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Title: Crankcase pressure relief valve
Post by: j hood on September 14, 2011, 09:23:15 PM

Hi..Has anyone got any details of the spring and valve plate that should go inside the relief valve. Mine started whistling and on inspection the spring and valve plate have disapeared. John

Title: Re: Crankcase pressure relief valve
Post by: phutton on November 05, 2011, 11:58:30 AM

Not sure which model you have, but mine (26 M5) just has the plate but no spring.

Paul

Title: Re: Crankcase pressure relief valve
Post by: j hood on November 07, 2011, 08:23:20 PM

1932 Model 9A Paul..John

Title: Re: Crankcase pressure relief valve
Post by: phutton on November 08, 2011, 02:57:47 PM

I don't know the answer, John, but I know a man who does! Ian Thompson commented:

The breather valve chamber contained a flat thin very light brass shim disc with a very light slightly conical spring above, which was opened by the pressure stroke air then closed for the rest of the cycle thus preventing air being drawn in on the vacuum. ie blow but no suck. These have all rotted away by now and engines seem to run ok without the internals. Manx Nortons ran open crankcase without problem and most Sunbeams post 1930.do as the rocker box has independent pressure feed.

I hope that helps.

Paul

Title: Re: Crankcase pressure relief valve
Post by: j hood on November 08, 2011, 07:07:31 PM

Thanks Paul. I had thought that to run it without internals should be ok..What confused me was where the Heck the internals disapeared to as they were there when I built the bike and i have only done about 70 miles on it..John

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General Category => Technical Discussion Forum => Topic started by: j hood on September 14, 2011, 09:23:15 PM