Replacing Pushrod Tube Seals on Fiona's BMW Engine

April 18, 2020 through April 22

Another isolation period task begun.  The replacement of the leaking pushrod tube seals on Fiona, my '99 Ural Patrol with the '84 R80 RT Engine.  They'd been leaking pretty badly for a while now so it was time.

I used as my guide, the excellent video and tutorial put out by Brook R., Airhead Guru and fellow member of the Colorado Airheads Club:

Top End Disassembly - R100 RS

Note: it would take me about six hours to do the disassembly and five and and a half to do the assembly.  Going very slowly and consulting the tutorials at each step.

First, had to separate the sidecar from the tug so I had access room to the right jug, aka Head/Cylinder.  This proved not too problematical but it did require assistance from my son Patrick in holding things up while jack stands were positioned!

I slavishly followed the posting containing the tutorial created by Brook so I won't replicate his fine photos showing the process.  I'll just add pics that were specific to Fiona's engine:

 The right and left rocker assemblies and pushrods, labeled as to

origin/placement and which end of the rods was TOP or out to

ensure they go back same place, same way.

 A peek at the left side's connecting rod, 

supported by zip ties so it doesn't fall and

hit the side of the engine case's opening.

 Left Head ready to be removed

 The heavily carbonized piston face of

the left cylinder

 Separating the head from the cylinder

 Another view of the heavy carbon buildup on the left piston's face

 Yep, that's oil seeping past the piston.

Oil ring was examined and found to be same in terms of gap

as the oil ring on the right piston so unsure of where the oil

is coming from.

Left side taken apart and ready for cleaning.

Then it was time to repeat all above steps for the right side jug/top end:

 The right side's head's valve area, not as

badly carbonized as the left side and no oil seepage

 Right side piston face, not as badly carbonized as the 

left piston but still pretty bad I thought.

Cleaning up the engine case once the jugs were off took a bit of time as well as cleaning all the removed components.

I used Simple Green at first, per Brook's recommendation and even after two nights of soaking and several scrubbings with steel brush and other implements, there was still carbon on the pistons and left side head:

 Top piston is right side, bottom piston left side

 left head

right head

So on Day Three of cleanup, Apr 21, I got some Berryman Chem-Dip Parts Cleaner from the Auto Parts store and after an overnight soak and much more scrubbing and scrapping, finally got all the items cleaned up for installation!  So much work, the cleanup!

Today, Apr 22, 2020

Started the re-installation of the top ends on Fiona.  Did spend some time trying to ensure that the oil rings were remounted with the correct side facing up.  These were the old type apparently and not labeled with TOP to ensure no mixups as per the tutorial.  Instead, Brook pointed me to a spot on Snowbum's website on how to determine the top side.  I think I got it right, we'll see.  If not, I see new rings in my future.  

Why  just the oil rings?  Because unlike the top and middle rings, I'd removed the oil rings to insert them into their respective cylinders to measure the gap when compressed to see if the left side ring's gap was bigger....they both were the same.  So, the theory was, no new rings required.  Most likely its seeping past the left side head's valve guides but I elected to not replace them this time, both because of lacking the special tool to compress the springs and just trying to stick to main task.

Following the installation tutorial:  Top End Install - R100 RS

I started again with the left side:

 Photo verification that I put the head gasket on correctly

as you can put it on backwards and slightly askew.

Unfortunately, I failed to check the orientation of the pushrod tube seals and after I'd progressed to the point of mounting the rocker assemblies, I thought to check and found them backwards!  Dammit.  So off came the head, pulled back the cylinder, removed and re-installed the seals correctly and pushed the cylinder back on:

No matter how much I wiggled and pushed on the cylinder I couldn't get it to mate closer than below pic:

So I went ahead and installed the left head:

Once I mounted the rocker assemblies, I was able to use them to mate the cylinder base to the engine case, using slow and methodical tightening of the nuts holding the rocker assemblies to slowly and evenly mate the cylinder to the engine case.   Note: I used criss-cross pattern to ensure even contact.

I completed the assembly of the left side top end without further issues except for tightening the rocker assemblies without ensuring the push rod ends were clear of the tappet's cup.  So they ended being pressed a bit but was able to free them up by loosening the adjuster nut.  I wouldn't make this mistake for the right side jug!

Right side:

 Photo evidence re head gasket placement and condition/orientation

of the right piston before installing the right side head.

No big issues with the right side head, did have some trouble getting the wrist pin in to secure the piston to the connecting rod but finally got it in without resorting to wild hammering.  Patience is something I continue to learn apparently.

Got the right side top end installed by 2PM, started around 8:30 I think.  

Here's photos verifying placement of the pushrod tube seals, both left and right side.

 Assembled right side top end

Assembled left side top end

That's it for today, tired and back is hurting in spite of the elevated position of the motorcycle and use of a stool.  I'll put Fiona back together tomorrow after the final torque check of the rocker assembly nuts; you're supposed to let them sit overnight and check again for the final torque setting of 25 ft/lbs.

My thanks to Brook Reams, airhead guru mechanic par excellance!

Update, April 23: got Fiona assembled up and mated to the sidecar after a brief running of the engine to ensure no bad sounds or explosions.  Took her for a short test ride, only about 14 km but she did well, still no explosions and no obvious leaks yet.  I'll check her later for seepage.

Update, April 24: no seepage but found the left intake tappet way loose, the top end of the push rod was barely in the cup!  I must have not tightened the nut securely enough before yesterday's test drive.  I set the valve clearances to spec this morning, did a test ride around Noon, all seems well except for some minor oil leaking out of the left valve cover.  Applied some Yamabond sealant and we'll see.  Otherwise, all OK!