My first bike was an M21 back in'71 when I was still at Boarding school. I later got another at College in 75. They both cost £30.
It wasn't till I got a third one 10 years ago that I discovered this part, and then only whilst browsing Draganfly parts files...
I've belatedly come to the realisation that I could have saved myself a great deal of time and money if I'd always had one. The second I had to let go after being chased by a police minivan in Mid Wales. It's spark was so weak I often had to close the gap right down and then at the top of a hill open it again. I used to start it by spinning the engine up and letting out the decompressor. On the motorway I drafted coaches. It was a typically worn 70s bike. Most of us were getting round on 50's relics. Anything with girders was looked upon as being out of the Ark.....

Thanks! Makes sense.
More questions will follow probably ;)

email (option): info@erfgoed40-45.nl

Meanwhile I am much further with my project

But I have a new question
What needs to be in the two holes below the timing gears. The two holes in the bottom between the closing screws.

I think the manual says a retraction screw for the oilpump retainer but does this need to be there or do you remove this before closing?

Next to it looks to me like a spring and Ballbearing but I could be wrong.

Hope on some help from you guys.

email (option): Info@erfgoed40-45.nl

https://ibb.co/4MQ92cG

email (option): info@erfgoed40-45.nl

The hole which contains the oil pump retainer stays just as it is. You need a 1/4 x BSC screw/bolt to remove it before removing the oil pump drive spindle. The retainer is just a push fit in that hole.

The other hole is for the oil feed relief valve which is a ball and spring in the timing cover. Ron

email (option): ronpier@talk21.com

Thank you very much!

email (option): Info@erfgoed40-45.nl