AJS & Matchless Owners Club

Good Afternoon,

Bought a 1949 16M …my first AJS …exported to Denmark and registered there in early 1950, same owner until sold and imported back to UK in 2018 and been sitting a while …just working my way through the faults to get it running reliably …so two questions firstly spitting back through Carb after flooding issue sorted, suspect an air leak i found the exhaust header could be pulled out head very loose so i suspect that may be the issue what is the best product to seal this, exhaust sealant or silicon ? i have stripped carb and will clean it out and use new gaskets on inlet manifold, valves seem good, push rods spin nicely and looks like it has been well maintained…so second question is it really worth lifting the head as i dont want to unnecessarily disturb things if its running at the moment. Obvs if i cant resolve to spitting back ill lift the head and look at valves…

most use silicon bathroom sealant (clear) to cure a leak at joint , id not use exh paste as its so difficult to remove when you want to get exh off

Cheers yeah i just remembered my A10 was same carb to manifold nuts were very tight and gaskets look suspect very dirty cheers

g80csp11 wrote: ↑Mon Oct 16, 2023 3:05 pm most use silicon bathroom sealant (clear) to cure a leak at joint , id not use exh paste as its so difficult to remove when you want to get exh off

I tried that... useless. It won't stand the high pressure, very high temperature, exhaust gas at the cylinder head joint. It blew out the first time I started the engine. If you do use silicone sealant, use the red high temperature stuff, but that is only a short term fix. I found the only sealant that worked for any length of time was the stuff that is sold for sealing flue joints on wood burner stoves.

Think I've seen somewhere you use a taper to slightly flare the end of the header pipe to get a tighter fit

Steve wrote: ↑Sun Oct 22, 2023 9:53 pm Think I've seen somewhere you use a taper to slightly flare the end of the header pipe to get a tighter fit

There is this picture in the club archive: https://www.jampot.com/archives//AJS%20 ... 20Port.gif its probably in one of the manuals.

its possible to get a set of exhaust/tail pipe expanders from auction sites.

On the cheap clear silicone front, I have been using it for years on all exhaust joints to seal and prevent air being sucked in, it has never burnt and can be rubbed off without undue effort when remaking the joint, I always let it set overnight before firing up the engine.

Duncan wrote: ↑Sun Oct 22, 2023 10:55 pm

Steve wrote: ↑Sun Oct 22, 2023 9:53 pm Think I've seen somewhere you use a taper to slightly flare the end of the header pipe to get a tighter fit

There is this picture in the club archive: https://www.jampot.com/archives//AJS%20 ... 20Port.gif its probably in one of the manuals.

its possible to get a set of exhaust/tail pipe expanders from auction sites.

On the cheap clear silicone front, I have been using it for years on all exhaust joints to seal and prevent air being sucked in, it has never burnt and can be rubbed off without undue effort when remaking the joint, I always let it set overnight before firing up the engine.

Ah that's probably where I saw it, good to know I wasn't having another senior moment

If you do use the metal tapered plug to widen out the pipe be very careful not to over-do it. I've had success with this and I've also used silicone with no problem.
Dave.