compression issues

[xjma]

why holy crap?? Was it running lean and scored the cylinder bore real bad?? If there is evidence of blowby on the headgasket, I would say that could be why you were only at 30 psi. You did kick it over multiple times to get a consistent reading, right? No, the reeds won't matter in a compression test, but I'd check them during a rebuild.

Does the bottom end need help too?? Remember, you should have a machine shop do the work BEFORE you order your new piston!! Tell them to call you ASAP once they know how much they are boring it to. They really can't tell until they start boring it though.

I recommend doing the rings at least once a year...more often if you ride it hard a lot. Getting a look at the piston and cylinder is even better than a plug check in terms of figuring out if you're rich/lean.

Oh yeah, and you should be cleaning the air filter every ride or so when it's dusty!! It is kinda a PITA, but it's cheaper than having to bore the clyinder out every year!! And a clean air filter means more power!!

 

[98blaster+4]

basically from what i can tell the previous owner relied on the oiling sytem,which is junk,and never mixed the gas hence making it cook the piss outta everything now im just waiting to get paid to have it bored up .
i was thinking of goin with a .030 overbore this time and when it needs it again going with the vitos240

 

[xjma]

basically from what i can tell the previous owner relied on the oiling sytem,which is junk,and never mixed the gas hence making it cook the piss outta everything now im just waiting to get paid to have it bored up .
i was thinking of goin with a .030 overbore this time and when it needs it again going with the vitos240

Just give the cylinder to a machine shop and they will tell you how much they're going to bore it. Why bore it out more than you have to??

 

[98blaster+4]

well the way i fugre it it'll prolly snow here before i can get it done ,that way i will start making better money and get some go fast goodies
and besides like they say GO BIG OR GO HOME!!!!
and i got no ride home

 

[Superjet11]

Remember, you should have a machine shop do the work BEFORE you order your new piston!! Tell them to call you ASAP once they know how much they are boring it to. They really can't tell until they start boring it though.

That is wrong. The bore is fit to the piston. How can you expect the machine shop to set up your jug with .005 clearance if they do not have the piston in their hand? I agree that you man need to take it to them to evaluate the scoring, and tell you how big you need to go, but having them bore it without the piston is a very shady way of doing it.

 

[98blaster+4]

well the piston is all shaved off lookin but the cylinder itself doesnt look bad at all but im not gonna cheap out on it because im abusive and i dont feel like replacing the whole bottom end tooanyways thanks for all the input ,hopefully this helped out somebody besides me
peace

 

[cirame1]

its probably junk but i bet u didnt do the test right. theres a bunch of factors in a cr test i have never done one for a 4 wheeler but with cars we do at least 6 clicks and at wot. i dont know how u did it but 30 seems very extreme.

 

[98blaster+4]

well the piston is out of round, it has scrape marks on the two sides of it where the wrist pin goes through
the rings are melted directly to it in some spots and otheres it is broken
and on spot the metal is ground off through the ring so that you can tell there was a ring even there
and the top of it looks perfectly normal