downeyballz Posted November 6, 2008 Report Share Posted November 6, 2008 i have 18cc domes w/ +4 crank ad 65.5 pistons. is it safe to run +4 timing on 93 octane? if thats not safe, will i make more power w/ 20cc domes and +4, or just keep the 18cc domes and ust stock timing? Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted November 7, 2008 Report Share Posted November 7, 2008 youre gonna need to run higher octane fuel anyway it sounds. with an increase in compression or timing its a good idea to run a fuel with higher octane. i wouldnt take any chances with either setup and 93 octane.. if you wanna run 93 octane you better stick to 20cc domes and stock timing. in which case you wont have the power you would have with 18cc domes and +4 timing. Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted November 7, 2008 Report Share Posted November 7, 2008 i have 18cc domes w/ +4 crank ad 65.5 pistons. is it safe to run +4 timing on 93 octane? if thats not safe, will i make more power w/ 20cc domes and +4, or just keep the 18cc domes and ust stock timing? Its going to depend on your porting. You need to check your compression and tell us what it is. More than likely you will need high octane on 18cc domes. Quote Link to comment Share on other sites More sharing options...
downeyballz Posted November 7, 2008 Author Report Share Posted November 7, 2008 im new to 2 strokes. ive always owned 4 strokes. i run 12.5:1 i my yfz on 93 octane w/ no problems. mixing 93 octane & 110 sunoco leaded 50/50, will i be alright with 18cc domes and +4 timing? what makes more power on a 2-stroke, timming or compression? i want the most responsive motor i can get because i do alot of woods riding. Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted November 7, 2008 Report Share Posted November 7, 2008 Its going to depend on your porting. You need to check your compression and tell us what it is. More than likely you will need high octane on 18cc domes. Quote Link to comment Share on other sites More sharing options...
downeyballz Posted November 7, 2008 Author Report Share Posted November 7, 2008 i will cheak my compression this weekend. i would really like to make this engine work w/ pump gas. if i have to i can retard the timing till i get new domes. the porting is also stock Quote Link to comment Share on other sites More sharing options...
firebanshee Posted November 8, 2008 Report Share Posted November 8, 2008 (edited) From my personal experiece you need to at least mix your fuel 50/50 with race gas and 93 octane with anything 20cc and smaller as previously stated, since your motor is bored out to 65.5 this also plays a role.When you increase your bore size it increases the amount of air that you pull into your cylinder thus raising your compression, so with your 18cc dome and your bore i think you need race fuel reguardless of your timing.The more compression you keep in your motor the more torque you will have for your woods riding. Edited November 8, 2008 by firebanshee Quote Link to comment Share on other sites More sharing options...
2001Stroker Posted November 8, 2008 Report Share Posted November 8, 2008 My mods are in my sig, with 185psi, and I'm at sea level. I have to use 110. 1 Quote Link to comment Share on other sites More sharing options...
downeyballz Posted November 8, 2008 Author Report Share Posted November 8, 2008 i dont think a bigger bore will raise the compression, because when the piston is @ tdc its taking up as much space as a smaller piston w/ thicker sleeve. any opinion on what makes more power on pump gas, more compression or more timing, because i cant have both and run pump gas 1 Quote Link to comment Share on other sites More sharing options...
firebanshee Posted November 8, 2008 Report Share Posted November 8, 2008 i dont think a bigger bore will raise the compression, because when the piston is @ tdc its taking up as much space as a smaller piston w/ thicker sleeve. any opinion on what makes more power on pump gas, more compression or more timing, because i cant have both and run pump gas It doesn't have to do with how much space you are taking up as to do with how much air fuel mixture you are compressing into the combustion chamber.Since your motor is bored out to 65.5 it will pull in more air fuel mixture into the cylinder than a bore that is 64mm.So you are shoving a larger volume of air fuel mixture into the combustion chamber that is why when i would choose a dome for a motor that is bored out bigger i start choosing bigger domes to keep my compression were i want it which i usually shoot for about 185ish.If you put a 19cc dome on a motor that is bored 100 over it would be like running a 16cc dome on a 64mm motor. Quote Link to comment Share on other sites More sharing options...
stageIVbanshee Posted November 8, 2008 Report Share Posted November 8, 2008 what mix should i run with 20cc domes and 65.25mm pistons? how much compression should i have? most of the time i do 32:1 and it works pretty good, but i dont know if that is too much oil. i run it on 93 octane is that not high enough octane? i could get 110 but it is $8.00 a gallon at C&C :sad: . the guy i bought my shee from told me to mix it 32:1 and run 93, so i did. Quote Link to comment Share on other sites More sharing options...
downeyballz Posted November 9, 2008 Author Report Share Posted November 9, 2008 what compression / psi, is the highest you can safley run with pump gas? and does the type & ratio of oil used effect the risk of detonation? Quote Link to comment Share on other sites More sharing options...
firebanshee Posted November 11, 2008 Report Share Posted November 11, 2008 what compression / psi, is the highest you can safley run with pump gas? and does the type & ratio of oil used effect the risk of detonation? 165-170 psi , and i am not sure about the oil, i have allways used the same types of oil and the same ratio.I use redline alky mix for my alky bikes and use mobil 1 fully synthetic for my gas bikes at 1 pint to 5 gal. Quote Link to comment Share on other sites More sharing options...
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