Hi Luke. I'm sure Ian Wright will be along later as he is far more familiar with the different models and periods of change. But many of us have fitted an M21 crankshaft into our M20 crankcases and I'm not aware that the KM cases are different. Previous cases (1937 or 38??) were narrower with only one bearing on the timing side.....But that wont affect you.
Presumably your outer drive side main bearing is all the way in, past the circlip groove? You should be able to fit each case half in turn to see which side is not meeting the middle of the conrod.
Regarding the numbers that are cast into parts. (like the conrod which is one digit out from the parts list) These are the foundry numbers before any machining or assembly after which the part number becomes that in the lists. Ron
At first glance I thought I had an early style HM from 37/38 that was perhaps a leftover in '39.
after inspecting the differences I ruled that out right away. I thought, just my luck. LOL
I'm going to check some precise measurements this weekend.
And look for burrs or wear on a shaft that may be hanging me up.
I will check the race fitment, as you suggested too.
Thank you.
We shall see if there is a mechanical issue, over a parts issue.
Perhaps more will elude to my difficulty.
I think I may have found the issue...
The outer most drive-side bearing is kind of gnarly on the inside diameter.
I flipped the case around and that bearing will not go on the appropriate shaft.
Tomorrow I will drive out the roller bearing race, and ball bearing and get a closer look.
The retainer clip was missing as well, but the bearing seemed to be seated correctly with the thin shim behind it.
I ll keep everyone posted.
Thanks.
Those bearing circlips are a nightmare so I bought the type with the little loops on each end. My bearing supplier managed to find some with the correct thickness which I think were from USA.
AFAIK the only difference between early & late cases was the strengthening plate for the cams
And the placement
Early cases had the cams closer together and the cases end to crack around them'
Am yet to see a clean one
They cured this by widening the space between the cams wih a bigger pinion and of course he carrier plate.
Not sure when they did it
The M23 is the early narrow case .
