1958 G11 - Wet Sumping

Information relating to the Matchless G11 or AJS Model 30 600cc twin
wilko
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1958 G11 - Wet Sumping

Post by wilko »

It has to rise to the level of the mainbearings before it gets into the chaincase.
Ninetoes
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1958 G11 - Wet Sumping

Post by Ninetoes »

When I bought my M30 three years ago it had been standing untouched for more than 3 months. Before I even tried to start it, I decided to drain the crankcase, knowing of the propensity for wet sumping.

I drained off exactly 3/4 of a pint which is the normal residual quantity after normal use, once it has drained from the engine. So Iknew I didn't have a problem with wet-sumping. I did, however have a problem with a stripped thread on the drain-plug hole, so the whole engine came out and was rebuilt in my workshop, with various other minor faults being corrected along the way.
It now runs very sweetly, no smoke, minimal oil consumption, and no leaks!
starfield181
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1958 G11 - Wet Sumping

Post by starfield181 »

I checked the measuring jug just now, about 30 hours since I last drained the crankcase and there was nearly 200ml of oil present. The old posts on the subject don't seem to give guidelines on the scale of leakage but I am assuming that mine would be at the high end and warranting some treatment. No wonder the chaincase was full of oil; cannot believe that the previous owner thought this bike was free of the wet sumping probem!.

Anyway I am now at the stage of what to do.

Short term I am probably going to have to run the engine every day and while the weather is fine I can also go for a ride.

Medium term possibly identify a satisfactory tap with bullet proof safety features; does such a thing exist?

Longer term investigate and cure the wet sumping. My understanding is that the oil leaks through the spindles of the feed gear. Guess it would also leak from the scavenge gear but only to the extent of the oil in the pipe, is this significant or can it be ignored? Does rebuilding the pump(s) actually cure the problem or simply reduce its effect. Given that I will likely need to remove the timing cover shortly anyway to adjust the ign timing (see post on adv/ret lever). maybe it would be best to go for this sooner anyway.

Have I missed any obvious options and can anyone give an indicator of costs for the above solutions. My inclination is to fix the problem rather than deal with the symptoms unless there is a huge cost difference.

Sorry, should have mentioned that the engine is believed with good reason to have covered 36500 miles. It has never been apart and seems in generally good health, no smoke (even with a sump full of oil), or abnormal noises, starts easily, runs nicely and is a pleasure to ride.

Thanks

Peter

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dave16mct
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1958 G11 - Wet Sumping

Post by dave16mct »

Hi Peter, are you sure you need do anything at all? 200ml sounds about right to me, about a cupfull? There's always some oil in the sump. OK if it keeps on draining down it becomes a problem, but this doesn't seem too bad.
Anyway, to answer your question, it doesn't leak much from the scavenge spindle,only from the feed gear spindle. You can make a plate to cover this. You would be best to find the article in the jampot by Ray Stringer a few years back. he explains in some detail all the causes of wet sumping and the cures. Or you could just ride it more, you wouldn't have any problems with wet sumping then! DaveEdited by - dave16mct on 09 Sep 2012 9:02:17 PM
ghost123uk
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1958 G11 - Wet Sumping

Post by ghost123uk »

quote:
Peter wrote :-

I checked the measuring jug just now, about 30 hours since I last drained the crankcase and there was nearly 200ml of oil present.


I note further up you drained the normal "drain down" that any engine does after first turning off, before you test measured the actual wet sump product. Was this 200ml (quouted above) excluding normal drain down ? If you had drained before leaving it for the 30 hours, I would say it was too much. (and I commend your methodical approach ) I did measure mine too, it was much less than that, but my "methodical" testing omitted actually noting down the quantity I did however determine that it was OK as long as I ran the motor at least once a week !

I too wish to cure the issue rather than mask the symptoms with a tap (I did get one but decided not to fit it = anyone want it ?)

For now, as I intend to mothball mine (G12) come the winter, I will simply drain the tank.
~~~~~~~~~~~~~~~~~~~~~~~~~~~

John, with a G12, near Chester in the UK
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bigwol
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1958 G11 - Wet Sumping

Post by bigwol »

A hand vacuum pump will suck the oil out and deposit into a container just as easily. Although not something i've done as yet it has been recommended to me by a few more experienced oiwners!
It's all just riding motorbikes
starfield181
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1958 G11 - Wet Sumping

Post by starfield181 »

Thanks for various replies and it seems that I have probably confused people over my 'methodical' approach to measuring the degree of wet sumping. The table of events is as follows:

1st Drain of crankcase yielded 175ml. Not sure how long it had been standing at this point but the bike had done a run the previous day so not more than 24hours.

2nd drain yielded 75ml which was immediately after the engine was stopped having been run for 10 minutes or so. The crankcase was empty at the start of this test having just done test 1 and it was meant to establish the amount of oil in the crankcase during normal running,

3rd Drain yielded near 200ml after a period of 30hours. The crankcase was empty at the start of this period having just done test 2. Engine was not run between test 2 and 3

4th drain - today yielded 50ml after a period of 24hours. The crankcase was empty at the start of this period having just done test 3. Engine was not run between test 3 and 4

What puzzles me is that the rate of wet sumping seems to have slowed from Niagra proportions to virtually nothing. The only obvious explanation (to me anyway) is that the major part of the leakage is from the scavenge side of the oil pump and stops once the return pipe has drained down completely. Did not think there was that much oil in the return pipe though.

I will measure it again tomorrow.

On a wider issue, I read in past post about making up plates to blank of the spindles. This seems like a good and reasonably simple idea. Unfortunately I could find no details about how to do it. Can anyone point me to more info on this subject and is there any known down side to this solution.

Peter
starfield181
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1958 G11 - Wet Sumping

Post by starfield181 »


quote:
Thanks for various replies and it seems that I have probably confused people over my 'methodical' approach to measuring the degree of wet sumping. The table of events is as follows:

1st Drain of crankcase yielded 175ml. Not sure how long it had been standing at this point but the bike had done a run the previous day so not more than 24hours.

2nd drain yielded 75ml which was immediately after the engine was stopped having been run for 10 minutes or so. The crankcase was empty at the start of this test having just done test 1 and it was meant to establish the amount of oil in the crankcase during normal running,

3rd Drain yielded near 200ml after a period of 30hours. The crankcase was empty at the start of this period having just done test 2. Engine was not run between test 2 and 3

4th drain - today yielded 50ml after a period of 24hours. The crankcase was empty at the start of this period having just done test 3. Engine was not run between test 3 and 4



5th Drain (Tuesday 11th Sept) yielded 25ml. Engine still has not been run. Giving it one more day then going to take the bike for a run and repeat the tests.
starfield181
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1958 G11 - Wet Sumping

Post by starfield181 »

quote:
A hand vacuum pump will suck the oil out and deposit into a container just as easily. Although not something i've done as yet it has been recommended to me by a few more experienced oiwners!


Hi Bigwol, you have lost me somewhat. Cannot see how you could use a vacuum pump to drain the oil from the crankcase on a G11. Would be quite useful if you could. Peter
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bigwol
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1958 G11 - Wet Sumping

Post by bigwol »

I meant drain the oil from the tank Peter to prevent wet sumping when the bike is laid up.
It's all just riding motorbikes
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