1952 G9 Connecting Rod Question

Information relating to the Matchless G9 or AJS Model 20 500cc twin
Brian011952
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Joined: Thu Apr 25, 2019 7:17 pm
Location: Ca USA

1952 G9 Connecting Rod Question

Post by Brian011952 »

I recently purchased a dirty nasty grime covered G9 out of a shed. It was in the condition you would expect a shed find to be in, and I've completely dismantled it and I am getting ready to begin putting it back in order. Well, yesterday I received a nice surprise when I opened up the engine. At some point, a LONG ways back, someone had completely gone through the engine. There were new valves, new bores, new pistons, and here is my question? Are the original connecting rods on G9's polished from the factory? My engine has a beautiful set of polished alloy connecting rods.

I have the original manual, and I've searched this site, but I can't seem to find any information stating these connecting rods were polished or alloy originally. I already feel like I won the lottery finding the new parts inside this engine, but I'd like to know if the connecting rods are something unusual or just the normal for these engines?
SPRIDDLER
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Re: 1952 G9 Connecting Rod Question

Post by SPRIDDLER »

My chum 'Resto Ray' recently finished a 1952 Ajay Model 20 (same as G9 except tank badge and a few minor trimmings). The first part of the strip and resto was featured in the Jampot mag (end 2018 I think), and the editor has the final part, not yet published.
As bought:
2017-11-14 Rays 1952 model 20 001 (640x480).jpg
Finished. Everything done by Ray, including the hand painting:
Finished (640x480).jpg
I have photos of virtually all engine parts as stripped and before any work was done. If it's of any help here are the (untouched by Ray) conrods:
2018-04-09 020.JPG
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les ward
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Re: 1952 G9 Connecting Rod Question

Post by les ward »

All the twin conrods I have seen look like the ones in Spriddler's photos and I have a drawer full of them, but many not in such good condition.

Regarding the Resto Ray article, it was originally penciled in for the Sept Jampot but we ran out of space and the Oct Jampot (with the printers now) was taken up with the Jampot Rally. It is scheduled for the Nov Jampot.
SPRIDDLER
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Re: 1952 G9 Connecting Rod Question

Post by SPRIDDLER »

les ward wrote:All the twin conrods I have seen look like the ones in Spriddler's photos and I have a drawer full of them, but many not in such good condition.

Regarding the Resto Ray article, it was originally penciled in for the Sept Jampot but we ran out of space and the Oct Jampot (with the printers now) was taken up with the Jampot Rally. It is scheduled for the Nov Jampot.
Thanks Les. I thought I'd tip Brian off that there are articles which he may find interesting and maybe encouragement.
'There is a tide in the affairs of men
Which taken at the flood............'
Brian011952
Posts: 6
Joined: Thu Apr 25, 2019 7:17 pm
Location: Ca USA

Re: 1952 G9 Connecting Rod Question

Post by Brian011952 »

SPRIDDLER wrote:My chum 'Resto Ray' recently finished a 1952 Ajay Model 20 (same as G9 except tank badge and a few minor trimmings). The first part of the strip and resto was featured in the Jampot mag (end 2018 I think), and the editor has the final part, not yet published.
As bought:
2017-11-14 Rays 1952 model 20 001 (640x480).jpg
Finished. Everything done by Ray, including the hand painting:
Finished (640x480).jpg
I have photos of virtually all engine parts as stripped and before any work was done. If it's of any help here are the (untouched by Ray) conrods:
2018-04-09 020.JPG

Thank You, that answers my question. Looks great, and that's what my rods look like too.
Brian011952
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Joined: Thu Apr 25, 2019 7:17 pm
Location: Ca USA

Re: 1952 G9 Connecting Rod Question

Post by Brian011952 »

Thanks for the quick responses. My question has been answered as to the polished connecting rods.
matchless
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Joined: Fri Jan 01, 1999 12:00 am
Location: NSW AUSTRALIA

Re: 1952 G9 Connecting Rod Question

Post by matchless »

Hi, Just some additional info on the twin con rods (Yes they were polished and weight matched). When rebuilding an engine it is imperative to match the conrods with the correct crank.
Early rods (1949 - 1951) had a small cross section rod and were very light. These must be matched to the early (Light) cranks with the large centre main bearing.
Later model cranks had three different weights (Different balance factors ) and must be matched with a choice from three different (weight) types of conrods.
It should be noted that as the factory increased the capacity from 500 to 550 to 600cc, the cranks were increasingly made heavier, consequently, you will find the con rods were made heavier to equalise the balance factors.
Even though all the twin conrods have the same part number, Do not mix any of the earlier rods with later rods, otherwise, the engine will be out of balance.

Regards............David
Mick D
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Re: 1952 G9 Connecting Rod Question

Post by Mick D »

matchless wrote:Even though all the twin conrods have the same part number, Do not mix any of the earlier rods with later rods, otherwise, the engine will be out of balance.
Hi

That's interesting - is there a method for owners to determine what crank they have and what weight rods suit it? What was the weight range of rods used?

Regards Mick
matchless
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Re: 1952 G9 Connecting Rod Question

Post by matchless »

Look at model 20B crankshaft post in the Forum.
Mick D
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Re: 1952 G9 Connecting Rod Question

Post by Mick D »

Hi

Thanks for the pointer, but no information on how to match the con rods to the crank, anyone know how this is done?

Regards Mick
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