AJS & Matchless Owners Club

Hi all.

I recently acquired a nice 1956 model 30. All sorted but... On my ride back home from a Club night, funny graunch noise from the engine. Clutch in, I coasted to a halt and called international rescue (a new Zealander pal with a Vivaro van). Anyhoo, back with bike up on the operating table for a look. Gearbox and primary drive are ok. Timing chest looks fine although not much oil came out when i opened that up. The strange thing is, the engine will turn for nearly a full revolution but then something jams.

Two questions, have any of you bright people had similar experience or can suggest the likely problem,

I now think maybe a valve/valve gear problem and I am about to remove the heads. Can anyone confirm the size of the nuts? I will need to procure a socket with a suitable diameter to get to them.

What fun:-)

Hi

Can't help with the problem, but I believe the cylinder head nuts are 5/16in. I use a short double ended box spanner on mine, with a socket on the other end. Have you tried rotating the engine with the primary chain removed to confirm the problem is at the motor end? Anything unpleasant stuck to the sump plug magnet? Have you looked down the plug holes to check for a stuck valve?

Good luck.

Malc

Hi

Sounds like something wrong with the valve gear, you can get a fair idea by looking down the spark plug holes from where you can see the valves opening and closing as you rotate the engine.

For a socket set, I can highly recommend these:
Thin walled and good quality.

Regards Mick

That's wierd, I can't post a link

Thanks very much both. I didn't remove the primary chain but i did dismantle the clutch. Gears all seem to select when i turn the mainshaft. I will however take the assembly off and check as u suggest.

I can see the exhaust valves moving but can quite see inlet.

Sending off for those sockets.

Cheers

if you pop the rocker boxes off you can see if a valve is stuck.

You have already checked the primary chain for foreign objects so that should be okay.

Not trying to worry you unduly but check the height of both pistons through the spark plug holes if the cranks snapped you will probably pick up a discrepancy or there will be a lag in the rise and fall between sides

Duncan wrote: ↑Fri Jul 30, 2021 11:54 am if you pop the rocker boxes off you can see if a valve is stuck.

You have already checked the primary chain for foreign objects so that should be okay.

Not trying to worry you unduly but check the height of both pistons through the spark plug holes if the cranks snapped you will probably pick up a discrepancy or there will be a lag in the rise and fall between sides

thanks Duncan. Will do.

Hi
the socket you need to remove the heads is 1/4" whit worth the club can supply you with a 3/8" drive set
Tony

Thanks Tony

Thanks all. Sealey sockets in hand, heads n barrels off. Huge play on lh conrod. More surgery tomorrow lol. Another question, does the model 30 engine come out leaving gearbox in place?

Yes,Remove the engine plate studs and loosen the gearbox studs and it'll come out. Remove the mag and dynamo to lighten it.
Dave.