R80/7 Replace Pushrod Tubes

[jackonz]

So the bike came to me leaking oil badly, sump gasket was replaced and now its time for the pushrod tube seals, then dicovered that the rings on the tubes on this model can move on the tube resulting in leaks, so I purchased a set of tubes in S/S as well as all the gaskets from BMW Motorworks.
The story now is what setting from the barrel sealing face do you set these tubes for the ring to be in the correct place, I have both the Clymer and genuine BMW service manual for the bike and ther is no mention of the correct setting at all, all they talk about is pushing the ring on the tube closer to the crancase with a tool you can purchase or make, trouble is on these S/S tubes I am sure they are fixed in place on the tube.
Searching the net has confused me further as some say put a flat edge on the barrel sealing face and the ring area closest to the barrel should just touch, others say the same but 1.5 to 2mm lower.

For refrence the bike is a 1978 model and has no gasket or o ring onr barrel to crancase seal face.

I just want to do it once and get it right.

[Kurt in S.A.]

Searching the net has confused me further as some say put a flat edge on the barrel sealing face and the ring area closest to the barrel should just touch,

Do that. It's what Oak recommended.

Kurt in S.A.

[jackonz]

Yeah that looks to be the only setting I can find, now I have found that the S/S tubes I purchased from BMW Motorworks in the UK the rings on the tubes can move, am in two trains of thoughts here first is to spot TIG weld the rings in the correct place on the tubes, second is to Locktite them in place.
Had I purchased tubes from I think its Wonderlich they have a step in the tube to stop them moving back from the crancase.

[RPGR90s]

Loctite works very well for this application. No problems in twenty years.

[enigmaT120]

Mine do that too but the leaks aren't bad enough to worry about it and like you, I didn't know the correct distance.

I still don't know the correct distance but in a recent Airmail they printed an old article of Oaks in which he described a machinist's flairing type tool, a long skinny cone I guess. You use that to flare the ends of the tubes in the barrels. I've never seen it done but it sounded cool. I forget what he called the tool.

Can anybody clarify this line:

Searching the net has confused me further as some say put a flat edge on the barrel sealing face and the ring area closest to the barrel should just touch

Here's where a youtube video would be awesome.

[jackonz]

Well last night I did a trial fit of one pot with the new seals and had the collars set level with the gasket face, way too mch to compress without some distortion of the rubber seal, I asked a supplier of BMW parts in Australia and he said they should be level?
Brooks says they should be about 1.8 to 1.9 mm below so I have re set them as a trial last night to 1.85mm below the gasket face on the pot, I tried a fit and it looks much better with some compression to be made in the seal but not too much.

When I removed it all I tried putting a seal in place and then ran a stright edge on the crankcase face to see haow proud the seal sits above and as close as I could measuew its 5mm, so setting 5 below will in my view have no compression on the seal.

Unlike the tubes Brooks used the collars on the items I purchased can move in the tube itself but not as easliy as the stock tubes, so I have used Loctite 290 on the collars to secure them.
Iv'e had over 20 years experience in the engine reconditioning industry and know from expeiencew over tightening anything with a rubber seal is not a good thing at all, VW flat 4 engines have rubber seals on the pushrod tubes and have little or no compression as the tubes themselves have a deformable flexable spring type section this self adjusts to give the correct pressure.
I am surprised BMW have not given out a correct setting given that they themselves have changed the tubes some time in late 1980 to brazed collars, my factory workshop and Clymer manual have the tool listed to re set the collars, so in that regard the Clymer manual is out of date.

So tonight it's crunch time I am going to fit the l/h pot and see if I have to change it yet again.

[jackonz]

Well L/H pot is all back on and am very happy with the compression in the seals, I have now stripped off the R/H pot that had the worst leaks, what did I find well the tubes are lose in the barrel i could pull them out by hand no wonder it leaked so bad.

At least the new tubes are a very tight fit so should have no issues there, and no the bores in the barrel for the tubes were not damaged in any way.