Non Vented Final Drive on my ‘55 R50

[flyingtpot]

Recommended that you do it Mal. For you, it is a straightforward design item. The time to do the mod is definitely best when the housing is 'empty'.

I may have what flyingtpot is referring (or it's a custom job). I have a 1956 R69 where the final drive has had a vent added by previous owner. Body of 'vent' is aluminum, and the vent hole is about 1/16" dia. I grabbed a piece of wire and stripped it back about 2.5" and fed it into the hole, and it appears to go all they way straight through.

The main drive casting looks like it had a flat (slight counterbore) machined into it for this to sit flat.

What an interesting post. The photos are good and the idea quite achievable.
You have me thinking, as I have a non vented final drive that is ready to be rebuilt with all new bearings and seal.

Thanks.


Mal

[flyingtpot]

The key is a small through hole and a 'reservoir' type design.

Having done both types (fill plug and top of housing) of these design mods, my preference is the top of the housing. The gear oil level is than the furthest distance from the vent hole.

It's a pretty straightforward job. I made a very small (about 1.5mm) hole from the inside of the plug through to the outside, then enlarged it only part of the way through from the outside. So any oil that comes through the 1.5mm hole will hopefully collect in the 'reservoir' inside the plug. Then I brazed in the vent plug.
Once I get the bike back up and running I'll follow up to let you know if it works. If not, I still have undrilled plugs

[CWRoady]

This one looks promising if my version isn't as successful as I anticipate it to be.

https://www.kartgeneration.it/gb/kart-s ... &results=1

[malmac]

Recommended that you do it Mal. For you, it is a straightforward design item. The time to do the mod is definitely best when the housing is 'empty'.

I may have what flyingtpot is referring (or it's a custom job). I have a 1956 R69 where the final drive has had a vent added by previous owner. Body of 'vent' is aluminum, and the vent hole is about 1/16" dia. I grabbed a piece of wire and stripped it back about 2.5" and fed it into the hole, and it appears to go all they way straight through.

The main drive casting looks like it had a flat (slight counterbore) machined into it for this to sit flat.

What an interesting post. The photos are good and the idea quite achievable.
You have me thinking, as I have a non vented final drive that is ready to be rebuilt with all new bearings and seal.

Thanks.


Mal

Yes I will give it some thought. It is just I have some other projects which have to come first. The next one is building the frame for my son's K1100 to mount his side car. He has a K100 with sidecar but the frame on the 1100 ends up being different so we need to make a whole different framework.

So the vented diff housing will have to wait in line.

Mal

[CWRoady]

So I am really starting to feel confident the vented plug will work. With no fill plug installed at all, and 150cc's of oil in the FD, I put a 22mm socket on my hand drill and ran the FD at full speed of the drill. Not one drop came up to the opening.

[schrader7032]

Quick, write BMW with the idea! I'm sure they thought of that and it was a much simpler design that altering the final drive housing. But then I'm sure they were concerned about the oil level being so near the plug and they didn't want a lawsuit on their hands.

[CWRoady]

Not there yet ... likely needs a larger reservoir. Just did a little test ride and the first couple of stop and checks had me smiling. One after a short little freeway jaunt had a dribble. Thinking of adding a couple of baffles and a taller stack. Not ready to give up on the vented fill plug yet

Edit to add that this looks like it may be the ultimate answer https://bmwclassicmotorcycles.com/index ... -dome.html

[flyingtpot]

Check out some of Lowell Neff's (Neff's Engineering) K-bike sidecar machines. They are well thought out and executed sidecar designs.

[/quote]

Yes I will give it some thought. It is just I have some other projects which have to come first. The next one is building the frame for my son's K1100 to mount his side car. He has a K100 with sidecar but the frame on the 1100 ends up being different so we need to make a whole different framework.

So the vented diff housing will have to wait in line.

Mal
[/quote]

[flyingtpot]

As a one-off idea, the vented filler plug is acceptable.

When these machines were designed, BMW would not allow a service item like a filler plug serve as the production FD vent design. For BMW, designing the FD with a housing having a top mounted vent was trivial on this series machine.

[CWRoady]

Flyingtpot, I don't know why I didn't follow up with you when you said you had tried the 9:00 and 12:00 locations and had a preference. I sent you a PM asking for the benefit of your experience and some advice.
Chris