8buck Posted June 2, 2006 Report Posted June 2, 2006 (edited) Stock bore/stroke, 18cc domes, +4 timing, 5000ft, 91 octane. I usually mix 110 and 91 50/50 but I can't get any 110 for this weekend, plus, I would like to just not buy it anymore. Edited June 2, 2006 by 8buck Quote
Cotton eyed Joe Posted June 3, 2006 Report Posted June 3, 2006 From my limited experience it sounds like you are boarder line needing to run higher octane gas. I know a few people here that had stock stroke and bore, but 18cc domes and everyone runs +4 ignition. They'd run a mix of 112 (its all the local guy had for a while) and 91 or straight 91 depending, but I don't personally have the knowledge to say you'll be safe. I run about a 20cc dome with all the same shit and I run 91 with no problems so far. Quote
RILS Posted June 3, 2006 Report Posted June 3, 2006 What is your compression?At 5000ft I would say you would be allright with 93 but you should defeitly be fine with 50/50 in my opinion.Im running 18cc at 900ft at 180pounds stock timing and I run straight 111 but i have ran motox bikes at around 170to175psi on 50/50 without problems. Quote
RIPPEN Posted June 3, 2006 Report Posted June 3, 2006 I have stock stroke, dune port, +6 timing and 17cc domes and Iam at 177psi at around 5,000. I run 91/111 which I think is a bout perfect.. Iam guessing with the 18cc you may be around 165-170(a guess) psi so I think you may pushing it with just 91.. Just my .02/ guess RIPPEN Quote
msprouse Posted June 4, 2006 Report Posted June 4, 2006 just buy some octane boost at your local parts store add a couple of cap fulls to each tank and you'll be fine Quote
8buck Posted June 11, 2006 Author Report Posted June 11, 2006 Anymore opinions on this? I really would like to get away with just pump gas (91octane)! Quote
RIPPEN Posted June 12, 2006 Report Posted June 12, 2006 Can you do a comp check?? That way you know right where you are and what you can get away with.. RIPPEN Quote
rocketboy Posted June 12, 2006 Report Posted June 12, 2006 most guys dont thin kabout it but other than igniton and compression your exhaust port height plays a big part in picking a fuel type ,id say run some 100ll aviation fuel and youl l definitly be safe and could even bump the igniton up some . i wouldnt run 91 pump gas in my weedeater Quote
Animalman294 Posted June 12, 2006 Report Posted June 12, 2006 Yes, I agree with the AV 100LL. At 5000 feet you will deffinately be fine with 100 octane, but the 93 stuff would be pushin' it. The Aviation fuel is not as costly as the race gas, but it gets the job done nicely, for a little more than you are payin' for the 93............ :beer: Quote
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