R80 Pushrod Tube Seals

The beemer has been typically reliable over the years - not least because I haven't used it much!  But that's one of the things I really like about it - you can leave it in the corner of the garage for a year, then dust it of and hit the starter button and it is ready for a trip around the country.  This time, though, I'm off to the South Island with some buddies so I want to address a few issues and give it a bit of a "birthday" before heading off.

This airhead has the usual leaks around the pushrod tube seals - just enough to coat the lower parts of the engine & frame and leave a few drips on the concrete.  Its an easy fix and a good opportunity to give it a good clean and check some of the internals.








You can see there is a good coating of oil on the underside.

Although not really necessary in order to change the seals, I split the heads & barrels, and removed them for a clean-up, decoke, valve lapping, etc.
















This picture shows a new seal (left) compared to the old one.  You can see that the sealing ribs are almost completely worn away.












Light honing marks still visible on the cylinder bores.  All good here.









I don't have photo's of the reassembly process, but I just lightly greased the oil seals before refitting the barrels and heads.   It all seemed to go into place easily, so I took the bike for a short ride, then put it back up on the table for re-torque, valve clearances, oil change, etc......







....... and found this.


All four of the new seals had split and ruptured during my 20 minute test ride.  Jeepers.

All four are completely munted - and I had to find out why pretty quick, coz off to Te Wai Pounamu next week!



A quick Google search revealed others who had struck this problem.  I had suspected poor fitting practise (by me) - and it turns out that nothing but engine oil should be used to lubricate the seals prior to fitting....

But that wasn't the problem at all.  Other people who had bought "pattern" seals from Motorworks in the UK had struck identical issues.  I bought these seals from Motorworks about five years ago (along with a bunch of other stuff) and got them sent over.

Its a subtle difference, but the "no-name" seal on the right is thicker at the base and the hole through it is at a slightly different angle (also no numbers & no logo).  This meant the seals would not seat properly in their tapered orifices, and the shoulder on the pushrod tube would eventually (quickly) rupture the seal.  Shame on you Motorworks!!!! I hope you aren't continuing to sell this crap.






I sourced some genuine BMW seals from Experience Motorcycles in Kingsland.  A whole $4 each!  Why didn't I just get them there in the first place?





This time around, I just removed the nuts from the long studs and took off the rockers.  The
barrel/head assembly can slide out far enough to clean up the mating surfaces and replace the pushrod tube seals.









NOTE:  loosen the nuts on the short head studs slightly and keep them in place - do not leave them torqued-up as you may warp the head.  ALSO: set the piston at TDC so the rings don't come out of the bore.