Model 30 crank centre bearing. Woe is me :-)

Information relating to the Matchless G11 or AJS Model 30 600cc twin
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Victor Johnstone
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Model 30 crank centre bearing. Woe is me :-)

Post by Victor Johnstone »

Ok got a very competent engineer. Automotive Resources. Dundee. He reckons the centre main is bad and notwithstanding weakness would need to go to -060. Currently -40. Question; are -060 available? Any thoughts you kind knowledgeable people? Maybe and sadly the crank is now a dinghy anchor. :-)
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les ward
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Re: Model 30 crank centre bearing. Woe is me :-)

Post by les ward »

The club have centre main shells at 60 thou oversize.
Victor Johnstone
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Re: Model 30 crank centre bearing. Woe is me :-)

Post by Victor Johnstone »

Good news Les. Thanks. I will contact them today.
SPRIDDLER
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Re: Model 30 crank centre bearing. Woe is me :-)

Post by SPRIDDLER »

Victor Johnstone wrote: Thu Aug 26, 2021 7:27 pm Ok got a very competent engineer. Automotive Resources. Dundee. He reckons the centre main is bad and notwithstanding weakness would need to go to -060. Currently -40.

I know little about twins but if you're not aware of it there are radii which must be maintained when grinding............
See here:

http://archives.jampot.dk/technical/Spe ... _twins.pdf
Last edited by SPRIDDLER on Fri Aug 27, 2021 9:27 am, edited 1 time in total.
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Victor Johnstone
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Re: Model 30 crank centre bearing. Woe is me :-)

Post by Victor Johnstone »

My bike is 1956. I am not at home just now so cannot check. I see the spares sect refer to the shells fitting post engine number 7000. Could you point me at a year/number system?
Victor Johnstone
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Re: Model 30 crank centre bearing. Woe is me :-)

Post by Victor Johnstone »

Thanks Spriddler. Yes and thanks again. Crucial.
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Duncan
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Re: Model 30 crank centre bearing. Woe is me :-)

Post by Duncan »

Victor Johnstone wrote: Fri Aug 27, 2021 9:27 am My bike is 1956. I am not at home just now so cannot check. I see the spares sect refer to the shells fitting post engine number 7000. Could you point me at a year/number system?
Hi I believe this refers to the very early 500's (late 1940's very very early 1950's) that had a different centre bearing/thrust washer design.
Groily
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Re: Model 30 crank centre bearing. Woe is me :-)

Post by Groily »

I think if the crank cleans up with good radii on the centre main at 60 under, you'll be OK. Back in the day, there were those who took the crankpins to 80 under and used the shells from Minis, from memory having to change the side the locating tangs of the shells were on. When I bought my 500 back in '76, it was at -80, done that way but I can't remember what the centre main was on. It had done a lot of miles with its PO and with me before I opened it up for a general rebuild after one of the wire-wound pistons 'came apart in me 'and guv'nor'. I've read that the Mini route was never a good idea for reasons I've now forgotten . . . but it worked for whoever did mine.

T&L say they have sprayed journals on these back to size when they've had to, successfully. Again, I assume it needs good radii under the new metal to guarantee integrity, but the guys in Dundee could probably do the same if it came to it. So hopefully not a dinghy anchor.

I'm not up on this - someone here will know though - but I think the earliest engines had narrower journals maybe, hence the caveat on the parts. There was something different about those cranks I'm sure, but I've never had one to compare.
One very minor thing with the shells might be the need to check the chamfer on them, to make sure they clear the radii. I THINK the club stock will all be spot-on, but I had to make a jig and take a bit off some sets from I can't remember who a few years back to prevent the outer edges of the shells binding on the shoulders next to the webs.

(Duncan just explained, there we go!)
Victor Johnstone
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Re: Model 30 crank centre bearing. Woe is me :-)

Post by Victor Johnstone »

Thanks very much all. This is a great club!
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