Engine dismantling questions

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Engine dismantling questions

Postby clanger9 » Mon Oct 02, 2017 8:11 pm

I've decided to rebuild my engine over this winter on account of a rapidly worsening "death clatter" from the bottom end.
So far so good on stripping it down, but I've hit a few snags:

1) How do you undo the large screw that covers the end of the oil pump hole? The manual just says "remove the screwed plug". It appears to be stuck. Do I just need a bloody big screwdriver?

2) How do you safely undo the timing pinion nut? It seems to be very tight and I can't figure out how to lock the crankshaft.

3) Can anyone lend me a timing pinion extractor, or point me to a source? These seem to be unavailable from club spares at the moment.

Hopefully once I've got it stripped down I can find the cause of the noise. The engine appears serviceable, but there is a lot of lift on the timing side crank bush, so it's going to have to come to bits one way or another...
1966 AJS Model 14 250 CSR "cafe racer"
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Re: Engine dismantling questions

Postby 56G80S » Mon Oct 02, 2017 8:51 pm

Long time since I had my 1966 14 CSR although I really liked it.

1) don't recall clearly but thought mine had an Allen key hole or I may imagine that

20 Daft to say but I assume that the timing pinion, like the 350 & 500 heavyweights, is left hand thread? Only had the G80S one off once (to replace it) and used a large ring spanner and clipped it with a soft mallet. Of course, on G80S the timing side axle will come out through the bush.

3) As I'm a bodger I have used soft metal wedges!

I am planning a strip of the G80S this winter in order to carry out a similar exercise on the timing side bushh - hope all goes well for you.

The one I sold also had a bottom end knock - I informed the purchaser who after a test ride said he couldn't hear it. I told him it was there and strip engine once home, not give it to his 17 year old son and that's why the price was low. 3 - 4 months later he 'phoned to abuse me as drive side bearing loose in housing was actually the cause and had wrecked the crankcase half. When asked if he'd stripped it as recommended - NO. Bet he still calls me names.

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Re: Engine dismantling questions

Postby Rob Harknett » Mon Oct 02, 2017 8:59 pm


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Re: Engine dismantling questions

Postby clanger9 » Mon Oct 02, 2017 9:02 pm

The oil pump cover looks like this. A normal hex key (like they used on the oil filter) would have been much easier to undo!

IMG_1683 (1).jpg


I'm certain the pinion is right-hand thread (at least that's what it says in the manual); I guess I can chock the crank pin with a suitable piece of wood?
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Re: Engine dismantling questions

Postby clanger9 » Mon Oct 02, 2017 9:07 pm

Rob Harknett wrote:http://archives.jampot.dk/book/Workshop_manuals/1957-1966_Singles_F.W.NEILL.pdfIs this the book you are looking at?


No, I've got the "red" factory manual, but the instructions in the F Neill manual appear to be similar.
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Re: Engine dismantling questions

Postby alanengineer » Mon Oct 02, 2017 9:13 pm

3 Timing pinion extractor. Yes you need one or you will do damage or not do the job at all. You have to be really nice to people for them to lend one of them. Mines on a long piece of string, wont reach to Chester.

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Re: Engine dismantling questions

Postby Ozmadman » Tue Oct 03, 2017 12:34 am

clanger9 wrote:I've decided to rebuild my engine over this winter on account of a rapidly worsening "death clatter" from the bottom end.
So far so good on stripping it down, but I've hit a few snags:

1) How do you undo the large screw that covers the end of the oil pump hole? The manual just says "remove the screwed plug". It appears to be stuck. Do I just need a bloody big screwdriver?

2) How do you safely undo the timing pinion nut? It seems to be very tight and I can't figure out how to lock the crankshaft.

3) Can anyone lend me a timing pinion extractor, or point me to a source? These seem to be unavailable from club spares at the moment.

Hopefully once I've got it stripped down I can find the cause of the noise. The engine appears serviceable, but there is a lot of lift on the timing side crank bush, so it's going to have to come to bits one way or another...


1) I just used a hefty screwdriver which has a hex on the shaft for a spanner to fit on

2) Don't remember this being a LH thread as has been mentioned? Mine responded to a sharp whack on the socket handle

My knock was from the timing side bush but I changed both LH crank bearings as well and got and engineer to fit and line ream the bush to fit the crank. I couldn't detect and up down movement in the big end bearing at all so it went back as it was and is fine. Also, once apart check the breather stator fit where it fits between the two bearings, there are 3 different types of fitting ( the early one like mine where the breather tube is a push fit in the stator and is threaded in the casing, the intermediate one where the breather tube is threaded into the stator and the later one where the stator is held in place by a bolt in the casing and there is no breather tube at all just a drilling in the casing) The early one causes problems as a small amount of play develops between the tube and stator which causes the stator to rattle around making the wear worse until it sounds like a bearing failure. see video clip


https://youtu.be/xux_7OUzkt4
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Re: Engine dismantling questions

Postby clanger9 » Tue Oct 03, 2017 5:56 am

Thanks, Paul. The pinion nut is most definitely RIGHT HAND thread on the Lightweights.
My timed breather appears to be intact - I suspect the rattle is just from bottom-end wear (there is slight lift on the big end).

It looks like I might have to weld up an extractor tool...
1966 AJS Model 14 250 CSR "cafe racer"
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Re: Engine dismantling questions

Postby clanger9 » Tue Oct 03, 2017 4:44 pm

Sorted! There's a conveniently-placed hole in the crankcase to allow the flywheel to be held securely with a dowel.

IMG_1685.jpg


I even managed to get the pinion off. Purists - don't try this at home, but a standard 22mm brass pipe fitting screws straight on (finger tight, obviously). A thin-bladed puller brought it straight off. Clearly this method will only work if the pinion isn't stuck fast.

IMG_1686.jpg


The timing side bush is properly worn - over 30 thou of clearance! That would explain some of the funny noises.
Now on to the oil pump screw...
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Re: Engine dismantling questions

Postby Ozmadman » Tue Oct 03, 2017 9:31 pm

Weird??!! mine hasn't got that hole. Looks like it has been drilled out by somebody?? On a second look, maybe that is correct as mine has an oil return hole back to the tank if you look carefully about opposite the B on that casting whereas yours doesn't have that hole so your oil flow would drop back into the crank area when the cam and followers area fills up with oil.
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