Wet sumping

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Chris Berry
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Wet sumping

Post by Chris Berry »

Hi,
This morning when I went to start my bike, which has now done 250 miles from rebuild, it billowed blue smoke. Upon checking the oil reservoir it was substantially lower than usual. I then drained about 300 ml from the sump. Is this wet sumping indicative of a worn pump. I am asking this as I replaced the plunger on rebuild and this is the first time it had happened to me. The pump is still pumping to the head and to the oil tank.

Regards
Chris
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Rob Harknett
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Re: Wet sumping

Post by Rob Harknett »

The sump does retain a certain amount of oil, not sure how much in ml. As you have done work on the pump. Perhaps someone will suggest you may have done something wrong and advise accordingly. I have never had a pump problem, so do not have any experience to pass on. Except having to except, when standing for a few weeks, my bikes will sump oil. So all I do is drain and re start.
SPRIDDLER
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Re: Wet sumping

Post by SPRIDDLER »

Chris Berry wrote:Hi,
This morning when I went to start my bike, which has now done 250 miles from rebuild............,
How long had it been standing since last run?
'There is a tide in the affairs of men
Which taken at the flood............'
Chris Berry
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Location: QUEENSLAND AUSTRALIA

Re: Wet sumping

Post by Chris Berry »

SPRIDDLER wrote:
Chris Berry wrote:Hi,
This morning when I went to start my bike, which has now done 250 miles from rebuild............,
How long had it been standing since last run?
No more than 24 Hrs as I was working on it the day before. I've checked the pump operation which seems OK. Tonight I drained the sump completely and I'll See how much is in it tomorrow morning (Australian time)
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Rob Harknett
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Re: Wet sumping

Post by Rob Harknett »

If you refilled with oil, upon starting the sump will first fill to the required level, so oil level in the tank will drop a bit. The bike should not smoke a lot. Need to know the history, perhaps oil circulation is actually OK and some thing else done when you worked on the engine is causing the engine to smoke.
SPRIDDLER
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Re: Wet sumping

Post by SPRIDDLER »

Chris Berry wrote:I replaced the plunger on rebuild and this is the first time it had happened
Hmm, that's a bit quicker than it 'should' be after only 24hrs.
Your new pump plunger for the '48 should have the 1/4" annular groove for the plunger guide pin. A 3/16" groove was used in the earlier (up to '46/'47?) engines.
I suppose you haven't re-used a 3/16" pin in a 1/4" plunger, thus reducing the pump throw and therefore its efficiency?
Otherwise check that the pump end plates are sealing 100%.
'There is a tide in the affairs of men
Which taken at the flood............'
Chris Berry
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Posts: 83
Joined: Fri Sep 16, 2016 7:51 am
Location: QUEENSLAND AUSTRALIA

Re: Wet sumping

Post by Chris Berry »

SPRIDDLER wrote:
Chris Berry wrote:I replaced the plunger on rebuild and this is the first time it had happened
Hmm, that's a bit quicker than it 'should' be after only 24hrs.
Your new pump plunger for the '48 should have the 1/4" annular groove for the plunger guide pin. A 3/16" groove was used in the earlier (up to '46/'47?) engines.
I suppose you haven't re-used a 3/16" pin in a 1/4" plunger, thus reducing the pump throw and therefore its efficiency?
Otherwise check that the pump end plates are sealing 100%.
Another lesson i guess. I have just reused the old guide pin but it did seem to fit well in the groove of the plunger. The engine in my bike is actually a '51' but i'm not sure what difference that makes to the oil pump. On a better note I checked the oil tank this morning and there was no appreciable drop in oil level and the sump was empty (I drained it last night). When I started the bike there was no smoke so who know what it was. Maybe the pump plunger was in such a position that the oil was allowed to run through the pump into the sump.
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Pharisee
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Re: Wet sumping

Post by Pharisee »

Chris Berry wrote:Maybe the pump plunger was in such a position that the oil was allowed to run through the pump into the sump.
There was popular myth that you should leave the engine at TDC on the compression stroke to avoid wet sumping but when you think about it, with eight revolutions of the crankshaft for one cycle of the pump, you've only got a one in eight chance of it being the 'right' TDC :D
I'm from the Fens.... Gimme six.
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Expat
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Re: Wet sumping

Post by Expat »

Mmmm.......didn't think of that. ;) Still, it is possible to relax the valve springs at TDC on the firing stroke, eh?
Luckily wet sumping is not a problem for me, yet anyway! :)
Keep shiny side up.

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clive
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Re: Wet sumping

Post by clive »

Chris Berry wrote:
SPRIDDLER wrote:
Chris Berry wrote:I replaced the plunger on rebuild and this is the first time it had happened
Hmm, that's a bit quicker than it 'should' be after only 24hrs.
Your new pump plunger for the '48 should have the 1/4" annular groove for the plunger guide pin. A 3/16" groove was used in the earlier (up to '46/'47?) engines.
I suppose you haven't re-used a 3/16" pin in a 1/4" plunger, thus reducing the pump throw and therefore its efficiency?
Otherwise check that the pump end plates are sealing 100%.
Another lesson i guess. I have just reused the old guide pin but it did seem to fit well in the groove of the plunger. The engine in my bike is actually a '51' but i'm not sure what difference that makes to the oil pump. On a better note I checked the oil tank this morning and there was no appreciable drop in oil level and the sump was empty (I drained it last night). When I started the bike there was no smoke so who know what it was. Maybe the pump plunger was in such a position that the oil was allowed to run through the pump into the sump.
Unless your 51 engine has been bodged it must have had the later pump and hence the later guide pin. My usual advice at this point is did you disassemble the guide pin? It has one end which is relieved and smaller than the other. That end must go into the pin holder, although it looks like it should be the other way round. If in the wrong way it will be a loose fit in the pump groove and will substantially reduce the effectiveness of the pump. I am just wondering if instead of wet sumping the reduced effectiveness of the pump meant the return side was not coping quite wth the supply and hence the sump filled gradually over the 250 miles of use.
So is it possible you have it in the wrong way? If you are going to check you will have to drain the oil tank as the pump body will tend to slide forward as soon as you take the pin out. You need the end plates off to relocate the pin in the groove. Still after 250 miles on a rebuilt engine an oil change would not be a bad thing.
clive
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