P11 oil tank to engine ID pipe diameter

Old English Sleep Dog · Jan 17, 2021

Bit of a newb question, what is the ID of the engine to oil tank pipes? I've measured the OD of mine and they're 20mm / 0.8in.

Having searched this forum and on line it's hard to find a definitive answer. My other bikes old and new are Italian, German and Japanese. Struggling to get my head around all the different thread and pipe sizes. Thought Italian bikes were extreme for using different sizes bolts on everything.

Thanks for any help.

EstuaryBoy · Jan 17, 2021

I seem to remember 3/8, hopefully others will confirm. Sure the original was quite thin walled too (neoprene?). Doubt that would still be available, though....

texasSlick · Jan 17, 2021

I think you need to be more specific. The number you cite is enormous for the various hoses or tubes between the engine and oil tank.

There is the oil junction block tubes, which is a dual rigid tube assembly that bolts up to the engine timing side case. It has tubes 3/16" ID and 5/16" OD.
Then there are the flexible hoses that lead from the oil junction block to the oil tank. These are 5/16" ID; the OD may vary from 0.5 to 0.56 inches.

Slick

Interbak · Jan 18, 2021

The oil pipes on P11s are actually 1/2 ID. I ordered some 1/2” oil line from Amazon, probably larger OD than originals. I have 1/2 herringbone on my P11A, pretty much impossible to find that stuff now. Commandos use the smaller hoses and fittings, 5/16 or 3/8.

Old English Sleep Dog · Jan 19, 2021

Thanks all for being super helpful.

@texasSlick I'm referring to the main oil pipes running from the dual crank feeds to the oil tank (pic below).

@Interbak not sure the ID is 1/2 on mine, the hose wall thickness looks almost the same thickness of the supply piping.

Interbak · Jan 19, 2021

The engine oil fittings are larger at the ends, 1/2”, so are the oil pipes on the tank. Both my P11A and Ranger are the same.

Old English Sleep Dog · Jan 19, 2021

@Interbak thanks for posting pics, 1/2 makes total sense now. I'll check mine at the weekend and reply.

mdt-son · Jan 21, 2021

See #24 here:

Difference between 3 start and 6 start oil pump?

Hey, Every time I put on six start in replace of 3 start I moved overhead rocker feed to bottom of the timing chest ala commando style, scrolled or not, I have ruined more cams by lack oil flow from head then any soft cam problems ever encountered. Never ran down Atlas cam tho! One trick was...

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