Seized Engine?

[Crossrodes]

I recently took my clutch and flywheel out of my '79 to replace a seal and gasket.  Today I was putting it back together.  After installing the flywheel I found that I could not turn the engine over.  

Before I took the flywheel out I was advised to block the engine which I did.  I was told of some catastrophic consequences if the crank moved forward, so I blocked the crank with a cut off Allen key inserted into the alternator which was pushing against the front cover.  

What I'm wondering is if I did not block the crank enough and that is the cause of my seizure.  Exactly what does happen if one fails to block the crank properly?

[Bob_Roller]

There's a thrust washer that if it gets dislodges, will lock up the crankshaft .

You need to remove the cylinders then remove the flywheel again, push the crankshaft forward to gain access to the crankshaft thrust washer through the cylinder holes in the crankcase .

It's hung on two pins cast into the crankcase halves .

I believe one of members here, Trolle did this method a few years back, maybe he can give you some pointers on what to do .

[Mike V]

Crossroads,

http://www.airheads.org/content/view/157/49/

More info on this in Snowbum's web site...
http://bmwmotorcycletech.info/clutch.htm

Good luck with this, let us know what you find,

[Red_Hen]

Their is a thread on the BMW MOA Forum called:

Blocking the crankshaft. Why?

http://www.bmwmoa.org/forum/showthread.php?p=594358

You may have to be a member to view - I emailed the thread to myself so if you can't read it and need me to send it to you, just send me a PM or kentuvman@gmail.com

[Crossrodes]

Thanks for the link Ken.  Unfortunately the description of what happens when the crank is not blocked is exactly what happened with mine.  Now I get to have another new experience in replacing this shim.  

[donbmw]

I would pull the flywheel off again and check the thrush washer  behind the flywheel. I could have come off the pins that hold it in place. I would check this before going into the engine for the shim on the inside. I had this happen to me this winter when going back together after changing the shaft seal and oil pump oring. I didnot notice that it was not in position when I put the flywheel back in.                                                            

[Crossrodes]

I'll check that Don.

[Crossrodes]

OK, as Donbmw suggested I pulled the flywheel again and discovered that the pins did not line up with the thrust washer.  So I oriented the engine so that the thrust washer would line up with the pins without moving while I put the flywheel back on.  (I had noticed that as I loosened off the flywheel during the removal process that the crank would turn again).  I re-installed the flywheel and tightened her down a little...no joy, the crank would not move.  So I removed the flywheel again to check that the thrust washer was still on the pins...it was.

So does this indicate that shim or inside thrust washer is shot for sure?  I looked at the parts diagram to see where these pins are attached and what, if anything they, pass through.  Unfortunately the parts diagrams don't have enough detail to help me.  

[Bob_Roller]

The pins are part of the engine case castings  .

Usually when the thrust washer gets dislodged and then the flywheel reinstalled and tightened down, it bends the washer, it's a relatively soft material .

So you really need to replace it .

[Crossrodes]

Thanks Bob.  

Your answer raises another question... I have been told that to replace this thrust bearing I will need to pull the pan and cylinders/pistons.  But if these pins are part of the engine castings would they not be external to the casting and would not the correct thing to do be to remove the crank seal again and get at the thrust washer that way without going inside  the engine?

[Bob_Roller]

The thrust washer is larger than the hole in the rear of the engine case, so you can't access it from the backside of the engine .

Send one of our members here a PM, his name is trolle, he had this happen about two years ago, but I can't find his postings doing a search .

I'm sure he can give you a good description of what needs to be done .

[Crossrodes]

Thanks Bob.  I looked for his posting also and could not find it.  I have sent a PM.