superdad4301 Posted March 6, 2009 Report Posted March 6, 2009 (edited) i have a 7mil longrod twister crank,coolhead,34pwk.run 110,and when it was running it had 192psi on each cyllinder!it has some pitting on one of the domes and it keep blowing orings!i would like to drop the psi to about 180 if possible by changing the dome size!i can't finda size on the domes i have now!any help would be gratful!by the way it is 68mm bigbore cyllinders,stock style,sleeper!thanks shane Edited March 6, 2009 by superdad4301 Quote
shanYE west Posted March 6, 2009 Report Posted March 6, 2009 Where did you buy the domes? they're probably cut from blanks. Quote
superdad4301 Posted March 6, 2009 Author Report Posted March 6, 2009 Where did you buy the domes? they're probably cut from blanks. they were on the bike when i bought it! Quote
superdad4301 Posted March 6, 2009 Author Report Posted March 6, 2009 i was told to try 22cc bigbore domes! Quote
1996dragshee Posted March 6, 2009 Report Posted March 6, 2009 192psi my guess is you have 19cc domes.Call Noss Machine he will hook you up. I just had him cut me some for my 70mm bore,he's very patient and got right back to my phone calls and anwsered all the questions i had.Very nice guy and knows his shit... Quote
shanYE west Posted March 6, 2009 Report Posted March 6, 2009 192psi my guess is you have 19cc domes.Call Noss Machine he will hook you up. I just had him cut me some for my 70mm bore,he's very patient and got right back to my phone calls and anwsered all the questions i had.Very nice guy and knows his shit... I agree.. I'd get ahold of Dave @ NOSS Quote
dajogejr Posted March 6, 2009 Report Posted March 6, 2009 There is a lot of numbers that can account for popping Orings. Squish, squish band, dome stepping, cc volume are a few of the main factors. I run 20cc domes with a generous .050 to .055 squish (ran .055 and .056 in my motor last time, but fresh build, etc.) You'll find tighter squish with a slightly larger band will be fine for short runs (a la 300 foot) but that same dome won't last long on a trail bike or pavement bike that is held WOT for longer than a few seconds. cc those domes if you can, it sounds like it might be too late for a squish test. David Noss will have to know what kind of piston you are using, a banshee type (WSM in a big bore) or a blaster type (Wiseco) The dome angle has everything to do with the shape/crown angle of the piston you're using. Quote
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