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genuine yz250 base gasket problems

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hi guys

recently switched back to yamaha with my yz250.

i fitted a new piston and top end gaskets about 6hours ago and every part i used was genuine yamaha. the last time i rode the bike it was losing coolant and wasnt running too good. checked the rads and the hoses and it was all fine, took the head off to see if it was the orings, they looked fine but i fitted new ones anyway. built the bike back up, started it, and could straight away see coolant pouring out from the basegasket right under the exhaust.

stripped the bike back down, took the base gasket off and the gasket seems to have dissintegrated. built her back up with a new gasket and shes fine.

so basically just wondering if anyone has had this kind of problem with a genuine gasket before where it seems to have disintegrated? ive used an after market gasket now and it seems to be a lot better quality than the genuine one.

cheers

ben #12

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I wonder if your lower cylinder surface, or case surface, is warped. In ordinary circumstances, that gasket does not do much. It would never be strong enough to seal a warped surface..think 99 Dodge Neon here....

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Check if your new gasket leaks on the right side (pipe side). I've had this problem on my 06, and I know of some other guys who had it on their 05s.

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At first glance I was going to say only use oem gaskets after disecting how various ebay generics worked for us in the real world.

But that does not apply to you. I had the same problem on our 89 yz250. Can't say the performance was any different but you could see liquid puddle up on the right side and blow the gasket. One time this happened in winter and I thought it was the environment. But the last time it did it in hotter weather 2 rides in a row.

I used gasket remover stuff and made sure that I got all surfaces clean, sometimes there is a little bit of buildup of old material.

Anyways last time I used an oem gasket and tried something I read elsewhere, permatex copper gasket spray. I got a can at kragens for less than $10

I used it, followed the directions and gave the gasket a couple coats and installed it and the bike has been on that topend through half a year of some good riding :)

I am not techie though and do not know if this stuff changes engine characteristics or not? We are just average joe trailer riders and would probably not notice the difference.

I am going to be doing the top end on my cr250 this week and I am NOT going to use the stuff, only because there is no hint of a problem.

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That spray is good for any gasket. It stops it from sticking when you remove it. Scraping time is cut down to nothing.

I love it.

Plus, you can spray your hand gold and look like the tin man on Wizzard of OZ.

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