AJS & Matchless Owners Club

Lads are L/W'S G 5 prone to wet sump ,after short periods of idleness my g5 emits clouds of oil smoke and after awhile clears.when inspecting the spark plug it's generally black and oily. I would appreciate any advice you experts put my way cheers Paul

Wet sumping is a problem on heavyweight singles usually only if the pump is very worn or the housing damaged. It is not usually a problem. The oil pump in the lightweight is I think the same design and so should not wet sump unless damaged or worn. I am afraid the symptoms you describe do sound like wet sumping. You will either need to investigate or carry on regardless! Best bet is to use it more often.

My 1960 G5 I bought as non runner and have been putting it right for 2yrs, logistics and spares slowed everything. If you look back no further than Apr 19 under Vigo you will see similar symptoms. The wrong carb was fitted (blue smoke oil accepted). That corrected the bike starts and runs great for 6 or 7 mins then oil puts the fire out, swimming (search pic). At the moment it's head and barrel off to fault find. Barrel porosity from head oil feed? Valve guide wear, too much oil in my case. Oil up from crank case?
My head gasket is covered in oil and the copper part of the gasket (composite) is being pushed egg shaped. My next step will be to lap the head to barrel for true and use a full copper head gasket.

Good luck

vigo wrote: ↑Tue May 04, 2021 10:53 am My 1960 G5 I bought as non runner and have been putting it right for 2yrs, logistics and spares slowed everything. If you look back no further than Apr 19 under Vigo you will see similar symptoms. The wrong carb was fitted (blue smoke oil accepted). That corrected the bike starts and runs great for 6 or 7 mins then oil puts the fire out, swimming (search pic). At the moment it's head and barrel off to fault find. Barrel porosity from head oil feed?
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quiz picture a few years back showed a fix for the barrel porosity. I assume the hole is bored out before the tubing is fitted but it might not be necessary.

I remember having a similar problem about 40 years ago with a 250CSR, a skim of the head and barrel fixed it. The heads do warp sometimes, especially near the exhaust port. I was blowing gaskets about once a week, both copper and composite, oil everywhere.