bunboy1 Posted March 5, 2008 Report Posted March 5, 2008 hi all, i am doing a compression test and i am just above sea level. i get 150 psi in the left jug and 160 in the right one. is this normal, or do i have an uneven port job? thanks Quote
Bansh-eman Posted March 5, 2008 Report Posted March 5, 2008 it could be a number if differant things causing the differance. normally anything over 10 lbs differance you want to rebuild the motor. Are you doing your test after the bike has had many hours of riding on it , or is this a fresh build and your getting a reading thats 10 off from side to side? Quote
bunboy1 Posted March 5, 2008 Author Report Posted March 5, 2008 (edited) it could be a number if differant things causing the differance. normally anything over 10 lbs differance you want to rebuild the motor. Are you doing your test after the bike has had many hours of riding on it , or is this a fresh build and your getting a reading thats 10 off from side to side? i am doing a fresh rebuild and i am getting 150psi on the left side and 160 psi on the right. my port job was done by ct racing. i am gonna spray some wd40 into the plug holes and do it again. is there anything else i can check? i am also having trouble with my kick starter sticking in the down position, every 10th or 12th kick. why is it doing that? please help, thanks. Edited March 5, 2008 by bunboy1 Quote
Bansh-eman Posted March 5, 2008 Report Posted March 5, 2008 the differance in compression could be that the porting is off but a 10 psi differance isnt something like the guy rounded on of the tranfers a tad more then the other. 10 psi would be a totally differant style of porting so i doubt thats your issue. Your domes could be possibly differant sizes? your squish set the same on both sides? your piston tolerances same? when your doing your test are you wamring the bike up then doing it with the carbs on and throttle wide open until the needle stops moving? Quote
bunboy1 Posted March 6, 2008 Author Report Posted March 6, 2008 the differance in compression could be that the porting is off but a 10 psi differance isnt something like the guy rounded on of the tranfers a tad more then the other. 10 psi would be a totally differant style of porting so i doubt thats your issue. Your domes could be possibly differant sizes? your squish set the same on both sides? your piston tolerances same? when your doing your test are you wamring the bike up then doing it with the carbs on and throttle wide open until the needle stops moving? the domes i got from dave noss are 21cc and are cut for stroker crank. my squish is a little off, i am getting .056 on the left and .057 on the right. i am going to exchange them for another pair, so i can t run them. my carbs are off, because i plan on taking them in to get bored out to 27.5mm. will there be a big difference from a cold compression test versus the hot one, thanks for all your help banshee man. Quote
Bansh-eman Posted March 6, 2008 Report Posted March 6, 2008 (edited) .056 and .057 are fine as far as them not being 100% dead on, but you could tighten the squish up more, ideal is around .040 the differant between hot and cold isnt going to be 20 lbs or anything but thats the correct method to do it. you want the motor to be at operating temps because thats how your going to be riding it. and well all know that metal expands with heat Edited March 6, 2008 by Bansh-eman Quote
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