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R51/3 – kick-start won't turn engine

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Micha
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R51/3 – kick-start won't turn engine

Post by Micha »

After restoring the gearbox and installing the clutch, I attached the tyranny to the engine, and it went smooth on. The problem is that I'm unable to turn the engine as the kickstart is stuck (it will turn freely while not mounted).
As you can see, the clutch/flywheel area went through a trauma in the past while owned by PO's sometime (blue arrow).
The bolts that are marked with the red arrows are my installation (old ones where trash) and I suspect that they are the problem as they protrude above the surface too much.
Would like to hear your opinion, or shell I search somewhere else?
Thanks a lot - Michael
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Michael Steinmann
R51/3 1952
Engine Nr. 529466

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wa1nca
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Re: R51/3 – kick-start won't turn engine

Post by wa1nca »

Very likely they are hitting the clutch when installed
Salis has them
https://bmwclassicmotorcycles.com/index ... -head.html
Or if the ones you have are beveled can you take a larger drill bit and open up the top of the holes so they seat flush with the case
Tommy
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

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Micha
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Re: R51/3 – kick-start won't turn engine

Post by Micha »

Thanks Tommy.
Do you happened to know if the clutch bolts are with the same 60°at their cone?
https://bmwclassicmotorcycles.com/index ... screw.html
I have some of them spare and can cut them to size.
It's not mentioned at Salis nor in the Auxiliary catalogue.
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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wa1nca
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Re: R51/3 – kick-start won't turn engine

Post by wa1nca »

Not sure if they are the same pitch but mostly are
and the bevel is the same at 60 degrees
If they are then you can shorting the ones you have to 15mm
Tommy
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

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Micha
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Re: R51/3 Matching the tranny to the engine - strange phenomena

Post by Micha »

Further to this issue and after replacing the suspected bolts, I would like to summarize the overall picture:

Engine overhauled including the crankshaft. The closed engine rotates well.
Main new items assembled from the side of the engine:
Clutch pressure plate, all the springs, clutch plate (special tool was used to center assembly).

Transmission overhauled including of course all the oil retainers and bearings.
On the bench the transmission performs smoothly and the kickstarter turns well. With an external voltage connection, the NEUTRAL light unit also works great.
Main new items assembled from the side of the tranny:
Complete pushrode Assembly including thrust piece & bearing.

While attaching to the engine, I keep a close watch on the gearshaft so it combains into the engine/flywheel area.
I use slight rotation play via the driveshaft output on the tranny.
The pushrod also gets smooth inside, finding its place in the square hole.

Then when all is combined, it is stucked. Completly, not one mm of play.
As soon as I withdraw the tranny back - while still resting on the studs - all gets loose again, turning freely.

ANY HELP WILL BE MUCH APPRECIATED... :?
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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caker
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Re: R51/3 – kick-start won't turn engine

Post by caker »

Hmm. Wrong thickness clutch plate?

I ran into this with my R68 restoration - I bought a 9mm plate as a replacement (R68 used a variety of thicknesses over the years of production), and had to re-order a thinner, 7mm plate - which I think is also correct for R51/3? It's been many years, but I believe I discovered this while assembling everything - the same thing happened: when together, the motor and trans and everything wouldn't turn over.

-Chris

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Re: R51/3 – kick-start won't turn engine

Post by Micha »

Morning Chris,
That was my first thought, but I know I bought the right clutch from Mark Huggett, a 7 mm item.
Clutch plate was also inspected before assembly, both items were compared to the old ones.
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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bm68andreas
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Re: R51/3 – kick-start won't turn engine

Post by bm68andreas »

try to unscrew the trany a little bit, i mean just 2 turns each nut and the bolt..
[iKONTOGIANIS][/i]

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Re: R51/3 – kick-start won't turn engine

Post by Micha »

Hi bm68, thanks for the tip, I tried it already.
I worked on it all night. Added some pictures.
I now realize I did a bit of a sloppy job. I probably rushed:
Here are the original plate and the new one I installed and they are not the same...
New one on the right. Flatter.
Could it be that the old one deformed itself over the years?
You can definitely see a difference in height due to the curvature of the old plate.
The new one is a modern replica "made according to the originl drawing".
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Michael Steinmann
R51/3 1952
Engine Nr. 529466

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Re: R51/3 – kick-start won't turn engine

Post by Jim D 5112 »

Take some machinist layout fluid bluing and paint the areas that may be hitting or binding. Then put the transmission back in. Tighten up the mounting bolts up slowly awhile rotating the motor or transmission until you feel it starting to hit or bind. Then take the transmission back out and look for the areas that may be hitting. The bluing should show anything that is making contact that is causing the problem. You could also remove the clutch assembly from the flywheel and put the transmission back in and see if it still binds. Layout fluid can be removed with a rag and acetone. But I would not paint the aluminum casting it may be harder to remove and would probably take longer than a smooth surface.
Last edited by Jim D 5112 on Fri Oct 09, 2020 7:58 pm, edited 1 time in total.

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