Can primary vent be plugged off ?

Bottom End (crankcases and crankshaft)
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oldbob
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Can primary vent be plugged off ?

#1

Post by oldbob »

I am doing a rebuild on my 48 UL and am wondering if the primary chain oil vent can be plugged off with a threaded plug in one of the case passages. I run a belt drive and it is still getting oil with the oiler shut down all the way. Is the vent necessary to vent the cam chest ? The cam cover has a vent . Would plugging it of make for more friction and heat ? Would it effect the oiling of the engine in any way ? Would it add to much back pressure to the pistons down stroke ? I have read of the vent being run to the out side of the primary but why vent it at all if oil loss is the only result .

Robert
crasha51pan
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#2

Post by crasha51pan »

I believe the crank case needs that "breather tube " open. What I did (because I ran a primary belt drive) was to run a piece of tubing off of the breather tube and drilled a hole in my inner primary and routed the tubing thru it and under the bike. The amount of oil getting by the chain oiler, once it was shut off was not that much. It worked for me....
oldbob
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#3

Post by oldbob »

Thank's for the reply Crash

I think panheads have the primary chain oiler vent as it's one and only vent . Flathead UL's and 45's have a good size vent on the under side of the cam cover. I would not consider closing off the vent on a pan but on a flathead with two vents I wonder if the primary vent might be more for oiling the chain than venting.

Robert
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