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athena bb problem

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just bought a 2005 yz125 with a athena big bore kit about 2 weeks ago and have went through 3 sets of cylinder head o-rings. there has to be something wrong it runs fine until it spits all the water out into the cylinder and dies. I think it has too much compression or something. the o-rings last about 5 hours and are done. could it be the base gasket is wrong or too thin??? any ideas?

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Sounds like the head is not flat or possibly the cylinder. Try some ultra fine sandpaper on a piece of glass. Move the head in a figure 8 patern to repair. Check after one pass to see the high and/or low spots. If its okay it could be the cylinder surface, but due to its mass, its more likely the head.

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i am not 100% but I think i heard something about there being a bad batch of O-rings sent out for the athena kits.

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I swear there was a thread about this very thing a while back. I will try a search, but I dotn believe this si the first time we have seen people with this problem.

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I have an Athena kit on my 06 YZ125, and knock on wood I have not had any problems with it. I have 10 hours of running time on the kit.

When you replace the o-ring did it fit or did you have to strech it to make it fit? If you had to strech it then it was not the right one it should just lay right in place.

Also your squish clearance could be to small. It should be set at 1.1MM for the 144 kit.

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thanks for the help and links. the head was warped so we sanded it down carefully and will see if it works. the bolts are all tightened to specs and o-rings fit nicely. hopefully this will fix it. thanks again.

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