AJS & Matchless Owners Club

I have a few sets of crankcase halves and I have studied them to see if they are marked in pairs. I did not notice anything. Does anyone know how AMC marked cases to indicate pairs?
Most BSA cases I have seen are stamped with the same (usually 3) number each side on a through bolt boss.
Trevor

Not sure what years you may be referring to. Most Wolverhampton AJS crank cases were matched. The AJS up to about 1930. When the crank cases were machined to match, an identical number was stamped on the top, at the rear of the barrel, on each half.

Sorry, I do mean all twin crankcases from 1955 to the end of the line.

I have checked my 1960 parts book and AMC listed each crankcase half under a separate part number. That means they were confident enough in their machining process that you could buy one half and it would fit to the 'other' half. No other manufacturer that I know of would do that. You had to buy a 'matched' pair of crankcases halves.

That's a very good question Trevor.
In all the twin crankcases which I have seen, numbers are stamped inside each half but none of mine have the same number in both halves.
I always assumed that they must have been matched at the factory - otherwise what would be the point in stamping them?
Conclusion - either I haven't cracked the code yet, or all mine are unmatched halves.
It would useful to hear from anyone who has a pair with identical nos. in each half.

I have never heard of crank cases having a different number stamped inside. Surely any numbers would be cast, and all the same for the particular casting. So left and right would have a different casting number. On a single, only a drive side casting would have its own unique number showing year and model, stamped on the outside. In the late 30's you could find a coil ignition model number stamped on drive side. The timing side being that for mag. ignition. Post war you could find a drive side stamped for an AJS year / model, The timing side badged Matchless. This seems to be common practise, without any machining to match required.

Not noticed any marking on crankcase halves but have seen 3 numbers stamped on single timing side crankcase and matching ones on the timing gear cover. I think the point is Rob that rather than the mrks being cast, once a set of cases had been bored the operator may stamp them to ensure the matching halves stayed together. Having said that I have built up a couple of single engines with mismatched halves and even more with missmatched crankcase and timing gear cover and they do not seem to have been a problem.

TrevorCSR wrote:I have checked my 1960 parts book and AMC listed each crankcase half under a separate part number. That means they were confident enough in their machining process that you could buy one half and it would fit to the 'other' half. No other manufacturer that I know of would do that. You had to buy a 'matched' pair of crankcases halves.

Trevor I have a feeling that I read somewhere in the spares or owners books from AMC that if buying a single crankcase you need to send the other for them to check the match, but it may just be my imagination.

If you have mismatched single halves, you can normally feel at the top, where the barrel fits into is not the same, i always assumed the twins would be the same. But im assured by others the halves were machined to such high quality, that this didnt happen.

The twins have separate barrels, with one on each crankcase half, so the mismatch is not critical in that respect.

Rob C

The barrel face is the least important machine face. What about roller main bearing alignment, plus of course the centre web. Two sets of camshaft bushes that should be line reamed.