Thursday, August 3, 2017

Sunbeam S7 Deluxe - Crankcase Breather

I recently met up with a nearby Sunbeam owner from Lancaster County (across the river).  We compared our machines and discussed improvements and modifications.

One thing that my friend noticed was the crankcase breather on my Deluxe.  I wanted to avoid fouling plugs, and a disturbed mixture, so instead of routing the breather back into the air cleaner, I used a road tube.  Since there isn't much opportunity for a "draft tube" like on a car, another method was in order.  The standard breather "check" valves stopped working of course.

I obtained a brake booster check valve from Dorman products and mounted it alongside the frame rail, just above the side engine damper.  Since the valve's inlet port diameter was quite large, it needed to be reduced.  So I put another hose inside that one.  The outlet tube then goes along the frame rail behind the silencer.

The larger port is the inlet, the smaller one on the side is the outlet.
Part #: 80189

The brake booster check valve insures that crankcase is well vented.  The front of the engine stays clean, and the vapors are deposited well behind the rear wheel.

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