Vintage BMW Motorcycle Owners

We are looking at installing a new (cast in pins) breather plate onto a 20 degree cam gear.

When the single pin breather plate is used there is a thin flat steel plate that blocks off all the holes in the cam gear.
Does anyone know what the function of this plate?

We are thinking of removing the plate but don't know what the consequences might be.
Any thoughts would be most appreciated.

We are also looking at scrapping the spring system and replacing with the wave washer system.
Any thoughts on that as well.

Mal and Doug

This parts book is relatively clear on what you need: https://www.bmw-einzylinder.de/Start/ti ... X_1966.pdf

You need the new breatherplate with the pins as part of the casting. You also need the wave washer. And you need a 1mm thick shim.

The old springs doesn't work. It will be fully compressed.

Mal,

In my opinion, as long as you have the correct spring pressure to push the breather plate against the front cover and seal it you are fine. The older 1 pin breather had a coil spring that pressed against it as well which makes me feel there is more spacing between where the spring sits on the cam gear and the breather plate, but I have no measurements to back this up.

I would check this and if needed, put a spacer behind the new spring to get the right pressure on the breather plate. Even if the parts book specifies a list of parts, I would still double check it!

jwonder wrote: ↑

Mon Nov 14, 2022 11:55 am

Mal,

In my opinion, as long as you have the correct spring pressure to push the breather plate against the front cover and seal it you are fine. The older 1 pin breather had a coil spring that pressed against it as well which makes me feel there is more spacing between where the spring sits on the cam gear and the breather plate, but I have no measurements to back this up.

I would check this and if needed, put a spacer behind the new spring to get the right pressure on the breather plate. Even if the parts book specifies a list of parts, I would still double check it!

Thank You James.

I will report back on how we get along.

Mal

Seek wrote: ↑

Mon Nov 14, 2022 10:52 am

This parts book is relatively clear on what you need: https://www.bmw-einzylinder.de/Start/ti ... X_1966.pdf

You need the new breatherplate with the pins as part of the casting. You also need the wave washer. And you need a 1mm thick shim.

The old springs doesn't work. It will be fully compressed.

What a beautiful and clean publication.

Thank you very much.

Mal

Hello all

I believe Jwonder mentions a point of interest, I just having some problems with my last rebuild, so any inputs will be a good help,

Here the facts:

Few months ago I complete a full rebuild of the bike (R60/2 1969) after a major failure caused by previous owner, who changes rear oil seal, and while putting flywheel again, drops the keyway out of crank end, causing it crash on bearing cage when it blocks it movement, this causes a ton of metal debris inside the engine that damages oil pump, crankshaft, pistons and other internals.

I make my self a full rebuild, including a used crankshaft (which I rebuild in my home workshop). Re sleeved cylinders, new pistons and of course a new set of timing gears.

After start up I notice that have too much internal pressure, and after a few milles have some oil leak on pan, since I had a cork gasket I guess it was caused by poor fitting, so changed to a paper unit, but after a few small trips, a new leak on pan again.

Since I have at least 10 years without driving this bike, I forgot how much pressure does it has when you put out the dipstick.

Today I disassembly engine, didn't find any wrong on breather disc timing, as mentioned by MAlmac, just its circlip loose at the point that didn't hold breather, but since it seat against cover, didn't believe it was the main fail cause.

Tomorrow I will check pan for a perfect flatness, but will appreciate any input.

Kind regards

Rodolfo Castillo
Guatemala

Rodolfo, do you have oil on the tray in the rear of the engine?

No i didn't find any oil.

Looking at Malmac Post, found that need to perform a Pressure leak test, maybe my piston rings didn't seat .

just check oil pan and isn't really flat, but not enough for the amount of oil leaks.

Vech´s post says something about combining breather with timing gears (which I have done on this bike), looking at mine, from timing mark in CW hole starts near 3rd tooth of timing gear, I have at least 4 more timing gears with breather discs, so will make a good check.

I feel that I have too much internal pressure inside engine, maybe caused by piston rings leak. Oil (new with less than 5 milles) seems to have carbon buildup, caused by burned oil.

Re sleeved Cylinders have 72,00mm bore, and pistons are 71,92 mm. STD Pistons from Uli´s, Piston Rings KS.

thanks for your help

Regards

Rodolfo

"No i didn't find any oil.

Looking at Malmac Post, found that need to perform a Pressure leak test, maybe my piston rings didn't seat ."

I have a rebore and new pistons and the leakdown test showed quite a bit of gas leak past the rings - hopefully will get better once engine is run in.

"just check oil pan and isn't really flat, but not enough for the amount of oil leaks.'

Often the oil leaks down the threads that secure the oil pan - even if pan is flat and gasket intact.

" Vech´s post says something about combining breather with timing gears (which I have done on this bike), looking at mine, from timing mark in CW hole starts near 3rd tooth of timing gear, I have at least 4 more timing gears with breather discs, so will make a good check."

If your cam gear has only two holes, not really possible to put breather in out of time, without leaving out woodruff key on camshaft or having the wrong valve timing.

"I feel that I have too much internal pressure inside engine, maybe caused by piston rings leak. Oil (new with less than 5 milles) seems to have carbon buildup, caused by burned oil."

What about wear in your valve guides?

This is also interesting, a breather with enlarged holes to reduce crankcase pressure even further:

https://bmwclassicmotorcycles.com/index ... ation.html