Bansheeman1121 Posted July 30, 2006 Report Posted July 30, 2006 Whats up guys gave up on the shee a while ago after putting lots more money into it and having it f### me yet again, but just for the hell of it wonderin what compressoin numbers should look like with a mid -top end port and 20cc domes, i got 120 psi in each with a brand new top on which looks good maybe a little more wear than it should for the 10 min of run time it had but cylinders and pistons still look new so what should my numbers be round 800 ft Quote
broke Posted July 30, 2006 Report Posted July 30, 2006 It's hard to say for sure, but raising the exhaust port will definately lower you compression numbers. Quote
BigRed350x Posted July 30, 2006 Report Posted July 30, 2006 It's hard to say for sure, but raising the exhaust port will definately lower you compression numbers. I agree, porting will drop compression. I would think with 20cc domes you should be higher than 120. even with porting. Did you check cylinder/wall clearances and ring end gap and ring toleraces before you put it in or did you just slap some new stuff in there and expect everything to be hunky-dory? Quote
Snopczynski Posted July 30, 2006 Report Posted July 30, 2006 I agree, porting will drop compression. I would think with 20cc domes you should be higher than 120. even with porting. Did you check cylinder/wall clearances and ring end gap and ring toleraces before you put it in or did you just slap some new stuff in there and expect everything to be hunky-dory? Bore size will lower the compression also. Stock bore with a port job will probably be in the 160-170 range. Quote
jbooker82 Posted July 30, 2006 Report Posted July 30, 2006 What kind of compression gauge are you using. If it is a cheap on that has the long threaded adaptor that screws on to the hose take a look at this. This is what I have found. Compression Tester Thread LINK Quote
rocketboy Posted July 30, 2006 Report Posted July 30, 2006 (edited) i ported the engine ,the clearances are fine ,the bore is fine . the exhaust port timing is still conservative ,id guess around 145 lbs with 20cc domes would be close @ 800 feet . if yo u need help give me a call or a pm me ..dont give up yet everything is fixable Edited July 30, 2006 by rocketboy Quote
BigRed350x Posted July 30, 2006 Report Posted July 30, 2006 i ported the engine ,the clearances are fine ,the bore is fine . the exhaust port timing is still conservative ,id guess around 145 lbs with 20cc domes would be close @ 800 feet . if yo u need help give me a call or a pm me ..dont give up yet everything is fixable That's always cool when you can get the guy who did the work to chime in and help you out. :beer: Quote
rocketboy Posted July 30, 2006 Report Posted July 30, 2006 That's always cool when you can get the guy who did the work to chime in and help you out. :beer: yeah i wanna see his bike rip like i know it can , call me and we can try to diagnose the problem .dont give up on it or listen to that dummy mechanic Quote
racer Posted August 1, 2006 Report Posted August 1, 2006 Bore size will lower the compression also. Stock bore with a port job will probably be in the 160-170 range. how do you figure? more surface area (bore) to push more air into the same confined space. i think it goes the other way. Quote
RATBIKE0130 Posted August 1, 2006 Report Posted August 1, 2006 Boring a cylinder larger without adjusting the head/domes will increase static and running compression numbers. A ported motor will show lower compression numbers when kicking the motor but once running the numbers will increase if everything is working together properly. Your gauge may read 120psi but, who's to say that the gauge you used is accurate? Quote
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