Hi folks
Does anybody know the dimensions, specs, part num'? etc of the spacer that I believe goes between the two main bearings on the drive side of the crankcase. I cannot find this item in the parts list I have. A drawing would be perfect, thks.
Regards

Keith,

As far as I can tell, the spacer wasn't fitted to all wartime engines. It first appears in the parts book for C10217 (W45001 onwards) as part no. 4155 (Mainshaft Bearing Distance Piece)and is also included in the 1946 civilian parts book (Part no. A2/33)but it isn't in the 1938 parts book which was the same engine.

In order to fit my NOS crankcases, a used spacer that I took out of another engine needed grinding. I'm not sure if the bearings actually have any tendency to move in use. Presumably there was some concern or they wouldn't have introduced it ?

I have one here that measures .270" on the digital vernier.

Obviously, its a hardened piece. What number is your engine ? It may be best to dry-assemble with shims there in order to ascertain how thick a spacer could be fitted.

One inch.

Thanks Rik
Thats very interesting and strange! I will have to do some investigating and measuring. Things get more and more weird with these engines!

Sorry, i thought you were talking M20.

Hi Keith, my engine is 1940 and had one fitted. I didn't take any pictures of it when rebuilding my engine, but I've had a look in some boxes of bits and found one. Now I don't wish to confuse the issue here but mine is a different size to Rik's Here's some pictures and sizes, this one is probably off an OHV engine but as far as I know the bearing set up is the same.

email (option): horror@blueyonder.co.uk

Many thks Horror
All info gratefully received! The pictures really help.

I can't say with certainty which engine my spacer came out of. However, for any given year, OHV and SV crank spacing should be the same. Any difference is likely to be between the open valves, enclosed valves and circular follower engines.

I've photographed the spacer that I have. Don't take the measurements as gospel as it was a real fiddle trying to hold things as well as the camera.





ID seems to be 2" - There is an odd parallax effect in this photo.



A trader in Australia has had them listed but is out of stock. However, his illustration is different again.

http://www.bmhstore.bmh.com.au/index.php?main_page=product_info&products_id=1331

What are the holes for?

I think they are to allow oil to the outside bearing. There is also a hole after the outside bearing that let's excess oil out. I don't know why it needs this, unless I'm wrong about its function. But when my bike wet sumped it leaked down the crank case there.

email (option): horror@blueyonder.co.uk