Last week I realised that the engine sprocket nut was loose. I tried to fix it but it appeared to be quite difficult as it was not clear to me how to appropriately fix / counterhold the crankshaft.
I did not find any description in the manual. I assume

Next question: Is there any info on the rubber or leather washer which is mentioned in the manual. There is no such washer mounted on my bike.

Hello Martin,

I never had that problem as it is a stationary "system" in itself and rotation between axle and sprocket is prevented by the "main shaft key".
Fastening the engine sprocket is best done by putting the gearbox in low gear and then use the resistance of the drive train to fasten the nut.

The washer between crankcase and inner chain case was rubber at the start but changed to leather at a later stage.
Many people do not have it through lack of knowledge that there was one.
They were approximately 1/16" thick and inner diameter 1 7/16, outer diameter 2 1/4". Roughly 1,5 by 35,7 x 57,3 mm. Leather works and Rubber should be oil resistant. Thickness a bit uncertain. It should be just a little thicker than the gap in mounted condition of the parts.

Cheers,

Rob

Hi Rob, thanks for your message.
I thought the appropriate way of fixing the nut of the primary sprocket is some kind of blocking the primary chain with a special tool or alternatively a piece of iron betwenn the sprocket and the clutch.
Some years ago I swapped the original 18teeth sprocket with a 19teeth version but unfortunately I forgot installation details. And obviously the nut got loose over time - too much load change behavior occured - which lead me to ask for the proper procedure.

Hello Martin,

The change to a 19 teeths sprocket should not make that much difference.
I doubt it came loose because of that change.
I have a 20 teeths sprocket there and never had any problems.
As I said, there is basically no movement between the sprocket and the axle assuming the proper thickness key is used.
If the key is not a light interference fit then it may lead to movement between the two.

Cheers,

Rob

HI Rob,
I am not an English native speaker and thus too often not sufficiently precise in technical communication. It is clear that the sprocket and the crankshaft have to be firmly "connected" due to the pressure of the nut (it presses the sprocket on the cone of the crankshaft). However, if the nut is not sufficiently tightened the sprocket can "get loose".
I assume that after the change of the sprocket the nut was not sufficiently tightened ..

Anyway, please share your experience with the 20 teeth sprocket. My impression is that even the 19 teeth sprocket is good for cross country main roads but uphill the engine lacks power to stay in 4th gear.
I am wondering if 20 teeth sprocket might be a too "long" ratio here in Southern Germany with its hills.

Martin,

Nothing wrong with your English. It is also not my native language so we might both sometimes be unclear!.
I did not want to suggest you might not have tightened it enough previous time in public.
If you did then the slight movement on the taper may have resulted in loosening of the nut inspite of the key as there would be more play in the "system".

I have been riding in France, Belgium and Luxembourg with and without camping gear on it and it goes well on most hills but indeed when it is fairly steep I do need to step back to third. I do not think that to be a problem.I am mostly riding in rather flat Netherlands!
With a second person on board it will be more problematic as going back to second gear makes you rather slow. Many cars don't like that.
With 19 teeths it is all a bit easier uphill, even with a passenger if it is not too steep.
I used to have 19 teeths for years but riding longer distances it just gives a little more speed with 20.
Have done several 800 km single or return journey trips with it and it also reduces the vibration at higher speeds a bit.

I started with 18 teeths many years ago but that was really a bit overdone and slow. Good in terrain of course but I do not doo that to much here. Not much possibilities to ride off road here in Holland anymore. It is either paved or you are not allowed to use it for fun.

cheers,

Rob