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Leaking front bearing

Old 03-20-2010, 01:24 PM
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Default Leaking front bearing

Bill, I read your post on front bearing leaking problems. I rebuilt my OS 120III pumper using new BOCA bearings and had you rebuild my regulator/carb and the engine has not run correctly sense. Yesterday I put it on the engine stand and fired it up. It does run but not correctly. The needle valve has almost no effect and it is only out 3/4 turn yet it is running very rich. I was able to get 9100 rpm and a low of 2100 with an APC 15X8 prop but it runs eractic. I discovered there was fuel flowing out the front bearing, not just the normal little drip. When I roll it over by hand it leaks a lot. I used an ear cleaning bulb and gave it a pressure test looking for any air leaks and the crank case pressure just blew out fuel and air from the front bearing. Could the BOCA bearing not fitting correctly or crank/case wear have any effect on the way this engine is running?? The pump is pumping and the regulator is regulating. If I put the engine inverted the fuel will keep flowing and flood the engine though. If it could be a bearing problem I will go into it again and replace them with stock OS bearings. Any help or advise at this point would be a big help. This one is making me crazy!!!
Old 03-22-2010, 09:09 AM
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Default RE: Leaking front bearing

The bearings don't "seal" the crankcase. Most of the seal is made by the close fit between the crankcase and the front bearing. The pumping pressure of the crankcase is used to force oil forward, through the bearings to lubricate the cam and rocker arm assemblies, and finally the front bearing. You should not get any oil flowing freely through the front bearing, however.

A severe leak through the front bearing should not compromise running, though, unless it's preventing the pressure pulses from operating the fuel pump.

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