AJS & Matchless Owners Club

Hello.

Helping a friend rebuild his 1959 650 twin, it has a Siamese exhaust on it but he wants to fit a duel exhaust, but we are unsure what heads it has as there seem to be a few different types.

Our engine has embossed

Head: 026053

barrel: 025040

and the stamping on the case is 59/31x0762

if someone could give us the part numbers for the right pipes would be highly appreciated.

The engine has mixed parts. The barrels have a 1959 part no. with 3in top spigot & the heads 1960-up with 3-1/16in. recess for the spigot. I don't know what pistons but 1959 pistons are compatible only with 1959 heads. Before trying to solve the pipe issue, change the top end so that Cylinders, heads & pistons are all 1959 or all 1960-up. Regards, Don.

Hi there, i am also having header pipe issues. My bike is a Mod 31 1959 with original heads & barrels. The 59 heads are different to the 1960 onwards/CSR.

The usual manufacturers of the header pipes in the UK have run out and can't tell me when they will manufacture any.

I enquired if i could use the 1960 pipes they said that the angle of the exhaust port is different on the 59 model.

So i would say that if your bike has the later heads ( these have cross finning on the bottom fin) then you could fit the G12/Model 31 pipes ffom 1960 onwards.

Alternatively decide which silencers you like best - Matchless or Ajs ( different) and get some headers made up to suit. ( there seems to be lots of fabricators in the US).

Hope this makes sense.

Steve

Hello, thank you for your help, I will check the spigot tommrow morning, the bike did have a blowing head gasket


Yes heads have the cross fins under the exhaust ports.


Funny enough my job once was sand bending exhausts for Nortons,

The heads are loose on the barrel spigots and the spigot holds the gasket faces apart by about 30 thou but the head gasket is nearly 2mm thick. I gess it has the 1960 pistons in it as they seem to match the combustion chambers