Manifold repair and parts

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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BruceB
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Manifold repair and parts

Post by BruceB »

I had a bolt in my manifold strip today on a run, its completely lacking in thread so will have to be helicoiled or replaced. The question I have is that the spares book contradicts what I have fitted at the moment and I am not sure what is in the spares book will actually fit.
The book seems to imply that there is a thick black insulating spacer between the carb and the manifold, plus there are studs in the manifold rather than bolts.
Mine had bolts and no thick spacer and its a bit tight if I have a spacer and or fit studs to get the carb on.
Which version is correct? and does anybody know of a spare manifold lying around for sale?
66 BSA Spitfire MK11
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clive
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Re: Manifold repair and parts

Post by clive »

Bruce please use either the website adverts (which then go in the magazine) or the wanted section of the forum to try to find the manifold. Regards Adverts Editor.
clive
if it ain't broke don't fix
g5wqian
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Location: near swindon wilts

Re: Manifold repair and parts

Post by g5wqian »

not sure if this is of any use to you Bruce , probably find one cheaper through the club though .



https://www.ebay.co.uk/itm/AJS-MATCHLES ... rk:11:pf:0
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dave16mct
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Re: Manifold repair and parts

Post by dave16mct »

No that's for an earlier 500cc with pre-monobloc carb.
It should have the spacer and use studs. I know it's hard to remove so some use bolts to make it easier. Shouldn't be problem as you don't take the carb of too often.
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Mick D
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Re: Manifold repair and parts

Post by Mick D »

Hi

I read the 60 parts list as the carb being secured to the manifold by two bolts part number 026749 and having an insulator part number 024308 - any chance that you have this later manifold, (part number 026048).

As far as a repair, I'd helicoil it.

Regards Mick
MalcW
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Re: Manifold repair and parts

Post by MalcW »

My '60 bike has studs, and has the thick insulating washer.

Malc
BruceB
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Re: Manifold repair and parts

Post by BruceB »

I ordered a 5/16 helicoil kit last night and am going to just insert a couple of helicoils into the original manifold, it seems cheaper and easier to do this than buy another manifold that may have the same problem, and it will be stronger than the original.
My manifold had just a thickish gasket between the carb and manifold. Looking at the parts book it definitely says thick spacer and studs, from an engineering point of view a stud and nut would have been a better system rather than a bolt screwed into soft alloy so seems to make sense to me.
There isn't much room here so was just looking for any experience on what folk had fitted and whether it gave them any issues, studs do look like they may be an issue and certainly with a thick spacer my trumpet is going to be in the hole in the cover it faces rather than a few mils short of it.
The manifold I have has a different number on it but I have been led to believe it is correct, despite being different to the actual part number, I think it is something like 025091.
66 BSA Spitfire MK11
77 Yamaha XS750 Triple
98 Suzuki Bandit GSF600S
78 Honda Superdream (rebuilding)
51 Cyclemaster (in queue)
56 G11 bitsa (in boxes awaiting courage)
78 Series Landrover (rebuilding)
72 MG Midget (in queue)
06 Honda XL1000
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ajscomboman
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Re: Manifold repair and parts

Post by ajscomboman »

The carb spacer on a 650 twin will be only 1/8th thick there's not enough room for anything thicker and for 59 it's two studs to hold the carb on the manifold. For the later 60 onwards twins with the larger manifold it went to 2 bolts to make removal and fitting easier.
BruceB
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Re: Manifold repair and parts

Post by BruceB »

As usual, this issue has opened up others. I tried to identify the carb, thinking about carrying out a quick rebuild while I had it off. The only identification I can find is the marking M37 which I am assuming means that it is a 389/31 amal. Since my checking of the Burlen Fuels site seems to indicate that the carb should be a 389/29 i am now assuming I have the wrong carb.
Can anyone confirm that I have the right meaning from the M37 marking and whether it is simply jet sizes that are going to different?
The 389/29 does not seem to be available and the easiest course would be to simply buy a service kit and the correct jets and not worry about the flange markings, this may alreay be in place if someone has replaced the carb (it doesn't look 59 years old) and change the jets because of the same availability issue.
66 BSA Spitfire MK11
77 Yamaha XS750 Triple
98 Suzuki Bandit GSF600S
78 Honda Superdream (rebuilding)
51 Cyclemaster (in queue)
56 G11 bitsa (in boxes awaiting courage)
78 Series Landrover (rebuilding)
72 MG Midget (in queue)
06 Honda XL1000
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ajscomboman
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Re: Manifold repair and parts

Post by ajscomboman »

The 389/29 is a code relating to the factory jetting, 29 being the important number. Basically the carb could be any 1" 1/8th bore 389 monobloc, the jetting as the works manual should be 400 main jet, No.3 slide, 106 needle jet and the clip in the centre notch of the needle. Easy way to check the size is to measure the diameter of the opening on the mounting flange.
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