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Compression difference


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Okay long story short, very little ride time on my combo. Started out with 180, 180 on gauge for compression i know its a little more because my tester is not as long as the plug. Anyways after a little bit off riding im at 180, 169. I spray some brake clean around my boss billet intake and it seems to be leaking on the right side a little (the 169 side). Bike would idle down really low when i sparyed it on that side.

 

Going to tear the top end apart and wondering if most reuse head gaskets(standard head, not cool head) and base gaskets? Also what should i expect, should i order some new rings this week just in case? I wanna reassemble and do a leak down test afterwards, i will also be doing a leakdown test as soon as i get the bitch out. Bike runs great and hard, just compression is scarin me a bit, i know they say 10 pecent, which would be around 18psi on this, but ive got so much money into this i dont want nothing to happin up at silver lake. ( oh and the right side which is the leaky side doesnt take well to slide height adjustment for idle, which is a another indication of a air leak).

 

 

Thanks

 

 

 

Cody

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well, i would expect to see a melted piston, not bad rings.......the leak probably happened after a few heat cycles, or from screw getting a little loose...........i had an airleak once where the boot clamps the carb, since the rubber was hard when i clamped it down, and it leaked after it got pretty hot. the carb was pretty glazed, too. i always hit them with sandpaper/emry/scotchbrite before i put them in now.

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Okay got a new piston and rings comein from FAST, hopefully everything will be cool when i tear her down!

 

 

 

Cody

 

 

 

Usually when the comp is that far apart after only a short amount of run time, there is a problem. Hopefully you find it.

 

 

B

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I was happy to see when you replied, any insight on what i may find?

 

 

Cody

 

 

I would expect to see that the rings are not floating free on the piston from localized heating from something. Keep in mind that new engines run hotter at the bore than worn engines. This causes ring heating and transfers to the piston. Al has a much lower melting point than steel so that will always show your heating problems. Double check jetting, carb balance, and timing. Shoot some pics if you like.

 

 

B

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I will for sure, im pretty sure its all from that air leak though. But we will find out, motor will be torn apart saturday and piston will be here on tuesday.

 

 

Cody

 

 

Be sure to inspect the bore carefully. Any Aluminum stuck to it will start this process over again. Good luck!

 

 

B

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