Author Topic: Catch can / Oil separator  (Read 2016 times)

Offline spottycat

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Catch can / Oil separator
« on: 20.05. 2025 09:26 »
Hi,

I was just wondering if anyone had experimented with a catch can/oil separator from the breather. I guess that over time even a well running machine will have some oil mist exiting from the breather which, given it is just a hole in the crankcase, will spray onto the chaincase and be messy and ultimately drip. My concerns about making a catch can would be increased back pressure, potentially making the problem even worse. Failing a catch can, I thought that maybe just a short length of tube would prevent any oil spraying onto the engine and chaincase and making a mess, even if ultimately there was a some oil dripping from the tube.

Would be interested to know if anyone has tried anything.

Cheers, Chris
61 A10

Offline Worty

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Re: Catch can / Oil separator
« Reply #1 on: 20.05. 2025 11:31 »
I haven't, but I think someone on the Forum tapped the hole and put a pipe on it to divert it somewhere??
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Offline chaterlea25

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Re: Catch can / Oil separator
« Reply #2 on: 20.05. 2025 12:23 »
Hi All
Any tube that is fitted into the breather hole will reduce its size ( unless case is modified)
which is a bad idea *ex*
If the engine is in good mechanical condition and the cork washer on the breather "tight enough" there should be minimal oil coming out the breather.
If the bike doesn't have an enclosed chaincase the vapours help lube the rear chain ;)

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Worty

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Re: Catch can / Oil separator
« Reply #3 on: 20.05. 2025 12:46 »
Quote
If the bike doesn't have an enclosed chaincase the vapours help lube the rear chain ;)

If not the rear tyre *pull hair out*
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Offline Swarfcut

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Re: Catch can / Oil separator
« Reply #4 on: 20.05. 2025 13:41 »
 Early bikes, Rigid and Plunger models, had a small bore copper tube leading down past the sump plate, with a P clip on one of the crankcase through studs, adjacent to the sump plate. Later on this was shortened to lie under the chain guard mount at the back of the primary chaincase, exiting oil vapour onto the top run of the chain.

 Swinging arm models have just a hole. A counterbore for a spigot (some folks use a roll pin) and flexy pipe down to the lower chain run will give a homespun chain oiler and a little less mess behind the chaincase. As mentioned whatever is done should not obstruct the hole.

 How it works is still a mixture of alchemy and faith, and yes on a good motor there will not be much coming out.

 Swarfy.

Online berger

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Re: Catch can / Oil separator
« Reply #5 on: 20.05. 2025 15:16 »
i threaded my hole  *eek* and put a brass tube in and then put a piece of stiff reinforced plastic tube on that with an elbow in the end that sits 1/2 an inch from the bottom chain run on the gearbox sprocket

Offline Adler

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Re: Catch can / Oil separator
« Reply #6 on: 20.05. 2025 17:34 »
Hello, on my plunger GF there ist just a small plastic pipe from the hole at the rear of the crankcase as described before and shown in the Screenshot below.
Best regards. Manfred
Germany SE (Bavaria)
1950 A10 GF Plunger (and some German motorbikes from '33 to '54)

Online berger

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Re: Catch can / Oil separator
« Reply #7 on: 20.05. 2025 18:11 »
in the pic you can see a clip on the pipe at the brass tube end and the elbow fitted to the tube and any mist gets blown onto the chain