47/G80L engine.

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Yak
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47/G80L engine.

Post by Yak »

I have just aquired engine 47/G80L 3529 for restoring (eventually). The word SPECIAL is stamped below the engine No., quite neatly but not as deep so am not sure if this is of any significance. My main puzzle is that it has only got the single start timing axle with bush and roller bearing, so am wondering if the cases might be a mismatch. My 47G3L has the double start axle and stepped timing side bush. the '47 spares book pictures the single start assembly so it is a little confusing (for me). The cases are flush at the top and at a couple of points points around the joint a slight ridge of unevenness can be felt. Mind you I split the crankcases and have loosely reassembled them after a good clean. My books say double start pump was introduced "from" 1947. Could it be that it came in "during" 1947. I also got a pre-monobloc carb. It is stamped 276 DR MAT on the manifold and has no air holes in the mixing chamber. It does have a slot cut into the bottom of the intake. Would I be correct in thinking this would be from a WD G3l.

Thanks Ray.
Yak
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Re: 47/G80L engine.

Post by Yak »

Greetings. As I am planning to rebuild the above engine I have resurrected my own post with added queries. Does the timing side crankcase differ between 2 start and single start axle arrangements, that is to say will a two start timing side axle and appropriate bush to replace roller bearing fit, without modification, into the crankcase? I have searched the forums and found plenty of info about oil pumps and their differences but not so much on crankcases.
Thanks
Ray.
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saltbox alf
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Re: 47/G80L engine.

Post by saltbox alf »

I think you will find the difference is with the flywheel timing side axle for single start and double start threads.
there was a good article in a 'Jampot mag' a couple of years ago, re- the same difference and it covered oil pumps etc.
Allons-y, amis de Matchless et AJS
Yak
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Re: 47/G80L engine.

Post by Yak »

Thanks Saltbox alf. My intention is to replace drive and timing shafts and main and big end bearings. I do not have a oil pump for it as yet. Am not convinced I have a 1947 timing side case but have just read that the guide pin hole was enlarged in 1948 so will check this. I have no history of the motor so have to spend a dollar or two getting things true and correct.
Ray.
Yak
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Re: 47/G80L engine.

Post by Yak »

Hi.
Just in the early stages of making a shopping list. I have found a supplier of the timing side roller bearing and race (NOS) at a pretty good price. Was wondering why the design team at the time changed to a bush in the first place, and whether this is the way to go bearing in mind i would like to fit the 2 start oil pump set up.
Thanks
Ray
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clive
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Re: 47/G80L engine.

Post by clive »

Yak a look at the 1947 Matchless parts list seems to answer your questions. It lists std-650 "used when no roller bearing is fitted" so presumably the change occurred at some time in the year the list covers. I am guessing that std-650 was a plain bush, probably phosphor bronze, and was likely to be much cheaper than a roller bearing. The other alternative is that post-war the bearing was simply not available. Well done in finding a supplier of NOS though.
clive
if it ain't broke don't fix
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Rob Harknett
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Re: 47/G80L engine.

Post by Rob Harknett »

You could had found the part a lot closer than you think. Right here in club spares.
You will do well, if you have a pre 1952 machine, to convert the part number required to the new part number, STD 650 would be 000650. Search that in club spares and you will see even a later pt no. for 000650 is 015780.
Once again a little reminder, 3 years ago I made an excell file listing what parts club spares stocked at the time, showing old and new pt. no's, It may now be a bit out of date, due to items in/out of stock or new items in stock. The list has never been published, its up to the club committee I guess, if the file should be published. At present the file is password protected which I will remove if the file is to be published.
Yak
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Re: 47/G80L engine.

Post by Yak »

Hello back again with some more questions.
Have had bottom end restored with all shafts, bearings and bushes replaced with new. Consequently am out of money so just doing a little research. I have a spare rigid frame and want to fit the motor in it to see how it all lines up. The engine plates I have fit nicely on the engine but they are different, with one having the dynamo locating notch at the top the other to the rear. The RHS plate has a couple of extra holes towards the rear, near the slots for primary chain adjustment, but the rest line up perfectly. Cannot find a decent picture of the 500 engine plates other than the diagrams showing spacers required thro different years and models.The shape of mine are quite different to these drawings, but I am guessing (hoping) they are rough sketches.
The '47 parts list, Part No. 20841-L, spacer centre bolt between plates. The centre bolt goes thro the plates and engine casing itself, so not sure of where this spacer is needed. I would also like to ask the difference between STD 280, bolt uniting frame (350) and 011238 (500). And another, I cannot find a mention of a bolt uniting the frame at the top.
Regarding the spare frame, it appears identical to my 1947 G3l, without pulling every thing apart. The engine plates appear much different to the others I have but once again I am loath to pull much apart given that it is running beautifully at this moment.

Thank you
Ray.
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