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 SPRIDDLER » Mon Dec 16, 2019 9:43 pm

cfaber wrote:Okay, new drain plug seems to be helping, it's scavenging much better, .....

With that in mind, how different is the new sump plug compared with the original one? (Post a photo of both perhaps?)
I've absolutely no idea why the new one would improve the scavenging unless the original plug was obscuring the oil pick-up gallery in the c/case.
However, (and I'm reluctant to suggest this in public :oops: ), but since the new plug improved things why not experiment temporarily by fitting as many washers as possible on the new plug so that it will protrude even less into the c/case?
It'll only take ten minutes and you've nothing to lose by giving it a go.
(No, I haven't been at the Christmas sherry ;) ).
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Re: Wet sumping while running

Postby cfaber » Mon Dec 16, 2019 9:46 pm

SPRIDDLER wrote:
cfaber wrote:Okay, new drain plug seems to be helping, it's scavenging much better, .....

With that in mind, how different is the new sump plug compared with the original one? (Post a photo of both perhaps?)
I've absolutely no idea why the new one would improve the scavenging unless the original plug was obscuring the oil pick-up gallery in the c/case.
However, (and I'm reluctant to suggest this in public :oops: ), but since the new plug improved things why not experiment temporarily by fitting as many washers as possible on the new plug so that it will protrude even less into the c/case?
It'll only take ten minutes and you've nothing to lose by giving it a go.
(No, I haven't been at the Christmas sherry ;) ).


You've read my mind and in fact I've got a stack of copper washers on it now. I plan on testing it out shortly. I'm also wondering if its at all possible for the other side of pump to draw in more oil than can be expelled by the scavenge side?
Fix it until it's broken!

Otherwise how will
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Re: Wet sumping while running

Postby SPRIDDLER » Mon Dec 16, 2019 10:00 pm

Surely the stroke of the pump and its delivery/return volumes are governed mechanically? I did wonder if the gasket on the forward plate which has the outlet for the rocker box had been fitted incorrectly, blocking the feed hole to the rocker box pipe but even so the total volume of oil being supplied by the pump wouldn't increase.

Another thought is whether the blanking plugs at the guide pin end of the plunger were leaking air and reducing the 'suck' of the pump......... :?

It's late here so I'll ponder it (yet again) whilst dropping off.
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Re: Wet sumping while running

Postby matchless » Tue Dec 17, 2019 3:42 am

Hi, I had a similar problem and it was driving me crazy (the same as you).
From personal experience, unless you strip the engine and measure all the parts for wear, you are wasting your time. So......Bite the bullet and strip the engine.

When I stripped my engine I found the main bronze bush was worn and this caused extra downward pressure on the oil pump plunger which in turn wore the oil pump tunnel oval. This allowed the return oil to bleed back into the sump.

I ended up replacing the timing side half as it was easier and cheaper than trying to convince a machine shop to make up a 'one-off' mandrel to accurately set up, counterbore and sleeve my original cases.

I hope this helps
Regards...........David

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Re: Wet sumping while running

Postby ajscomboman » Tue Dec 17, 2019 11:00 am

I think I'm beginning to agree here, it maybe time to dig deeper. At first my thought was more than likely a blockage given the fact that the motor had been built, now I'm wondering about the timing side axle bush and exactly how much wear is present. Too much and this will let the cases fill even if the pump is in reasonable condition.

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Re: Wet sumping while running

Postby SPRIDDLER » Tue Dec 17, 2019 12:40 pm

I'm also inclined to suspect the timing side bush, perhaps mislead by Colin's very first post:
cfaber wrote:From what I could tell, the engine was seized, though once I got it apart it appeared that the only issue was glue/pitch/seal? that had worked it's way down from the mating surface between cylinder and crank case. This crap was all over the inside of the engine and when I finally got it all apart I couldn't find any mechanical damage, just a sticky big end and a set of RSL8's that need to be replaced.

Without splitting the c/case halves the bush wear can be checked by removing the cam gears and lifting the end of timing side axle. I think the designed clearance axle to bush is 1 thou and the top limit of acceptable wear between axle and bush is 4 thou.
There are some shots of the bush in Colin's YouTube video although the camera movement was a bit too quick to have a clear look. One thing I could see was the sticky tar on the inside of the bush and on the timing side axle bearing surface.
(As an aside I believe this was the 'wet sumping' problem with JohnnieB's single that terminated his Jampot rally this year).
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Re: Wet sumping while running

Postby ajscomboman » Tue Dec 17, 2019 2:39 pm

SPRIDDLER wrote:I'm also inclined to suspect the timing side bush, perhaps mislead by Colin's very first post:
cfaber wrote:From what I could tell, the engine was seized, though once I got it apart it appeared that the only issue was glue/pitch/seal? that had worked it's way down from the mating surface between cylinder and crank case. This crap was all over the inside of the engine and when I finally got it all apart I couldn't find any mechanical damage, just a sticky big end and a set of RSL8's that need to be replaced.

Without splitting the c/case halves the bush wear can be checked by removing the cam gears and lifting the end of timing side axle. I think the designed clearance axle to bush is 1 thou and the top limit of acceptable wear between axle and bush is 4 thou.
There are some shots of the bush in Colin's YouTube video although the camera movement was a bit too quick to have a clear look. One thing I could see was the sticky tar on the inside of the bush and on the timing side axle bearing surface.
(As an aside I believe this was the 'wet sumping' problem with JohnnieB's single that terminated his Jampot rally this year).



It certainly was Nev, and there was plenty of it sloshing about in the cases and in the rear of the van by the time I'd got him back to site.

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Re: Wet sumping while running

Postby cfaber » Tue Dec 17, 2019 3:49 pm

Hm.. Well if I can't sort this without ripping the engine back down that'll be my next thing to investigate. That said, I did check the timing side bush for slop and end float and it was (IIRC) only 1 thou difference from the crank. I'll first pull the pump again and see if I can measure for oval of the bore
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Re: Wet sumping while running

Postby Dixter » Tue Dec 17, 2019 4:59 pm

Hi Colin: At the risk of repeating my self, I'll repeat myself. "Your earlier measurements do not add up!"

The British Army Inspection Standards show the Pump Spindle (not shuttle) measure 0.7180" / 0.7175"

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

Your measurement was 0.714".

Alarm bells should have gone off.. 4 thou below the minimum acceptable value as stated above. This spindle is a hardened and ground English steel part. There is no possible way this part could have worn 4 thousandths of an inch.

Next value stated was Bore = 0.715". A quick review of the published standards would show there was no way possible for the bore to be 0.715, this would have been smaller than when the engine was manufactured, and a new pump spindle would not insert. Alarm bells again. I'm at a loss to understand how these errors were accepted, knowing the pump was suspect.

If one were to assume a "cheap Chinese micrometer" was off by 4 or 5 thou but the error was "consistent" (my term), then one is being foolish and consistent wrongs never add up to a right!

However, that's water under the bridge. Moving ahead; kindly recognize that we are looking for a defect in this pump and 1 or 2 thousandths of an inch error... anywhere in the bore determines success or failure, much greater care in measuring tools and technique are demanded.

It may be helpful to those who do not regularly use telescoping bore gages to review this video. https://www.youtube.com/watch?v=R6YLK0F3ytc

Additionally as reported by several people who have suffered poor pump performance; the wear on the engine cases was deep in the body. Like looking for a needle in a hay stack, it helps if you know where and how to look. This writer has repaired 3 engines in the past where excessive wear in the bore made the engine unserviceable. This is not a simple task, but it is has helped in knowing where to look and when to 'throw in the towel' and scrap the engine.

You need to carefully measure the bore forward of the inlet and outlet ports inside the bore. You will need to measure a dozen times, in all planes and varying depths. A worn oval will measure differently depending on the axis of the gauge. This is why a 3 point bore gage is always preferable. As mentioned before, be careful not to 'trap' the telescoping gage in a port.

A cheap USB endoscope will help looking for gouging. They are readily found on ebay or Amazon for about $20 USD. Usual disclaimer.

And to end on a lighter note, allow me two quotes by one of my personal heroes. Lord Kelvin 1824-1907. "If you can not measure it, you can not improve it."

"Large increases in cost with questionable increases in performance can be tolerated only in race horses and fancy women."

Colin, I wish you every success.

Ciao, DC

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Re: Wet sumping while running

Postby SPRIDDLER » Wed Dec 18, 2019 10:04 am

Dixter wrote:Your measurement was 0.714"...........Alarm bells should have gone off........... 4 thou below the minimum acceptable value .....
Next value stated was Bore = 0.715". A quick review of the published standards would show there was no way possible for the bore to be 0.715, this would have been smaller than when the engine was manufactured,..........

If one were to assume a "cheap Chinese micrometer" was off by 4 or 5 thou but the error was "consistent" (my term), then one is being foolish and consistent wrongs never add up to a right!

You're quite right Dick; Colin's measurements don't have any credible relationship to the published Army spec'n.
However, assuming (foolishly!) his measurements were both consistently off by 4 or 5 thou the difference does reveal an acceptable clearance of only 1 thou 'twixt shuttle and bore.

I'm not fortunate enough to be as well endowed as either of you in the tool department. I have always had to rely on relative rather than absolute measurements from a Chinese digital caliper or ancient feeler gauges which have usually been sufficient.
I guess that if it isn't a worn timing side bush and in view of the Army spec'n. the next step is as you said, to re-measure, preferably using an accurate 3-point gauge.

I do wonder if the problem will eventually be traced to a 'slap-head' obvious yet overlooked cause :roll:. Probably not.
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