Not easy Kai! As Leon said "clockwise in and clockwise out" I have an M20 speedo drive in my hand, but can't see any part number. The only other one that I've found 'so far' that you can use, is off a post war Royal Enfield Flying Flea, and you have to drill the spindle hole bigger.
If ever I see these drives at jumbles, I always pick them up and check the rotation. Unfortunately they are nearly always anti clock
Ron
email (option): ronpier@talk21.com
Dave, I'm afraid the Patent Number isn't an indicator of the rotation direction. I was stitched-up by an eBay seller for a pricey speedo gearbox ages ago that looked identical and I was green enough to believe him when he said it suited an M20. Time passed and I pulled it out when I had finally got to the point of fitting it and was dismayed to find it rotated the other direction.
These two pictured look very similar and both have the same Patent Number but are opposite in rotation (the one on the left is the one that has the correct rotation for the M20.
Kai, this is what you need to look for as mentioned by Ron earlier. A word of advice - don't walk past those rusty, worthless looking wheels, one of them might well have a working, correct rotation speedo gearbox.
email (option): rays54@hotmail.com
Ray, thanks for your reply. I have an idea about the Pat Number. Maybe, the number is just for the housing, something like a universal item, then different internals are installed for anti or counterclockwise rotation? That is only an idea.
That must have been a bit of a sickener getting stiched up? I have bought parts before and not used them for ages, only to find out that there are not correct.
Ray my speedo drive looks like the one one on the right. It's is correct and works. I seared the screws, Dave Plumb sorted it for me
Thanks Dave.
Dave
email (option): jeepfinger@blueyonder.co.uk