1965 Matchless G12

Joined
Nov 10, 2012
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2,948
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Hi All.
I am looking for to buy a 1965 G12.
Bike have the cylinder and head removed because had a continuos pistons seizing.
If i buy it i want to restore completely the engine.
So i need the workshop manual and the spare parts list.
Do you know why this engine types had this problem?.
Please, let me know who sells the books tor where i can buy them or have from web.
Thank you.
Piero
 
Joined
Jan 19, 2012
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1,049
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Hi Piero,

Welcome to the club! I have a genuine 1964 G12CSR (US spec) also in need of restauration.
There are a couple of weakness associated with this engine (as it's got the improved crankshaft, so that doesn't count) - it's advisable to recondition the conrods, or switch to G45 type steel conrods (made by Carillo) as I do. Also, the push in exhaust pipe to head joint isn't always gas tight - this can be rectified by expanding the pipe though.

Reasons for seizure is probably lean fuel mixture or wrong timing. Overheating will kill any engine. These engines have very long sleeves into the crankcase which are cooled by oil mist only. However, I don't think that is a reason for seizures.
I am fitting trick alloy barrels which will improve cooling of the engine and enhance the visual appearance.

Workshop manual and spare parts list can be downloaded from the danish AJS/M Owner's Club site. Just search for "Christian's archive".

-Knut
 
Joined
Nov 10, 2012
Messages
2,948
Country flag
Hi Piero,

Welcome to the club! I have a genuine 1964 G12CSR (US spec) also in need of restauration.
There are a couple of weakness associated with this engine (as it's got the improved crankshaft, so that doesn't count) - it's advisable to recondition the conrods, or switch to G45 type steel conrods (made by Carillo) as I do. Also, the push in exhaust pipe to head joint isn't always gas tight - this can be rectified by expanding the pipe though.

Reasons for seizure is probably lean fuel mixture or wrong timing. Overheating will kill any engine. These engines have very long sleeves into the crankcase which are cooled by oil mist only. However, I don't think that is a reason for seizures.
I am fitting trick alloy barrels which will improve cooling of the engine and enhance the visual appearance.

Workshop manual and spare parts list can be downloaded from the danish AJS/M Owner's Club site. Just search for "Christian's archive".

-Knut
Hi Knut,
please, could you let me understand better "Also, the push in exhaust pipe to head joint isn't always gas tight - this can be rectified by expanding the pipe though.".
Thank you.
Piero
 
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