Wet sumping

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Location: Aberdeenshire

Wet sumping

Postby Oggers » Wed Apr 17, 2019 11:05 am

Right...pursuant to earlier posts, I drained the sump 6 days ago and replaced the plug. Bike on centre stand. Drained again last night and about half a pint issued forth. Therefore, it seems I am getting static wet sumping, which if left longer, I guess would permeate through the crankcase bearings, into the chaincase, overflow through somewhere - looked like the inspection cover last time - and spray everthing to the rear with oil.

So - what to do in the meanwhile

Dove tap/microswitch - pricey, but seems to work.
Plain tap - too risky. I fear I would forget that one time, and that is all it takes.
Thicker oil as Mick suggested - worth a try...on 20/50 at present
Drill and tap sump plug for a wing bolt/O ring - making draining easier before any ride out.

Manual also suggests checking feed pump fixing screws on the pump plate - one for later.

Thoughts?

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Re: Wet sumping

Postby Mick D » Wed Apr 17, 2019 12:51 pm

Hi Oggers

Well that's fairly conclusively diagnosed the issue.

I'd go for SAE 50 mono grade oil, now we are into summer up here ;) normal use should keep the sump level within limits.

For a permanent fix I'd investigate reconditioning the delivery pump - modifying the sump plug is OK, (rather have to replace a drain plug than sort out stripped threads in the crank case), but also adds another component to fail unless you fit a locking device to the drain plug.

Regards Mick

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Posts: 87
Joined: Mon Jan 14, 2019 5:37 pm
Location: Aberdeenshire

Re: Wet sumping

Postby Oggers » Wed Apr 17, 2019 2:07 pm

Hi Mick

Inclined to agree with Mono SAE 50. Easiest possible part remedy for sure. Any particular brand? I admire your faith in the Scottish summer, but if it was anything like last year.......

The drain within a drain - as it were - is a common fix on classic cars where access is a bit of a pig, and a strippped thread on the weak casting would present a major problem. Should be OK with a 6mm wing bolt. Plug hex seems pretty thick....

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