As I plan to replace the rear main seal, that is the rear oil seal on the crankshaft, inspect the oil pump and replace the oil pump cover O-ring, I need to remove the flywheel. On 1981 model year (the 1981 model year started in September 1980) and later models, the flywheel is also called the “Clutch Housing”, (part# 21 21 1 338 722).
I previously removed the airbox, transmission and the clutch so I can access the flywheel. You can see how I do that work here.
- 13 BMW 1983 R80ST Remove Air Box & Pulse Air System
- 23 BMW 1983 R80ST Remove Transmission
- 21 BMW 1983 R80ST Remove Clutch
The flywheel on the 1981 and later models (the 1981 model year started in September 1980) is different from the earlier models. It is lighter, for one thing and is mounted differently on the rear nose of the crankshaft. The procedure for removing the earlier flywheels (before September 1980) is different as shown in these documents.
The flywheel on the 1983 R80ST is the same as the one on the 1983 R100RS. I show how I removed the R100RS flywheel here. I’ll link to sections of this document as appropriate.
The tools I use are shown here.
They include a Cycle Works tool I got a couple years ago that I use to remove the guide ring on the rear nose of the crankshaft. Unfortunately this tool is no longer available from Cycle Works.
I put together a video summary of how I do this work on the 1983 R80ST.
VIDEO: 1983 BMW R80ST Remove Flywheel
Avoiding A Disaster
Before you remove a flywheel on any BMW airhead bike, you have to immobilize, or block, the crankshaft. This explains how I do that and also the reason it must be done to avoid severe damage to the crankshaft and engine block.
Set Engine To Top Dead Center (TDC)
The flywheel has the timing marks used to set the ignition timing. To ensure the flywheel goes back onto the crankshaft correctly, I rotate the engine so it is at TDC with the OT mark showing in the timing inspection hole in the engine block.
Remove Flywheel From Crankshaft
The overall procedure I use is the same as I show for the 1983 R100RS, but there are some differences in the technique I use, so I will show how I remove the 1983 R80ST flywheel in this section.
Add Index Mark To Flywheel
It is critical that when I install the flywheel, it goes back exactly as it was mounted when I remove it. The flywheel is secured to the rear nose of the crankshaft with five M11 bolts. I want to be certain that the holes in the flywheel match the same holes in the rear nose of the crankshaft when I install it. So I use a spring loaded center punch to put two index marks next to the bolt hole on the flywheel that is opposite to the timing hole in the engine block. I also put two index marks on the aluminum engine block that points to the flywheel bolt and the timing hole.
I add similar index marks on the flywheel guide ring and the rear nose of the crankshaft as I show later.
Remove Flywheel Bolts
I use the air impact wrench to remove the five flywheel bolts. I like doing it this way as the impact wrench does not rotate the engine.
The other technique is to insert a large blade screwdriver between the teeth on the flywheel and then use a ratchet with 19 mm socket to remove the bolts. You also use this technique to remove the clutch, which is when I took this picture.
After I remove the five flywheel bolts, I remove the ring under the bolts.
I wiggle the flywheel and pull it off the guide ring mounted on the rear nose of the crankshaft.
Remove Guide Ring
There is a “guide ring” on the rear nose of the crankshaft.
Add Index Mark To Guide Ring
Before I remove the guide ring, I add an index mark next to the same bolt hole in the guide ring as the hole on the flywheel that I added index marks next to.
Sometimes the guide ring sticks to the flywheel and comes off with the flywheel, as happened on the 1983 R100RS flywheel. But on the 1983 R80ST flywheel, the flywheel came off easily from the guide ring.
I use the Cycle Works tool to remove the guide ring off the rear nose of the crankshaft. The outer ring fits around the hub with the countersunk holes facing you. The holes align with the holes in the flywheel and the rear nose of the crankshaft.
You can heat the guide ring around the bolt holes and use pliers on the nipple to pull and wiggle the guide ring to get it off the rear crankshaft nose.
The nut is machined with a lip that will slide into the groove on the guide ring nipple. I place it on top of the outer ring and then install the three puller screws into the outer ring. The puller bolts are smaller than the threaded holes in the rear nose of the crankshaft so they bottom out in the holes. I use needle nose pliers to pull the inner nut tight in the groove of the guide ring nipple.
I tighten the three puller bolts to pull the guide ring off the flywheel.
Add Index Mark To Crankshaft Nose
After I remove the guide ring I add an index mark (two punch marks) next to the same bolt hole in the crankshaft nose as the marks on the guide ring and the flywheel so I can be sure I install the flywheel aligned with the same holes in the crankshaft it was mounted on so the ignition timing will be correct.
Guide Ring Condition
Here is what the guide ring looks like.
There is a wear ring around the circumference of the guide ring created from it rubbing on the lip of the rear main seal. Using my finger nail, I verify that the worn area is very shallow, so I can refurbish the guide ring and reuse it.
I inspect the teeth on the perimeter of the flywheel for damage from the starter motor. There are only a few teeth that have some minor dings and nicks. I’ll use a flat file to smooth them before installing the flywheel.