Single breather?

[SEDoan]

Why didn't Ariel route a crankcase breather into the primary chaincase? It would blow through the drive side main bearings so oil vapor would condense in the primary. I need to add a breather to my single (it has only 1 breather in the timing case) and thinking this might be a good solution. But it might be a terrible idea. What do you think?
Thank you!

[nevhunter]

It puts condensate and other crap with it. Better to use ONLY chainlube and oil bath. The Cam faced engine shock absorber needs good Lube to save it and the splines. Nev

[paul.jameson]

I have been running my 1937 RH500 (with later cylinder head) for many years now with just the timing case breather. Why do you need to add a breather?

[Roger Gwynn]

The factory added a 2nd breather on the drive side crankcase around the 2 o'clock position in 1954. More breathing was required when higher compressions and speeds arrived due to improved fuel and roads in the 1950's

[david.anderson]

While Ariel added an extra breather it was ineffective. It was added at a time when it was common practice to add extra breathers everywhere and many owners added those extra breathers in various locations, most commonly the rocker boxes and crankcase.
A 2 way breather sucks in as much or more than it breathes out. Any 2 way breather increases crankcase compression with the result that every gasket joint weeps oil mist. An engine breather should only breathe out.
I have always found that with a high compression engine (I run up to 10.5 to 1) there will always be a lot of oil pumped out the standard crankcase breather. In the rare instance that I use the crankcase breather I run the breather horizontal through a reed valve to the rear chain where it becomes the chain oiler, but often it over oils with high compression.
The Ariel can be improved by fitting a reed valve to the timing case breather and dispense with the ball in the elbow.. Then fit the HS crankcase oil seal to prevent air being sucked in through the mains into the engine as the piston rises, and do a good silicone job to the magneto oil seal. A reed valve is the only valve that will operate fast enough to exclude air being sucked back into the engine.
The VHA engine in the photo has the timing case breather elbow fitted upside down and the ball is removed. It breathes up through the reed valve and exits down through a breather hose. That engine is running 9 to 1 and does not weep oil at high speed.
My track built short stroke VH which spins up to 8000rpm has only the timing case breather through a reed valve.
Consider some of the vertical twins which pump a lot more air 650, 750cc of air to the VH 500ccs. Often they use a timed breather through a tiny hole.
David
(if anyone has a VHA timing cover that they are prepared to part with please let me know)

[Roger Gwynn]

I also use those Yamaha type reed valves feeding the rear chain. I tried the Enfield duck's bill and others but they are not as good.

[SEDoan]

Thanks guys. The reason I ask is that my '46 with a single ball bearing breather seems to pressurize at high rpm or wide throttle. I was wondering if a 2-way opening into the primary chaincase would allow the engine to vent pressure while drawing air from the relatively protected primary. It sounds like it needs the reed valve. Thanks for the picture!
I'm surprised that a 1/4" hole in the timing case is sufficient to vent the pressure of the engine at 6000rpm even with a reed valve so was considering adding a second reed valve at 2 o'clock in the drive-side crankcase. Is the 2 o'clock position the best?
Thanks,
Shawn

[Roger Gwynn]

It should be high up but anywhere will do, no doubt Ariel put it there as it was convenient for the pipe to run straight down, mine rises all the way to the rear of the bike and lubes the chain via the aforementioned Yamaha reed valve.