AJS & Matchless Owners Club

Hello,
Does anybody know the difference between the Model 20 and the Model 20B crankshaft? There is a supplemental parts list for the Model 20B bikes. One of the items in the supplemental parts list is the crankshaft, and is a different part# than what is shown in the standard parts list. The crank shaft I pulled out has worn splines in the end and needs replacement. I bought a replacement off eBay, but not sure if it's a Model 20 or 20B. It did come from the USA, so it may be a model 20b. But need more info to ID.

Thanks

I would say the crank is the same, and all to do with the size of the bore from 66mm to 69mm and the skirt on the barrels. Hope this helps. A frame number to the dating service will reveal the model.

Possibly a different balance factor due to the larger pistons hence the different part number?

Thanks for the input. I believe it is balanced differently after lots of research. Thank you for the replies.

54 Model 20B wrote:Thanks for the input. I believe it is balanced differently after lots of research. Thank you for the replies.

I'd still purchase a Mod 20/G9 crank and have it all balanced at an engineering workshop to suit. Apart from the balance factor the cranks are identical

hello,

I got the crankshaft pulled out of Model 20B. The previous owner replaced it after it broke and never got it started again, this was 30 years ago. It weighs about 5 1/2 pounds more than the stock Model 20 crankshaft I bought off eBay. I didn't realize that they are different part numbers until after I made the purchase. The ends on the crankshaft I removed from my bike are completely round. The EBay crankshaft ends are triangular. Just want verify if possible that the crankshaft I removed from the bike is a correct replacement for my Model 20B. I am now thinking about having it fixed, the splines need to be repaired. I've seen pictures of both styles of crankshafts online, and they are both listed as Model 20/30. Please see attached pics, thanks for any help.

Sorry the way the pics came out. Should be able to scroll side to side to see the end plate.

Thanks

Saves going next door to see the whole thing

Thanks you!

SPRIDDLER wrote:
Saves going next door to see the whole thing