Wet sumping while running

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Re: Wet sumping while running

Postby Dave T » Sun Dec 08, 2019 10:46 am

Hi Mr Faber, looking at your earlier post with pictures of your wonderful pipework (really neat!) I noticed, but did not comment on, the nut holding your oil pump pin does not look standard! I had issues with mine when I bought my present G80 as someone had fitted a very thick copper sealing washer under it (none is necessary or shown in the manual) which led to damage to pin and plunger as the pin barely entered the plunger groove.Perhaps if yours is non standard it could be causing your problem?
Really nice restauration! I hope it's not being spoilt for want of such a small thing!
Dave.
PS it was Mick D's last post that made me think of this, I don't have many original thoughts :D

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Re: Wet sumping while running

Postby SPRIDDLER » Sun Dec 08, 2019 12:14 pm

Dave T wrote:Really nice restauration!


I see what you did there Dave ;) A feast for the eyes. Only in France, eh?
Bon appétit ! :beer:

(Apologies for being Off Topic).
I poke badgers with spoons.

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Re: Wet sumping while running

Postby cfaber » Sun Dec 08, 2019 5:13 pm

Thanks for the quality responses folks! Here's what I've checked so far and the state of various items:

  • The scavenge pick up at the bottom of the sump was checked before reassembling the case and it was clear (air gun check)
  • The shuttle actuated correctly on the pin after assembly
  • As far as I could tell, all oil galleries were clear (checked with air) after assembly
  • After assembly the engine was allowed to sit with oil in it to allow oil everywhere before starting

Now it's been started a few times and the results are
  • Oil pumps throughout the engine and lubricates everything, from what I can see
  • Some oil is returned to the tank, however after about 10 minutes of run time I've lost half the oil to the case
  • The guide pin was removed and reinstalled to verify correct pin orientation
  • The guide pin bolt was replaced with a brand new one as the old one had a dodgy head (but length / fit was perfect)
  • The scavenge side plate was removed to verify pin placement and shuttle actuation
  • The piston moved about 1/4" in and out though the 8 revolutions of the engine and was not sloppy (as observed with the plate removed)
  • Prior to removal of the end plate no oil leaking was observed
  • The return pipe was removed to verify that it was clear without obstruction and oil drained out of it freely (all over my floor)
  • Visual inspection of the return pipe drilling appears clear (but I didn't pull the shuttle out and verify with air)
  • I tried running without the filter to see if that had any affect - none was observed
  • The crank drain plug appears to be original, with rubber gasket fitted. It does not appear to have a magnet insert on it (so maybe not original?)
  • The crank drain plug does not appear to bottom out


I haven't run a drill bit up the scavenge pick up drilling or pulled the drilling plugs from the pump, I also haven't removed the pump itself after reassembly.

And just to make sure, there is no way to install the shuttle backwards right? I seem to recall this being the case, but this was reassembled a year ago +.
Fix it until it's broken!

Otherwise how will
anything get done?

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Re: Wet sumping while running

Postby Mick D » Sun Dec 08, 2019 5:46 pm

Hi

Why not remove the return line at the engine and sleeve on a bit of pipe, start the engine and observe the flow. Stop the engine, transfer the returned oil to the tank and see if it's still wet sumping - will isolate the issue to the tank or engine, (could be a partial blockage in the oil tank return internal line).

Regards Mick

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Re: Wet sumping while running

Postby Duncan » Sun Dec 08, 2019 6:11 pm

cfaber wrote:
[*] The crank drain plug appears to be original, with rubber gasket fitted. It does not appear to have a magnet insert on it (so maybe not original?)


Magnet sump plugs were introduced in the 1956 model year for the singles, so likely to be original.

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Re: Wet sumping while running

Postby cfaber » Sun Dec 08, 2019 6:14 pm

Is there a check valve anywhere on the scavenge side that I've completely missed?
Fix it until it's broken!

Otherwise how will
anything get done?

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Re: Wet sumping while running

Postby Dixter » Mon Dec 09, 2019 6:26 pm

Hi Colin: I feel you buddy, you have spent a lot of time and have demonstrated neat and straight forward work. Here are a few observations.

In your earlier list of things done, you make reference to a rubber washer under the head of the crankcase drain plug. This really must be either fiber or a metal crush washer in copper or aluminum. The plug must be secure. Vibration, and you will have plenty, could cause the plug to fall out with life threatening consequences.

If you did not have a chance earlier, download this British Army reference manual on maintaining these bikes and go to Section 4: Oil pumps. Here's the link.

http://archives.jampot.dk/book/Workshop ... ndards.pdf

Section 4 contains the physical measurements for the oil pump spindle and pump bore, scavenge and supply. Note columns 2 & 3. Pull the rear cover plate from the engine, strip out the spindle, and measure and inspect everything.

Please note: Attempting to get a clear measurement with ether a dial/vernier/digital caliper will result in a false reading. As will inserting the new pump spindle, 'big end first' to gauge the fit. The pump bore is worn "barrel shape'. There is zero wear directly under the cover plate and measuring this aperture will not help. You will need a telescoping bore gage or ideally 3 point bore gage. Caution Here! There are multiple ports inside the pump bore which can "trap" a telescoping bore gage. Assuming the bore has 'acceptable' dimensions, inspect with strong light and perhaps a borescope. Look carefully for scoring inside the pump bore, where the scavenge port on the inlet side, meets the port in the pump spindle. The usual failure mode here is; swarf sucked into the pump bore is partially trapped by the pump spindle and a trench is plowed in the pump bore as the spindle rotates.

We all know that most all pumps are far better at pushing than pulling. The smart farmer always had a pail of water handy to "prime the pump"

And to your last question, No, there are no check valves. AMC relied on an oil film in the pump bore to support a partial vacuum, lifting the oil, half a foot, where it could be pumped up to the oil tank. In the off cycle, oil would slowly seep back down the return pipe replenishing the oil film in the pump.

Section 4.jpg


Telescopic.jpg
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Dick Casey
The RideNut

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Re: Wet sumping while running

Postby willowbedone » Mon Dec 09, 2019 7:02 pm

hi Colin I really feel for you I may be right of course but is the oil pump plunger correct and the timing side axle correct to match the plunger
Just a thought
Ian

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Re: Wet sumping while running

Postby cfaber » Tue Dec 10, 2019 4:24 pm

Hi guys,

Thanks for the replies. I've tested output from the return, right off the engine and it's still anemic. The next thing I'll try is to pull the pump, check the bore size in relation to the shuttle, and while I've got it apart I'll try and run a drill up the drilling from the bottom and one through the side to see if there's anything in there keeping it from pumping.
Fix it until it's broken!

Otherwise how will
anything get done?

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Re: Wet sumping while running

Postby cfaber » Wed Dec 11, 2019 5:33 pm

Does this drilling intersect the drilling for the sump?
Image

And if it does, do you need to pull the pump to access it fully or can I check that it's clear with the pump in place?
Fix it until it's broken!

Otherwise how will
anything get done?

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