Pushrod Tube Specs?

[MikeL]

I just had a re-bore done on my '76 R75/6, and the shop apparently removed and re-installed my pushrod tubes- poorly. One tube is not inserted as deep into the cylinder as the other, and my stop rings have been moved up on one side.
Does anyone know proper measurements? End of tube to stop ring, stop ring to cylinder? Thanks

[Kurt in S.A.]

Based upon what I remember Oak Okleshen saying, the stop ring needs to be on the same plane as the base of the cylinder. But since the pushrod tube is angled, the stop ring will also be angled. If you were to extend the plane of the cylinder base, one edge of the stop ring should just barely touch this extended plane.

Kurt in S.A.

[MikeL]

Thanks Kurt, that makes sense, my "good" side stop rings seem to be just shy of the cylinder base. Any idea on how far the pushrod tube inserts into the cylinder head? I read flush on another thread, but I don't recall them ever being flush before, more like 1-2mm shy of flush. Thanks again.

[the quinner]

... and my stop rings have been moved up on one side.

You need new tubes...it sounds like they used the stop rings to remove or re-install the tubes. Once those rings are moved, they tend to just get loose and will move all around. Pushrod tubes should ONLY be removed and installed with the proper drift. If new tubes are being installed, the old ones can be removed (destroyed) with vice-grips. For installation, an old damper rod works perfectly as a drift (for the 1976 and later bikes)...I've also used an appropriate allen wrench socket. For removal with the intent of re-installation, on a properly made drift is appropriate. IIRC, Siebenrock sells the drifts for very reasonable money.

The tubes...when installed correctly...will be about 8mm below the head gasket surface (that's the 'biggest' dimension...the smaller dimension will be a mm or two).

To install: chill the tubes (and drift) in the freezer...heat the cylinder. One at a time, take a tube out of the freezer and immediately tap it to the proper depth. **it helps to remove/install one tube at a time...using the other tube as a quick alignment guide to start the installation**

[Garnet]

Hans @ Hucky's has the drifts as well. http://www.bmwhucky.com/010071.html