.090 or .010 over jug on 85 250r? rebuild questions

[200x_Basket]

after dans sandbar ride my 250r quit on me. i changed the head gasket but it was still running bad. after running a compression test i cam up with 80psig. the curreng jug is at .080 over but it is ported. i also have a standard bor that i could have bored to .010 and i would be back on the trail. how far can i safely bore the 250r?
thanks
chris

[Mr. Richard]

i have heard that you can bore a 85-86 cylinder to .120 over i am at .o80 on one cylinder too , so i hope they can,,,,,,,

[dunerash]

I think your right KASEY, but heat becomes an issue when you start boring it that far:( 200x_basket: You need to bore it? cant get away with just hone huh.. did it blow a h/g? what was your compression at before? And what the heck is a Trinity head job?..:D

[200x_Basket]

i never lost any water so i dont think i blew a head gasket. i changed the head gasket anyway and it only had about 80 psig compression with the throttle wide open. i may gat away with a hone but i have not torn it down to see.

www.trinityracing.com

[dunerash]

Thats cool.. mines at .080 now and had it honed and new piston(wiseco pro-lite)/ rings done last winter, he said i still have a few more bores if needed:) Please dont get discouraged and jump ship on the 250cyl..You CAN get them to run with the big boys..and my opinion on going to a cr500 setup:thmbsdwn: besides being a ton of work.. your hacking up another perfectly good atc frame:confused:

[Rocketman]

Were you running the CR head gasket? Do you think that caused you problems?

[200x_Basket]

i was running a cr head gasket but this is just a junkyard motor. i have no idea how many hours are on the pison and rings. i am about to tear it apart to see if i can get away with a hone and a set of rings, but at 80psi i doubt it:(

[Fuzzy]

Try putting a little two cycle oil down the spark plug hole and doing another compression test. If the compression increases then it is your rings causing the problem. I wouldnt bore a cylinder unless it had a ridge that had to be removed. You would be surprised how much a hone job and a new set of rings and gaskets will do for a motor. And 80 psi isnt really that low. The 250r only runs about 8:0-1 compression. So with a ring job i think they push around 120 psi. But at least the oil test will help you to know if the problem is the rings. Or maybe cranks seals or something else in the motor.

[84200s/m]

fuzzzy
would that little trick of yours work on my bike also how much can a hone fix a have a scrach in my sleve

[markb]

don't sweat the overbores that thing can take them . i had my 87 jug out to .085 i think, i can't find the box now but i know it was a cr piston because the atc ones didn't go that big. they handle the 295 kits on the stock jug with o-ringing
84 200s/m remember when your "fixin" the scratch your increasing the piston to bore clearance which has it's own problems i guess it depends on your budget
200x basket don't listen to dune rash, get discouraged then sell me the motors
mark:thumbsup:

[Fuzzy]

It depends how deep the scratch is. And how wide the scratch is. The whole purpose of honing is to put some scrathes in the cylinder. So the oil has something to stick to. A small scatch wouldnt make any difference. I doudt you would even notice it as far as compression goes. The engine cant be completely air tight anyways. That why the rings have gaps to allow some air flow through it. So i dont think it would be any problem.