AJS & Matchless Owners Club

I HAVE RECENTLY ACQUIRED A PAIR OF CRANKCASES WHICH I HOPE ARE FOR A SHORT STROKE 500 AJS. THE NUMBER IS 57/18 2630CS. AM I RIGHT BEFORE STARTING THE SEARCH FOR THE REST OF AN ENGINE?

I have a 1956 s/s engine the number being 56/G80 xxxxxetc CS, I would have thought apart from the numbering being AJS on yours that they were identical kind regards

I am sure 1957 500 model 18CS was long stroke at 93 mm. ??? You can check stroke in the sale cat specifications.

Rob,
The 57 CS (and 56 for that matter) would have been a Short Stroke.
I previously had a couple of 56 Short Strokes (one Matchless one AJS) with engine numbers circa 300 before the quoted number so it would look to be in the correct range.
John

Don't know these engine well John, if 56/57 are 93 mm stroke, that's the same as 40's models I thought were long stroke. Aha 55 56 & 57 CS models 82.5 stroke just looked.

Rob where on earth did you get the 93mm dimension from? No dimensions were quoted in the original posting merely an engine number/model number. By adding what you did merely confuses the matter.

The person was concerned about the stroke Rob. Long or short are determined by the dimensions. If you check specifications , for stroke it does not state long or short. So you need to refer to the dimensions given. For 55/57 STD 500 single engines seem to be 93 mm just the CS engines 82.5 mm. This confirms the question the CS engine is a short stroke engine. Or am I wrong in thinking a 93 mm stoke is long and 82.5 mm short.

Rob Harknett wrote:The person was concerned about the stroke Rob. Long or short are determined by the dimensions. If you check specifications , for stroke it does not state long or short. So you need to refer to the dimensions given. For 55/57 STD 500 single engines seem to be 93 mm just the CS engines 82.5 mm. This confirms the question the CS engine is a short stroke engine. Or am I wrong in thinking a 93 mm stoke is long and 82.5 mm short.

Methinks you're confusing yourself Rob. The post was asking if the cases were for a short stroke engine, well the answer is yes because they didn't produce a long stroke 500 CS after 1955. From 56 onwards all 500 CS models were shortstroke! Only the 350 was retained in both formats long and short but the cases are stamped for a Model 18 CS which is 500cc. Simples really!

I am not confusing myself Rob. I checked literature which should be correct. Instead of just saying yes, I confirmed how yes was arrived at. Since time began engine specification's stated bore & stroke dimensions. So all you need to do if you need to know if stoke is longer or shorter in one and another. You can just check the engine specifications concerned. c.c. also differs. 498 and 497. Which is which, no need to ask, answer is where you checked the stroke dimensions.
I have however made a typo 82.5 mm should read 85.5 mm.

You should be able to identify the timing side crankcase as a short stroke if it has the provision for the timing side bearing... the long stroke CS models didn't have that bearing.