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 cfaber » Sat Dec 14, 2019 5:32 pm

Okay, new drain plug seems to be helping, it's scavenging much better, however the crank is still filling up with oil faster than it can scavenge out. Everything is clear, the bore diameter vs the scavenge pump diameter is 1 thou difference. Other suggestions?
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Re: Wet sumping while running

Postby SPRIDDLER » Sat Dec 14, 2019 7:28 pm

This thread is a head scratcher and you seem to have covered all the possibilities without any real conclusion.
1 thou clearance plunger to body is within the Army maintenance and inspection spec'n.
e.g.
Bore: High 0.7195" Low 0.7183".
Plunger: High 0.7180" Low 0.7175"

A wild guess and clutching at straws but I wonder if the oil tank or return spigot/filter housing has a blockage. Perhaps disconnect the return pipe at the tank spigot and add a bit of pipe so that you can re-route it to return the oil directly into the tank oil filler hole at the top rather than via the bottom spigot and the filter.

Just to recap: You say the c/case is still filling faster than emptying. I'm a bit surprised that after changing the sump plug the return flow is only 'much better' rather than satisfactory. It may be good enough and maybe it's a silly question but how are you judging that? What are the symptoms - smoky zorst? chaincase filling up? Oil tank level dropping continuously? I'm rambling a bit and stating the obvious I know but the oil level will drop on start-up after the c/case has been drained but after the oil begins returning to the tank it should stabilise at a constant lower level.

Clive mentioned to check that the plunger guide pin matched the annular groove in the plunger. It should be 1/4" diameter and seems correct from your photos in the other thread. Earlier ones were 3/16" but if it has the smaller guide pin the pump won't be very efficient but I would think that even so the return should still exceed the flow rate.
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Re: Wet sumping while running

Postby cfaber » Sat Dec 14, 2019 8:19 pm

SPRIDDLER wrote:This thread is a head scratcher and you seem to have covered all the possibilities without any real conclusion.
1 thou clearance plunger to body is within the Army maintenance and inspection spec'n.
e.g.
Bore: High 0.7195" Low 0.7183".
Plunger: High 0.7180" Low 0.7175"

A wild guess and clutching at straws but I wonder if the oil tank or return spigot/filter housing has a blockage. Perhaps disconnect the return pipe at the tank spigot and add a bit of pipe so that you can re-route it to return the oil directly into the tank oil filler hole at the top rather than via the bottom spigot and the filter.


Yeah I checked this, it's totally clear and air / oil passes freely though it

SPRIDDLER wrote:Just to recap: You say the c/case is still filling faster than emptying. I'm a bit surprised that after changing the sump plug the return flow is only 'much better' rather than satisfactory. It may be good enough and maybe it's a silly question but how are you judging that?


Just peaking at the stream of oil returning into the tank, it's steady but not great. I'd say the stream necks down to about half it's size right out of the spigot. (not scientific measurement by any means)


SPRIDDLER wrote: What are the symptoms - smoky zorst? chaincase filling up? Oil tank level dropping continuously? I'm rambling a bit and stating the obvious I know but the oil level will drop on start-up after the c/case has been drained but after the oil begins returning to the tank it should stabilise at a constant lower level.


Yeah,
  • smoky exhaust
  • oil level dropping in the tank
  • oil belching out of the breather
  • burned oil in the exhaust


SPRIDDLER wrote:Clive mentioned to check that the plunger guide pin matched the annular groove in the plunger. It should be 1/4" diameter and seems correct from your photos in the other thread. Earlier ones were 3/16" but if it has the smaller guide pin the pump won't be very efficient but I would think that even so the return should still exceed the flow rate.


I measured the guide pin vs the scroll in the shuttle and it's anywhere form 1 to 3 thou clearance all the way around. There is a small perceptible movement on the shuttle if you push it back and forth after seating the guide pin, but it's extremely small, the carrier bolt is new from the spares shop and length of thread / fitment of pin is identical to the one I replaced it with.
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Re: Wet sumping while running

Postby SPRIDDLER » Sat Dec 14, 2019 9:07 pm

Thanks for clarifying, Colin.
Casual straw-clutching........
In one of your pics in the other thread it appears that the new pipes are a bit flattened, possibly restricting the flow?

cfaber oil pipes (640x640).jpg


Desperate straw-clutching........(I'm not familiar with the 'slab' oil tank but) are you certain that you have the pipes connected the right way round?

Oil. Crankcase unions..JPG
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Re: Wet sumping while running

Postby cfaber » Sat Dec 14, 2019 11:43 pm

Positive they're connected the right way around.
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Re: Wet sumping while running

Postby oldandsmelly » Mon Dec 16, 2019 9:28 am

A mate of mine had the same problem following an engine rebuild and went down the path of checking oilways etc with no clear improvement. In his case, the root cause turned out to be wear and scoring in the crankcase surface where the oil pump runs. This wear was very slight but enough to cause insufficient lift on the scavenge side. In his case, the damage had been caused by debris from a melted piston, but at first glance the damage didn't seem massive; just some light scoring.

The chap had his crankcase machined out where the oil pump runs and a thin walled phosphor bush inserted. There is an article somewhere on this site about how to do it (but I can't find it); my mate took this article and crankcase to a machine shop and they affected the repair and the bike now scavenges oil fine.

Of course, an identical problem doesn't mean the same root cause but if you run out of ideas it might be worth trying.

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Re: Wet sumping while running

Postby SPRIDDLER » Mon Dec 16, 2019 12:35 pm

I'm going off at a tangent here but it seems there's nowhere else left to go (and I'm really intrigued to know the cause :ugeek: ).
In your very first post in the other thread you wrote:

cfaber wrote:From what I could tell, the engine was seized,........

I'm debating whether or not to replace the piston, it's got some scoring on the lower side, but that's about it. The rings look brand new as they still have machining marks on them (|/\/\/\/|). I'm thinking that the PO might have replaced the rings at some point,.....

I also found that the cylinder itself is smooth as silk and likely was never honed after the ring job.

Are they the right rings, with satisfactory gaps?

In a recent reply you wrote:

• smoky exhaust
• oil level dropping in the tank
• oil belching out of the breather
• burned oil in the exhaust


These can also be due to excess c/case pressure from piston blow-by or (pretty unlikely) bad adjustment of the inlet valve metering screw. However, a build-up of two pints in the sump after 10 minutes would seem too much to blame on either of those issues.

Re. scoring of the plunger housing you only have 1 thou clearance which is within spec'n. From your photo there seems to be some scoring of the plunger (1 & 2) and possibly some minor damage to the plunger splines (3, 4, and 5) but it's not easy to judge from the photo. In any case it doesn't seem enough to worry about unless the damage is greater within the softer alloy plunger housing. At 6 there seems to be green algae...... :?

faber oil pump 3 (640x396).jpg
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Re: Wet sumping while running

Postby cfaber » Mon Dec 16, 2019 7:09 pm

SPRIDDLER wrote:I'm going off at a tangent here but it seems there's nowhere else left to go (and I'm really intrigued to know the cause :ugeek: ).
In your very first post in the other thread you wrote:


No worries, I'm stumped as well :)

SPRIDDLER wrote:
cfaber wrote:From what I could tell, the engine was seized,........

I'm debating whether or not to replace the piston, it's got some scoring on the lower side, but that's about it. The rings look brand new as they still have machining marks on them (|/\/\/\/|). I'm thinking that the PO might have replaced the rings at some point,.....

I also found that the cylinder itself is smooth as silk and likely was never honed after the ring job.

Are they the right rings, with satisfactory gaps?


Yes, the correct rings are fitted, with the correct gap. Compression is quiet good and the engine wants to start and run with little or no effort (after decompressing from TDC of course, otherwise I could stand on the kick stand)

SPRIDDLER wrote:In a recent reply you wrote:

• smoky exhaust
• oil level dropping in the tank
• oil belching out of the breather
• burned oil in the exhaust


These can also be due to excess c/case pressure from piston blow-by or (pretty unlikely) bad adjustment of the inlet valve metering screw. However, a build-up of two pints in the sump after 10 minutes would seem too much to blame on either of those issues.


How bad are we talking here? I have it on what I believe is correct (1/6 turn out from bottoming out)

SPRIDDLER wrote:Re. scoring of the plunger housing you only have 1 thou clearance which is within spec'n. From your photo there seems to be some scoring of the plunger (1 & 2) and possibly some minor damage to the plunger splines (3, 4, and 5) but it's not easy to judge from the photo. In any case it doesn't seem enough to worry about unless the damage is greater within the softer alloy plunger housing. At 6 there seems to be green algae...... :?


I noticed the wear as well, however it seemed that it was superficial (aside from the spline wear). The algae is the oil I'm using (50w Penn grade) which happens to be green =)
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Re: Wet sumping while running

Postby SPRIDDLER » Mon Dec 16, 2019 7:47 pm

cfaber wrote: How bad are we talking here? I have it on what I believe is correct (1/6 turn out from bottoming out)

That's fine. In fact the screw would probably have to be near falling out for the flow to be so troublesome. Even then it wouldn't pass two pints in ten minutes.

I noticed the wear as well, however it seemed that it was superficial (aside from the spline wear). The algae is the oil I'm using (50w Penn grade) which happens to be green =)

Understood.
My comments were mainly expressing my idle musings via the keyboard. Sometimes when puzzled and everything sensible has been checked I have found it pays to faff about in the shed thinking/checking the unlikely or downright silly during which investigations I may just by chance stumble across the cause of problem. In this case it hasn't :(
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Re: Wet sumping while running

Postby cfaber » Mon Dec 16, 2019 8:06 pm

No doubt, I don't mind one bit as I'm just as stumped so anything is worth looking at =)

The only thing I could think of as a possibility is a massive crack in the inside of the crank case in one of the oil gallery drillings, but I didn't see anything like that (as I probably would have noticed a massive crack)
Fix it until it's broken!

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