T140 engine and frame breathing

Chaps,

The stock oil tank / frame breather on the T140 E simply connects the frame, from underneath the top spine just behind the steering head, to the top of the exhaust rocker box.

I’m thinking of using that rocker box breather as an engine breather, which would necessitate doing something else with the frame breather (I’ll be using a reed valve breather so need to isolate this from the frame breathing, so teeing them together isn’t an option).

My question is, how likely is it for oil to come out of that frame breather, ie under heavy braking etc, anyone know?

Bet nobody knows, but even if the oil level sometimes sloshed up near it, there isn’t much pressure to drive oil out.

As a side note Nigel I used to run my t140 e with an open primary
I blocked the 3 oil leveling holes but never fitted a crank oil seal it didn't need one, oil never came out
None that I noticed anyway
All I had was the centre web from a scrap chain case to support the gear cross over shaft

My approach was to mount the reed breather upfront under the tank, just above the exhaust rocker box, run a length of hose from the breather down under the tank to a brass fitting tapped just above the oil filler cap. Stock tank breather gets no oil that I can discern, I have it running to a catch bottle under the seat. Some stainless mesh wedged into the outlet hose from the rocker box prevents excessive oil from making its way through the breather

Let me just check I’m following your plumbing correctly...

You‘re breathing the engine into the reed valve, then from reed valve into the frame, then allowing the frame to be vented to atmosphere via the normal vent under the spine behind the headstock, is that right?

And you get no oil out of the frame vent?

Can you tell me where you get that reed valve breather from with the inlet and outlet facing the same way?

One more question, where do you take the engine breather from?

Can you tell me where you get that reed valve breather from with the inlet and outlet facing the same way?

Click to expand...

Searching EBay for “egr valve Yamaha” or variations thereof can bring them up.

Fast Eddie said:

Let me just check I’m following your plumbing correctly...

You‘re breathing the engine into the reed valve, then from reed valve into the frame, then allowing the frame to be vented to atmosphere via the normal vent under the spine behind the headstock, is that right?

And you get no oil out of the frame vent?

Can you tell me where you get that reed valve breather from with the inlet and outlet facing the same way?

One more question, where do you take the engine breather from?

Click to expand...

That's correct, pretty much the same arrangement as in the norton (engine breathes to oil tank etc.). The exhaust rocker box is the later version with the vent pipe. No oil from the oil tank breather, stock outlet hose, just run to a catch bottle. I actually have a 2nd reed breather off the rear primary vent that runs into the same catch bottle

The reed valve is the current iteration of the yamaha XS breather, I think I snagged it from Mike's XS