Heavyweight Single Engine Mount

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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George Kaplan
Posts: 160
Joined: Tue Apr 25, 2017 1:24 pm
Location: York

Heavyweight Single Engine Mount

Post by George Kaplan »

I have a 1958 frame that I am fitting an earlier engine into. So far I have been using a set of empty 1953 crank cases to align everything. So far so good.

Earlier today I decided to see how things are with a complete engine fitted but have found that the bottom front engine mount changed from 5/16" to 3/8" in 1954.

For some reason my 1953 empty cases had this front mount bored out to 3/8" but my complete engine seems to be an unmolested pre-1954 engine with a 5/16" hole. Obviously the frame mounts are 3/8"

I cant be the first to fit an earlier engine into a later frame so what do folks usually do? I have 2 choices:

1. Bore out the engine mount to 3/8" and use a 3/8" stud

2. Make two top hat bushes to reduce the frame mountings to 5/16"

Which of the above would you do or would you do something else? (getting a later engine is not an option)

John.

P.S. At least this narrows down the date of my engine with the unusual number.


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raffles
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Posts: 609
Joined: Mon Jan 01, 1990 12:00 am
Location: NORTHAMPTONSHIRE UK

Re: Heavyweight Single Engine Mount

Post by raffles »

John
I would suggest that you bore the cases to 3/8". There are two frame parts to be tied together at that point and
top hat bushes would be a problem.
Tony
George Kaplan
Posts: 160
Joined: Tue Apr 25, 2017 1:24 pm
Location: York

Re: Heavyweight Single Engine Mount

Post by George Kaplan »

raffles wrote:John
I would suggest that you bore the cases to 3/8". There are two frame parts to be tied together at that point and
top hat bushes would be a problem.
Tony
Thanks for the input Tony and I think you are right.

Now that I have thought about it a bit more, the difference between the two diameters being so small would mean that the bush would have 1/32" wall thickness which is way too thin.

John
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AJS 500
Posts: 38
Joined: Wed Aug 05, 2015 5:27 pm
Location: KENT UK

Re: Heavyweight Single Engine Mount

Post by AJS 500 »

I've also fitted an earlier engine to a '57 frame.
My solution was to machine top hat bushes to suit after opening the frame holes up a tad. Makes removing/ fitting the engine easier as they stop the frame separating.


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George Kaplan
Posts: 160
Joined: Tue Apr 25, 2017 1:24 pm
Location: York

Re: Heavyweight Single Engine Mount

Post by George Kaplan »

AJS 500 wrote:I've also fitted an earlier engine to a '57 frame.
My solution was to machine top hat bushes to suit after opening the frame holes up a tad. Makes removing/ fitting the engine easier as they stop the frame separating.
Thanks for the tip AJS 500, I have bored my cases now but its good to know that both of my initial thoughts are both valid solutions.

John
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