Loss of compression

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Loss of compression

Postby 357ross » Wed Mar 31, 2010 2:51 pm

Hello all, I recently bought a used K&B 61 engine. When I first got it, the bearings felt super smooth, and the compression felt excellent. This engine has a ringed piston. I mounted it on a test stand and fired it up. The fuel I was using is 10% nitro, 16% oil. The engine seemed to run really strong. After about half a cup of fuel, it quit. Now it has very little compression, and even after putting after-run oil in it, the bearings feel a little gritty. My question is have I ruined my engine, or is this a part of the break-in process? Thank you for your help.
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Postby MECOA » Fri Apr 02, 2010 10:42 am

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Postby 357ross » Fri Apr 02, 2010 12:43 pm

Thank you for the info about the fuel. I took the engine apart, but I don't see any evident wear in the cylinder, or on the piston. Can I fix this with a new ring and bearings, or would I be time and money ahead to replace the cylinder liner, piston, and con rod? Thanks again.
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