shrimp Posted March 17, 2010 Report Share Posted March 17, 2010 i have an 06 421 cheetah cub 35 carbs 20 domes on super pump gas. that runs fine while breaking it in. the first time i get on it it blows the left oring. the bike has been sitting for a year. it blew the oring then the top of the piston broke. anybody have any idears? Quote Link to comment Share on other sites More sharing options...
broncbob Posted March 17, 2010 Report Share Posted March 17, 2010 O ring on the head?? Quote Link to comment Share on other sites More sharing options...
firebanshee Posted March 17, 2010 Report Share Posted March 17, 2010 i have an 06 421 cheetah cub 35 carbs 20 domes on super pump gas. that runs fine while breaking it in. the first time i get on it it blows the left oring. the bike has been sitting for a year. it blew the oring then the top of the piston broke. anybody have any idears? You are running to high of compression for the fuel you are using, i pump about 185 at sea level with a 21cc dome on my 421. Quote Link to comment Share on other sites More sharing options...
firebanshee Posted March 17, 2010 Report Share Posted March 17, 2010 Is it a trinity dome? Quote Link to comment Share on other sites More sharing options...
shrimp Posted March 17, 2010 Author Report Share Posted March 17, 2010 Is it a trinity dome? no its a noss head Quote Link to comment Share on other sites More sharing options...
shrimp Posted March 17, 2010 Author Report Share Posted March 17, 2010 O ring on the head?? yes on the head Quote Link to comment Share on other sites More sharing options...
shrimp Posted March 17, 2010 Author Report Share Posted March 17, 2010 You are running to high of compression for the fuel you are using, i pump about 185 at sea level with a 21cc dome on my 421. i have no idear what im running. never checked the compression. Quote Link to comment Share on other sites More sharing options...
shrimp Posted March 17, 2010 Author Report Share Posted March 17, 2010 no its a noss head sorry its a f.a.s.t dome Quote Link to comment Share on other sites More sharing options...
broncbob Posted March 17, 2010 Report Share Posted March 17, 2010 You might have just got it installed wrong? Now on the the piston, what elevation you at? Do you have a compression numbers that it was before the piston broke? Quote Link to comment Share on other sites More sharing options...
shrimp Posted March 17, 2010 Author Report Share Posted March 17, 2010 You might have just got it installed wrong? Now on the the piston, what elevation you at? Do you have a compression numbers that it was before the piston broke? sea level and i did not check the compression. it was built from a shop twice. Quote Link to comment Share on other sites More sharing options...
shrimp Posted March 17, 2010 Author Report Share Posted March 17, 2010 You are running to high of compression for the fuel you are using, i pump about 185 at sea level with a 21cc dome on my 421. should i try 21's? i cant find anyone around here that knows about a cheetah cub. Quote Link to comment Share on other sites More sharing options...
broncbob Posted March 17, 2010 Report Share Posted March 17, 2010 I'd give Herr Jugs a call and get some help from him. He can give you a idea what domes you need to run, and can get you the parts as well. Great guy to deal with as well! Quote Link to comment Share on other sites More sharing options...
firebanshee Posted March 17, 2010 Report Share Posted March 17, 2010 should i try 21's? i cant find anyone around here that knows about a cheetah cub. What fuel and octane are you going to run? If you run a 21cc dome you will have around 185 on the compression at sea level that would require staight race fuel. If you are going to run pump gas then you would have to run around a 24cc dome. Since you have a 68mil bore that is a big bore so you are compressing more air, so a 21cc dome on a stock cylinder bore will have a lot less compression than a 68 mil bore. So what octane of fuel are you going to run? Quote Link to comment Share on other sites More sharing options...
dlnoss Posted March 17, 2010 Report Share Posted March 17, 2010 Yea, what the other guys are saying. I wouldn't recommend 20cc domes on a stock motor at sea level on pump gas. Detonation will lift the domes and blow the oring. When you put it back together, run larger domes or higher octane (or both). -David Quote Link to comment Share on other sites More sharing options...
shrimp Posted March 17, 2010 Author Report Share Posted March 17, 2010 What fuel and octane are you going to run? If you run a 21cc dome you will have around 185 on the compression at sea level that would require staight race fuel. If you are going to run pump gas then you would have to run around a 24cc dome. Since you have a 68mil bore that is a big bore so you are compressing more air, so a 21cc dome on a stock cylinder bore will have a lot less compression than a 68 mil bore. So what octane of fuel are you going to run? 93 pump gas Quote Link to comment Share on other sites More sharing options...
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