Vintage BMW Motorcycle Owners

Still grappling with that crank. Yes I have been off servicing our Landcruiser and other tasks. Good to come back with fresh eyes.

Finally got that front web sitting acceptably parallel with the centre web. Learnt a few things there.
In the process tweaked my data collection sheet again. Not much of a change but refinement.
Here it is for those who find it interesting.


Mal

well the crank is now within specs. A lot of lessons in that exercise.

Now I have to sort out the flywheel.
I have the correct slightly lighter R69s flywheel to fit against a new crank.
So more runout questions.

So now the crank trueing stand gets new tops to cope with the extra weight of the flywheel.

Mal

Nice job. It's always a pleasure to see old engines/bikes come back to life. Keep up the good work and keep posting photos of the progress. Thanks

The test with the flywheel installed on the bench is probably not worth much. The test will be after installation in the case and then truing the flywheel to that. A lot of trial and error may be necessary, but sometimes they come right in.

Dave

Daves79x wrote: ↑

Wed Jan 06, 2021 11:53 am

The test with the flywheel installed on the bench is probably not worth much. The test will be after installation in the case and then truing the flywheel to that. A lot of trial and error may be necessary, but sometimes they come right in.

Dave

Dave

You are probably right.

In the past when reassembling a flywheel to a crank where they had seen service as a pair I have done what you recommend.
However this crank has never been matched to this flywheel and I dont know how well they will play together.

What was in my mind was that if I need to use some valve grinding paste to get this flywheel to seat properly on this crank then I would prefer to do that before I have the crank fitted into the crankcase. That way I can been more confident of keeping everything uncontaminated.

We will see what we see, I guess.

Thanks for taking the time to comment.


Mal

Well delays, delays, delays......

Today I thought I would check out the clearance between the back of the flywheel and the rear main engine bearing.
So out with the new oil slingers. Poor fit. mmmmmmmm.
The problem is that the way the reproduction slingers have been pressed the part that is meant to snug into the crankshaft won't sit in correctly.

So I made a press tool and tweaked the slinger and now I have a perfect fit.
I did made a video clip of the process but was unable to upload video to this page.

Mal

Well the flywheel is sorted. I did put a speedie sleeve on just to make the oil seal surface 100% I did give the bench a clean up ready for the engine assembly steps.

Now I am measuring up all the clearances involved in fitting the new crank into the crankcase.
Of course one can just look in the manual and see, place 3.6mm front spacer and 2mm rear spacer........ assemble.
However past experience tells me that one does not want the front slinger to rub on the front bearing carrier or the rear oil slinger to touch the rear bearing carrier.
So I draw up a scale drawing with the actual measurements and see what dimension spacers I need and also if the front bearing carrier needs tweaking.
Also this allows one to ensure the conrods sit as equally centred on the bores as possible given the crank assembly. In this case the conrods are sitting very close to spot on.
Next step is to calculate out the front shim thickness required.

Well the 3.6mm spacer looks good for the centering of the conrods in the bores.
Just need to look at the oil slinger clearance.
and of course need to confirm the rear bear carrier will sit well with the rear oil slinger if I use the 2mm spacer.

The stock spacers should work the vast majority of the time. There is no guarantee that the front or rear slinger won't rub a bit. All that's required in that case is to reach in and slightly tweak the slinger away from the carrier. It's what most everyone I know does and it worked for me as well.

Dave

The real fun is yet to come. Do yourself a favor and heat the case in the oven to at least 300 degrees F. Obviously freeze the crank overnight. The crank will fall in. And still retain enough heat so the rear bearing race does not stick when drawing the assembly forward into the front carrier.

Dave