and the Dyna, does that mean you have a timing plate AND a dyna? You realize that a Dyna advanced the curve 4 degrees over stock on any of the 4 switch settings? Simply put, anytime you take a motor designed to put out 35 HP and double/triple that....things in general won't last as long. That being said, adding compression and timing, if kept in tune right...will last quite a while. Quote Link to comment Share on other sites More sharing options...
jet mech Posted April 12, 2008 Report Share Posted April 12, 2008 I have the same head and domes Jesse and I am sitting at 168psi @1300 ft on cold jugs. The real question you should ask yourself is did you notice a diffrence in performance when you ran the VP as apposed to pump if you did then run it and when you run out of free gas let me know I get avgas at cost at the Lincoln Airport it runs about the same as premium at the pump, and I don't care what anybody says on here; Avgas will never in our life time hurt a fucking carburated gas engine period Quote Link to comment Share on other sites More sharing options...
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