Jbeck103 Posted December 10, 2012 Report Share Posted December 10, 2012 Trying to decide what size domes to order for my quad. As far as I know my crank is completely stock and dont know what compression they will hold up to? I wanted to go 20cc but dont want to if I have to remove the crank. Any comments would be greatly appreciated! Also what is stock head cc??? Quote Link to comment Share on other sites More sharing options...
fat_tony Posted December 10, 2012 Report Share Posted December 10, 2012 stock is 24 i think....i put 19 in mine but i figure ill need race gas or at least a mix when temps get back over 70 but everything i read said 21 is safe minimum for pump gas.....too many factors involved to say whats safe for your situation but i thought id share my 2 cents lol Quote Link to comment Share on other sites More sharing options...
Finch Posted December 10, 2012 Report Share Posted December 10, 2012 no matter what if your altering any power you should weld the crank. even a bone stock bike a crank can let go Quote Link to comment Share on other sites More sharing options...
Burt Reynolds Posted December 11, 2012 Report Share Posted December 11, 2012 stock is 24 i think....i put 19 in mine but i figure ill need race gas or at least a mix when temps get back over 70 but everything i read said 21 is safe minimum for pump gas.....too many factors involved to say whats safe for your situation but i thought id share my 2 cents lol Im pretty sure as it gets warmer you will need less octane. Cold air is more dense Quote Link to comment Share on other sites More sharing options...
spurdy Posted December 11, 2012 Report Share Posted December 11, 2012 I agree with finch on welding the crank. If it comes out of phase or spreads you can ruin a set of cases or worse. As far as compression, I think you'd be fine with 21 cc domes depending on elevation. But as said, many factors should be considered. SP Quote Link to comment Share on other sites More sharing options...
fat_tony Posted December 12, 2012 Report Share Posted December 12, 2012 Im pretty sure as it gets warmer you will need less octane. Cold air is more dense yes cold air is more dense but octane is a rating for resistance to pre ignition based on combustion chamber temps before spark happens....like when u compress air it heats up ..... so i mentioned the octane because when its hotter than Hades the chance for preignition goes up alot because the entire motor and even the intake air is hotter so i might need either lower compression or higher octane ....but i could be all wet hell i don't know lol maybe somebody smarter than me can explain it better . Quote Link to comment Share on other sites More sharing options...
Jbeck103 Posted December 13, 2012 Author Report Share Posted December 13, 2012 Running a higher onctane is not a big deal to me at all. The crankshaft if the only thing I am worried about with deciding dome sizes. I am at 900ft altitude Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted December 14, 2012 Report Share Posted December 14, 2012 I also recommend welding the crank before you increase compression. What year is the bike? It is probably do to be re-sealed anyhow. Send the crank off while it's apart. CC size will depend on a few factors. Portwork? Elevation and fuel to be run. -Brandon Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted December 14, 2012 Report Share Posted December 14, 2012 Im pretty sure as it gets warmer you will need less octane. Cold air is more dense Correct....the colder it is the more dense air becomes. The more dense it is means there are more air molecules in a specific area of volume at say 32*F than there is at 80*F. This means that the more dense air is.....the more fuel you need to run. Amount of fuel.....not octane. That's why we advise changing jets when the weather changes drastically. Don't get me wrong.....octane and air temp do play in with each other......but barely. Quote Link to comment Share on other sites More sharing options...
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