top end knock

[Unstock240]

I know that my blaster has the typical top end rattle. It seems that when I run for about 30 mins it gets a bit louder. The thing is all the top end clearances check within spec, and a bearing or something usually would always be loud. My compression is about 140. I think it might be running low octane possibly? Would maybe running premium help?

 

[daniel3877]

when i first got mine i use to try and run low octane fuel ,cause at that time it was stock. but it would ping and detonate terrible. after a few rides i switched to good oil, amsoil, klotz etc and ran sunoco 93 and havent heard anything bad again. runs great. i would absolutely switch your fuel. I bet thats your problem

 

[mr_3_0_5]

lol.. i have to run sonoco 110 mixed with a little 93 and klotz if not i get knocking bad..

 

[stephen12091985]

i ran mine with 93 all the time and mixed with maxima and mine still knocked then my piston broke.my friends blaster didnt have any kind of knock at all when he had it before it was stolen

 

[2smoker85]

mine never knocks i run 34:1 with yama 2r

 

[daniel3877]

i dont have a big bore kit in mine, just port/polish with head milling , and 93 works just fine. mr305, you have a big bore kit and head work done, and thats why you have to run that fuel, if you ran that in a stock cylinder i dont think good things would happen !!!

 

[codykeon18]

I have a top end knock also never figured out what it was but my quad is still running stron and it knocks pretty loud almost sounds like the piston is hittin the head but I had my moto apart and the head dont have a single mark in it. So not sure what it is. I run 93 pump gas premixed 32:1 with amsoil.

 

[Unstock240]

My uncles cr250 sounds worse than mine, and said it has ran about 7 years on the same top end. Since all is good I will just run it with 93 and have to deal with it until I eventually get a BB and stroker.