AJS & Matchless Owners Club

During my "exciting" first run out today, I noticed a bit more rumble and grumble from the primary drive than there ought to be.

I've had a look to investigate and here's what I've found:

• There is noticeable end float on the crank, even though the end nut is done up tight. Any end float is supposed to disappear completely with the nut tight, yes?
• The crank sprocket looks to be brand new.
  
• There are a couple of shims between the crank sprocket and the main bearing, however...
• The sprocket doesn't seem to go fully "home" on the crankshaft - instead, it seems to get stuck on a slight step as the splines get shallower towards the main bearing.
  
• There is a strange wear pattern on the back of the alternator rotor - as if it's fouling on the chain.
  

What could be wrong here? Chief suspect is the new crank sprocket...

- Should there be a chamfer on the sprocket splines to enable it to go fully home?
- Should there be some sort of spacer between the sprocket and the alternator rotor? I can't see anything on the engine diagram.

Apologies for all the questions. As some of you may know, my bike has a rather "uncertain" history and it's sometimes difficult to sort out the normal issues from bodger-induced ones...

Paul

Looking at the exploded diagram you may be missing part number 041091 which looks like a spacer, I think your sprocket might have been put on back to front to compensate hence the chain rubbing on the rotor, hopefully some one who knows will be able to provide the dimensions of the spacer.

041091 looks like a spacer but it does not seem to be listed in a parts list ???? There is a spacer to watch out for, and probably 041091

Great info, thanks! I don't think it's possible to put the sprocket on back to front, but a missing spacer between the sprocket and the rotor would definitely explain the fouling of the chain.
I suspect the previous owner replaced the sprocket without checking the endfloat. I think I can fix this with another shim (of approx 10 thou).

Duncan asked the all-important question: does anyone know what the thickness is of the mystery 041091 spacer? It's not available from the spares scheme, so I'll probably have to make something up...

[edit]
I take that back - I think Duncan is right: I just had another look and - without the all-important 041091 spacer - it *is* possible to fit the sprocket the wrong way round! That would explain both the fouling on the rotor and also the crank endfloat.

Looks like I need a spacer. I will have a rummage through the box o' bits, just in case something turns up. Failing that, does anyone have a spare spacer lying around?

Having the sprocket the wrong way round and/or minus the spacer, would surely put the sprockets/chain out of line also
earlier machines had a similar little spacer. Prewar 37' ish AJS did. Not checked if it was used post war. If it was and available it may fit the shaft. Perhaps it will be too thick, so could be ground down to suit. You should be able to discover the thickness, by putting washers on the shaft, when the sprockets line up, measure the washers used thickness.

I think the spacer you are looking for is 023066, in stock at Kettering.

This is a 250 lightweight I think so with the rotor and sprocket removed there should be about .040" minimum endfloat in the crankshaft, when you fit the sprocket and rotor and tighten the nut the endfloat will vanish.
If I am honest I can't remember a spacer being fitted to engines I have messed with, there is a sprocket shim 044058 .010" and 041091 number but description can't be found.
Measure the end float with sprocket and rotor on and get a spacer made .010" longer, and hope there is nothing untoward inside, I will have a look in my bits box see if there's any likely looking spacers, of course everything is filed by part number and listed .............a regular stock check also helps

Colin

The part 041091 is shown and listed on exploded engine drawings, mentioned in manuals to look out for it when removing sprocket. But, does not appear to be listed in the parts list. Errors were made in factory literature, often an errata was later issued and stuck in books or just loose. So everything is not always listed or perhaps not correct in parts books etc.

Exactly what I had, basically you have the sprocket on the wrong way round which is causing the primary chain to rub on the rotor. If you put it on the correct way round it will go fully home. The end of the sprocket showing in your picture should be facing you when the sprocket is on the shaft. There should be about 20 thou end float without the sprocket/rotor on which will go when all is tightened up. I had two thin shims that were behind the nut instead of the sprocket. I would have sworn that the sprocket was the correct way round but I was proved wrong. When round the correct way it looks like the sprocket would hit the casing but it won't, use any shims you have between the sprocket and bearing to line up the primary chain then put the rotor on, then the large washer and then the nut. The end float should go and the primary chain will clear the rotor. There is no distance piece behind the sprocket only shims as required

Paul confirms what I thought (bloody memory) no need for me to rummage then, I will go for a ride seeing the sun is shining