classic motorcycle forum

Motorcycle Discussions => British Bikes => Topic started by: dynamic on July 17, 2025, 05:31:22 PM

Title: AJS 16M 1951
Post by: dynamic on July 17, 2025, 05:31:22 PM

I have an oil leak from the lower oil pump / timing case (lower slot screw ) I need to replace the gasket

 also is this chain in need of replacement ?

I notice there are no timing marks on crank / magneto do I just centre punch each sprocket and mark chain cover casing

all input gratefully recieved

Title: Re: AJS 16M 1951
Post by: dynamic on July 17, 2025, 05:32:08 PM

pic 2

Title: Re: AJS 16M 1951
Post by: Rex on July 17, 2025, 05:58:23 PM

No, you can't just centre pop the gears as you need to synchronise the position of the piston on the firing stroke with the position of the mag points.
Simple enough if you have a manual. FW Neill is a good one.

Title: Re: AJS 16M 1951
Post by: R on July 17, 2025, 11:12:30 PM

Since the sprockets look to be in excellent condition, the chain may not be worn ?
Can you just pack the magneto up a bit higher on its platform ?
Or is the platform adjustable even, with slotted holes on one side ??

Title: Re: AJS 16M 1951
Post by: john.k on July 18, 2025, 01:39:56 AM

Loose enough to wear away the case ............I d replace the chain.......you could pack up the mag ,its base mounted

Title: Re: AJS 16M 1951
Post by: dynamic on July 18, 2025, 08:14:54 AM

thanks all for posting I will post my progress soon.

Title: Re: AJS 16M 1951
Post by: esoracer on July 18, 2025, 08:19:49 PM

I have one of these models. The magneto chain is adjustable by moving the magneto platform which is designed for that purpose. The sprockets are not keyed, they just have a tapered fit and if you use a puller to get them off the taper you will have to re time the ignition.

Title: Re: AJS 16M 1951
Post by: esoracer on July 18, 2025, 09:01:22 PM

Also, as you have to remove the sprockets in order remove the timing case  to change the gasket I would try just removing the bottom screw, cleaning it and coating it with silicone jointing compound and replacing it and see if that slows the leak.

Title: Re: AJS 16M 1951
Post by: dynamic on July 19, 2025, 08:49:37 AM

thanks for the info esoracer bike is losing approx. 300ml each time engine is run, I will keep all posted on progress