vainavic Posted March 27, 2007 Report Share Posted March 27, 2007 I have a 421cc cheetah, lighten flywheel, 34mm pj carbs, taller gears in the tranny(rz 350), clutch, pipes etc, I have my timing at zero, I have an adjustable timing plate should I advance it, What would it help, and what would it change. Jetting? thanks jeff Quote Link to comment Share on other sites More sharing options...
cam2 Posted March 27, 2007 Report Share Posted March 27, 2007 I have a 421cc cheetah, lighten flywheel, 34mm pj carbs, taller gears in the tranny(rz 350), clutch, pipes etc, I have my timing at zero, I have an adjustable timing plate should I advance it, What would it help, and what would it change. Jetting? thanks jeff what is your compression? what size domes? what octane fuel are you using? you have to take these things into consideration while advancing your timing. if you're running a low octane fuel with high compression and you start advancing you timing then you'll get detonation, which is a bad thing. people will be able to help you easier with some more info. Quote Link to comment Share on other sites More sharing options...
vainavic Posted March 27, 2007 Author Report Share Posted March 27, 2007 compression is 145psi, domes are 19cc, using 96 octane fuel Quote Link to comment Share on other sites More sharing options...
Trick2stroke Posted March 27, 2007 Report Share Posted March 27, 2007 What elevation are you at? That seems like low compression for 19cc domes. at 145 lbs and 96 octane you should be fine advancing your timing around 4 deg. atleast. I'm no expert though. Quote Link to comment Share on other sites More sharing options...
cam2 Posted March 27, 2007 Report Share Posted March 27, 2007 compression is 145psi, domes are 19cc, using 96 octane fuel it seems to me with 145psi that you could get away with a +4 advance. if you have a chance ride the bike a little bit to warm it up and get a feel for how it runs in a certain area then advance the timing and see how it runs in the same area. listen to the engine to make sure it doesn't make any odd noises or vibrates any more than normal after you advance and if it runs worse back off the timing. you may have to bump up the octane to 100 if you notice any issues, but i've ran higher compression than 145 with +4 and sometimes +6 on 100 octane without any issues. keep in mind that every bike will run a little different with similar mods. Quote Link to comment Share on other sites More sharing options...
cam2 Posted March 27, 2007 Report Share Posted March 27, 2007 What elevation are you at? That seems like low compression for 19cc domes. at 145 lbs and 96 octane you should be fine advancing your timing around 4 deg. atleast. I'm no expert though. i think the reason that his compression seems low with 19cc domes is because he's up north. Quote Link to comment Share on other sites More sharing options...
vainavic Posted March 27, 2007 Author Report Share Posted March 27, 2007 compression is 145psi, domes are 19cc, using 96 octane fuel I miss typed I have 22cc domes I think I 1000ft above sea level in michigan, right? Quote Link to comment Share on other sites More sharing options...
dajogejr Posted March 27, 2007 Report Share Posted March 27, 2007 I miss typed I have 22cc domes I think I 1000ft above sea level in michigan, right? There is no where in MI above 1000 feet. Average is 500 to 1000....even at Silver Lake. 145PSI with 22 cc domes is AWESOME. I'd go +4...just keep an eye on your spark plugs and listen to your motor....should be ok with 96, might have to bump it to 100. Quote Link to comment Share on other sites More sharing options...
cam2 Posted March 28, 2007 Report Share Posted March 28, 2007 in case you're interested in finding what your elevation is. here is a link to the subject that is pinned in the general discussion forum. http://www.bansheehq.com/forums/index.php?showtopic=71029 Quote Link to comment Share on other sites More sharing options...
jankab Posted March 28, 2007 Report Share Posted March 28, 2007 I have a 421cc cheetah, lighten flywheel, 34mm pj carbs, taller gears in the tranny(rz 350), clutch, pipes etc, I have my timing at zero, I have an adjustable timing plate should I advance it, What would it help, and what would it change. Jetting? thanks jeff Give her +7 degrees, you might have to switch to race gas, but it would be worth it Quote Link to comment Share on other sites More sharing options...
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