Clutch and Flywheel replacement


This document describes a process for removing and inspecting the BMW clutch and flywheel.

Work on the clutch is a fairly simple task once the gearbox has been removed.
The flywheel is slightly more complex and the use of some specialist tooling greatly assists in the job.


BMW Airhead Clutch
   
The process described here was used to address and long term oil leak coming from the join between the engine and gearbox of my R60 BMW.

Oil in this area could come from 3 possible sources.

1) The crankshaft oil seal behind the flywheel.
2) An O-ring also behind the flywheel.
3) From the oil pump cover.

To address all three possible causes the parts shown on the right were purchased.

The crank seal was of the latest 'Scraper Seal' type; as BMW have made several improvements over the years.



New Crank Seal shown on the right. Two new O-rings for flywheel and pump; and assorted stretch bolts for reassembly.


 
Three of the six clutch retaining bolts were removed and one of the holes was marked with Tipex to ensure parts would go back in the same relative location.

Then the clutch let down bolts (BMW tool 21-2-600) were inserted into these three empty holes.

With the the let down bolts providing support the three remaining original bolts were removed.

Finally - the sleeves on the three let down bolts were unscrewed in turn, to progressively relieve the clutch spring tension.

Clutch let down bolts highlighted.
   
With the clutch parts removed the flywheel was held in place with the BMW locking tool (11-2-800).

With the tool in place one flywheel bolt was removed and the hole marked with Tipex once again.

Before the remaining bolts were undone the crank end float was supported as described below. This support is important to avoid extensive remedial work.

Flywheel fitted with locking tool.
 

 
Caution. When the flywheel is removed it is possible for the crank to slide forward and if this happens bearing shims inside the rear engine cover can drop out of place. Refitting the shims is difficult without extensive strip down of the engine and failure to realise the shims have moved can lead to bigger problems. It is therefore worth taking steps to ensure the crank cannot slide forward.
   
To prevent crank movement, the engine front cover was removed and a block of wood and a ratchet strap were used. The wood was positioned as shown to press on the end of the alternator bolt shown below.
Only moderate tension of the strap is required.

Preventing crank end float

End of alternator
 
Warning. The Battery should be disconnected before removing the engine front cover. It is all too easy to cause a short on the regulator board by touching it with the cover which can cause expensive damage.
Regulator Board
  

   
With the flywheel removed The Crank shim (1), the Crank Seal (2) and the oil pump cover (3) were accessible.


Behind the flywheel
 
BMW tool 11-1-890 was mounted across the bell housing as shown to both remove and install the crank shaft seal.
Tool in place on bell housing

Tool being used to extract old crank shaft seal
 
To remove the old seal; the off centre hole was used. This took a threaded part with a foot on the end. The foot was turned to dig into the edge of the old seal. Then the threaded rod was pulled with the free spinning nut to slowly extract the seal from the housing. This bulletin from the BMW manual shows the process in more detail and also the fact that cutting the lip from the old seal can make the process easier.
 
 
The image on the right shows the bell housing cleaned up and both the crank seal and oil pump cover removed.

The oil pump had a new O-ring fitted as shown below.

All parts removed ready for a refit.

Oil pump with new O-ring Fitted
 
The new crank seal was soaked in oil for 30 minutes to soften it up.
Then it was pushed onto the insertion tool as shown.
For this bike the insertion tool had to be used with an additional spacer to ensure the correct position of the seal.

Crank seal mounted on Tool number 11-1-880 with spacer part number 11-1-881.

Using BMW tool 11-1-890 to push the seal into the engine case
 
Image showing the new seal correctly installed.

Note the orientation with the open end facing the front of the engine.

New seal correctly fitted.
 
The Flywheel was fitted with a new O-ring which was placed on the inside of the mounting boss.

The flywheel was test fitted with the old bolts to make sure everything ran true. Then the new stretch bolts were fitted and torqued up to 44lbft.

Clutch fitting was the reverse of removal with the wind down bolts being used to compress the spring and then new stretch bolts were inserted and torqued to 17lbft.

BMW tool 21-2-650 was used to centre the friction plate in the clutch assembly during this process.

Throughout reassembly any marked holes were matched up to ensure that all components went back in the same relative orientation.

Installing the clutch plate using the let down bolts and alignment tool.

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