Definitive 1950 G9 Bottom end...

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Definitive 1950 G9 Bottom end...

Postby matg80s » Thu Jan 31, 2019 4:31 am

Hi all, apologies if this info has been done to death, There was a surge of posts in the 2010 - 2012 period but has tailed off and supply chain has changed somewhat also. Ive waded thru all 27 pages and although very helpful I still have queries.

Perhaps a close to the front freshen up will be handy for other newbies...

I just completed a 52 G80s patina refurb and Im considering a basket case 1950 G9 motor build for a spare rolling chassis and B52 box I have , motor is missing a fair bit but I can source most locally, Im looking for some definitive info regards crank, mains etc. I have only pics at this time..

My 1951 Niell manual shows main bearings as: Hoffman RLS 12 1/2- 3" OD-1"3/4" ID- 11/16" WIDE ; SKF CRL 11 yet I see other vendors stating "fits all twins" where said bearing size differs by 1/16". Also is the bearing floating caged inner single lip outer?

The crank appears to be a post 51 with the smaller centre bearing not sure about the centre web plate size yet, and round flywheel outers, Im presuming its compatible with thrust washers fitted etc, not sure of oversize/undersize yet, the journals look quite clean..

Barrels are 6 fins and approx 66.76 so 500 on oversize so correct..

Pushrods are tad over 8" so should be fine

The heads seem to be 55 with the oil groove on the rocker arms so they should be a go..

I have a choice of about 10 sets of cams so using an old article from the archives Ill attempt to identify correct profiles, any ideas?

I let a few of these Matchy Twins pass me by over the years so Id like to save this ol girl from the inevitable wall mount display.. My ignorance can't be offended so any corrections and info as to compatibility issues or build tips will be appreciated.. regards Matt...
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Re: Definitive 1950 G9 Bottom end...

Postby robcurrie » Thu Jan 31, 2019 7:55 pm

Hi Matg80s, where in SA are you located? If you are in Gauteng, come to the Classic Motorcycle Club in Germiston on Sunday 3 February, there are some projects and parts coming up for tender soon. When we were sorting parts and bikes into makes, there was a lot of G9 bits in the AMC pile. Ask for me or Colin Blackburn. You can PM me for contact details.
Regards
Rob Currie

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Re: Definitive 1950 G9 Bottom end...

Postby matg80s » Thu Jan 31, 2019 11:00 pm

Hi Rob thnx for your reply Im actually in Sth Aus, be a nice trip tho...

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Re: Definitive 1950 G9 Bottom end...

Postby robcurrie » Fri Feb 01, 2019 4:25 am

You're welcome to contact me if you come to South Africa. I'm sure someone more familiar with the G9 will be along shortly. Be careful of the chap who is an expert on twins - he will try sell you stuff on this forum :rofl:.
I will have a look through my literature in the meantime.
Best of luck

Rob C

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Re: Definitive 1950 G9 Bottom end...

Postby matg80s » Fri Feb 01, 2019 4:41 am

Ok mate, cheerz for the friendly invite and heads up, Im in no real hurry jus fishin at this stage, Matt

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