I completed work on the front of the engine when I replaced the timing chain, crankshaft timing gear, front main seal and crankshaft nose bearing. I also replaced the three seals in the timing chest cover. You can see how I did that work here:
So the next area of work is the rear of the engine. I removed the clutch and had it refurbished by Southland Clutch. I removed the flywheel, replaced the rear crankshaft main seal and the oil pump cover o-ring. While I had the pump cover off, I measured the clearances of the oil pump gears and found them all good and toward the low end of the allowable wear limit. Here is how I did this work:
- 21 BMW 1977 R100RS Remove, Refurbish, Install Clutch
- 11 BMW 1977 R100RS Replace Rear Main Seal & Oil Pump Cover O-Ring
I added a new full advance timing mark to the flywheel at 25° BTDC. I have dual plug heads and the advice from Tom Cutter at Rubber Chicken Racing Garage is to retard the full advance by 6° by retarding the “S” timing by 3° and limiting the full advance by another 3°. Before doing this, I did some digging to learn more about the flywheel in this bike and the automatic timing unit (ATU) and documented BMW flywheel changes in the /5, /6 and /7-R100 series of motors and the ATU’s. You can find that information here:
- 12 BMW 1977 R100RS Changes To Ignition For Dual Plug Heads
- 12 BMW 1977 R100RS Install Dyna III Electronic Ignition-Refurbish Automatic Timing Unit (ATU)
Next up is to remove the pistons, rings and connecting rods, see how the rod big end bearings look, remove the rings, clean the pistons and inspect them and then make decisions about what needs to be done.
Here are a couple pictured from the write-up.