Hello All,
I am hoping that one of you will be able to help answer a query I have.
I am trying to source a set of +0.030" piston rings for my 1947 633cc Norton Big 4, which (dare I even say it
) is attached to a Trusty 2 wheel garden tractor. So far, all my attempts at sourcing suitable rings from classic motorcycle spares retailers have proved fruitless.
I have noticed that the BSA M20/21 shares the same bore as the Norton Big 4 and when looking at pictures of M20/21 piston rings, they look remarkably similar. Would any of you kind people be able to measure a compression ring for a M20/21 and let me know how it compares with the dimensions shown in the picture at the following link - http://i1271.photobucket.com/albums/jj623/busman5/PistonRingDimensions.jpg.
If you have any problems viewing the picture or queries relating to the dimensions, please get in touch.
Sorry that this may be somewhat out of topic
email (option): seangwynn@icuknet.co.uk
Thank you for your comments. I will give Andy at Sterling Piston Engineering a try.
As for the 596cc Big 4 piston rings, I already have a set and can confirm that they don't fit. They are much thinner in cross section,0.060" (1.5mm) to be exact.
Sorry Lex, don't have any pictures of the tractor in action. It is currently undergoing restoration (have a look at the following website to see how the project is progressing - http://www.tractorbox.co.uk/forum/forum_posts.asp?TID=6279).
As for starting, it was simply a case of wrap a long leather strap around the centrifugal clutch driver and pull like hell
email (option): seangwynn@icuknet.co.uk
OK, Sean, I didn't know that! but very handy to know!
Looked at your resto blog/page, and it's interesting, some of these engines even had a huge filter on top, similar to a Vokes/Talflow.
Is there any markings on the drive side of the engine?
And sometimes there's a date inside the crankcases.
Another thing, is the broken tappet cover alu or bronze?
I think I'll stick with my own B4 Tractor!
Although the garden could do with the other variety
Cheers,
Lex
email (option): welbike@welbike.net
Cracking outfit Lex. Nice to see that it gets well used 
. I'm not one for pristine museum exhibits 
.
There are various markings stamped into the crankcase halves, but I haven't really taken much notice of them. Next time I am working on the engine, I will take some more detailed shots and e-mail them through to you if you want. Maybe you will be able to tell me what they all mean?
The broken tappet cover is Aluminium. I am going to replace it with a flat Stainless Steel plate for the time being, until I can find replacement part. I may considered having it welded back together, but am not sure if this will really be worth it.
Cheers,
Sean
email (option): seangwynn@icuknet.co.uk
Hello Lex,
Just a quick follow up post. There are no date markings on either crankcase half. The only numbers present are the part numbers. On the outside on the driven crankcase is the number 1428.
For the record, the BSA M20 piston rings were a perfect fit 
Sean
email (option): seangwynn@icuknet.co.uk