1958 G11 - Wet Sumping

Information relating to the Matchless G11 or AJS Model 30 600cc twin
starfield181
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1958 G11 - Wet Sumping

Post by starfield181 »


When I removed the primary drive inspection cap (alloy chaincase) a flood of oil came out; dirty black stuff which looked and smelt like used engine oil. With the flood cleaned up I reverted to the original plan and adjusted the over-tight primary chain.

Is excess oil in the chaincase a clear indicator of wet sumping or is there some other cause I should be investigating? For now I will be removing the crankcase drain plug between runs to measure the amount of wet sumping and checking the chaincase oil level at the same intervals.

Prev owner told me proudly that the bike never wet sumped and indeed I had not seen any evidence either in my very short period of ownership; no smoke from the exhaust nor huge puddles of oil on the floor on startup. The latter surprised me as there was at least 1/2 litre of excess oil in the chaincase yet only a few drops showing on the ground when parked after a short run. Perhaps one saving grace is that the chaincase is oil tight?


Incidentally, does the excess crankcase oil drain into the chaincase when stood or is it pumped there only when the engine is running.

Thanks

Peter
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dave16mct
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1958 G11 - Wet Sumping

Post by dave16mct »

It can drain into the chaincase if left on the side stand for some time. It can also be pumped into the chaincase if you top up the oil before starting up. Always start the bike and let it idle for a few minutes before checking oil level. Don't have too much oil in the chaincase. Just touching the bottom of the chain is enough. Dave.
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Malleon
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1958 G11 - Wet Sumping

Post by Malleon »

Firstly, Peter,
If you have slackened the primary chain, you will have tightened the main chain; do check the tension of this, which should have a vertical play of 1.1/8 inches when the machine is on the centre stand. Adjust this if necessary.
With regard to excess oil in the primary chaincase, this could be due to too much pressure in the crankcase. Is oil returning to the oil tank when the engine is running at around 1,000 r.p.m.? Remove the oil tank filler cap and check! This is a routine item when starting up.
The oil is returning:- is it black and very smelly? If so, time for a change.
Drain off oil from tank and crankcase.
Remove the crankcase oil filter and fit new replacement while tank is drained.
Then disconnect feed pipe at the tank end to find and remove the fine gauze filter, replace it if damaged, or clean it thoroughly in petrol before refitting.
Fill oil tank to the correct level with a good monograde SAE 50 oil.
Start the engine and check for return to the tank, let the engine'warm up'. If all is satisfactory stop the engine and let it stand for a couple of hours before examining the chaincase oil level. Please let us know your findings!
The engine is designed to operate on a "dry sump" system, so there should (in theory) never be 'excess crankcase oil'. Wet sumping is usually due to a worn oil pump or a sticking valve allowing oil to feed from the tank when the engine ain't running, and is a fault frequently mentioned on this Forum. If you enter 'Wet sumping' into the search box on the Forum Home page, you should find enough references to read and send you to sleep with your bedside light left on!
Good hunting.
starfield181
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1958 G11 - Wet Sumping

Post by starfield181 »

quote:
Firstly, Peter,
If you have slackened the primary chain, you will have tightened the main chain;
Understood and rear chain was adjusted at same time.

quote: With regard to excess oil in the primary chaincase, this could be due to too much pressure in the crankcase. Is oil returning to the oil tank when the engine is running at around 1,000 r.p.m.? Remove the oil tank filler cap and check! This is a routine item when starting up. The oil is returning:- is it black and very smelly? If so, time for a change.

The oil does return on startup steady stream initially settling to a slightly more intermittent stream after a minute or so, Would have said this was ok worked on my BSA anyway.

Engine oil looks quite clean and filter/oil change was reputedly done about 500 miles ago. Will do a further change soon but don't see this as an immediate priority until I have established if it is wet sumpimg. I plan to leave it with the crankcse drain plug removed to measure how much it wet sumps, would rather not be throwing new oil away. Thanks for the advice on the procedure though.

quote:
Fill oil tank to the correct level with a good monograde SAE 50 oil.

Prev owner has always run it on straight 40 (the winter recommendation). As we are heading into Autumn/Winter I wondered if 50 might be a bit thick and was planning to use 40 for now and a further change to 50 next spring. Would this be sensible or can you get away with 50 all year

quote: If you enter 'Wet sumping' into the search box on the Forum Home page, you should find enough references to read and send you to sleep with your bedside light left on! Good hunting.

I had tried that search and yes I did get a shedload of posts to look at. Trouble is trying to find one that covers your own issues which is why I decided to post descibing my actual situation. To some extent its a bit like reading a medical book, you begin to imagine your bike has all sorts of ailments.

I will do some more tests and report back my findings

Peter
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Malleon
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1958 G11 - Wet Sumping

Post by Malleon »

Hello again, Peter,
The only reason I suggested an oil change was because you described the chaincase excess as being 'black and smelly'. It is possible for gearbox oil to enter the chaincase if the shaft oil seal is kaput, but that shouldn't be black either, and your clutch plates would be affected.
My own '58 G11 would wet-sump if left unused for a month or more, so I fitted a shut-off valve in the oil feed line (protected with a magneto cut-out), and this solved my problem.
Straight SAE 40 is a good choice for all-year use, the reason I use 50 in summer (???) and 30 in winter is to encourage my lazy brain to remind me to change the stuff more frequently than I otherwise would!
I apologise if I have insulted your knowledge of these old lumps, but you didn't tell whether you had 'previous' as they say in constabulary circles; I now know that you have.
Keep us informed, please.
Best regards.
Cerberus
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1958 G11 - Wet Sumping

Post by Cerberus »

For what it is worth, I've had problems on my G9 with it filling the chaincase. After about 200 miles of steady driving at about 45-50, the chaincase fills up to the level of the inspection cover and starts to leak out the back and spray the back wheel.

It wasn't wet sumping. Sat it for several weeks with drain plug out, very little emerged.

What it was (and may still be - see later), was when the engine was working hard, it was blowing a small amount of oil out of the breather in the end of the crankshaft. I actually rode the bike for about 6 miles with a dry clean chaincase and examined where the oil was coming from.

After lots of headscratching, consulting the gurus in the local section and a lot of reading, we suspected slightly worn rings increasing crankcase pressure, (this is one of the suggestions in the "red book").

However, not long after fitting new rings (the gaps were at the limit), I had a senior moment, forgot the oil tap and threw a con rod. The engine rebuild is now almost complete (including replacing the 1950 crankshaft, fitted to the 1956 crankcase)! So no definitive answer but it is one of the options.
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bigwol
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1958 G11 - Wet Sumping

Post by bigwol »

"The oil does return on startup steady stream initially settling to a slightly more intermittent stream after a minute or so" ......

This would indicate there is more oil on start up to scavenge than is there during normal running, sounds a lot like wet sumping to me.
My '31 only leaks into the chain case if left for a while, starting up at least once a week prevents it.
It's all just riding motorbikes
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saltbox alf
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1958 G11 - Wet Sumping

Post by saltbox alf »

quote: TextTo some extent its a bit like reading a medical book, you begin to imagine your bike has all sorts of ailments. I find that very true especially when jumping up n down on the kickstart after flooding the bike, I wonder what ailments I have, what will give out first lungs ,heart or ankle
It's the black and dirty look to the oil that is a worry, mentioned earlier blowing by the breather, this a strong posibility as the combustion process will blacken oil quickly with an excess blow by the rings. worth a comprssion check as well as what else your doing
Allons-y, amis de Matchless et AJS
starfield181
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1958 G11 - Wet Sumping

Post by starfield181 »

quote:
Hello again, Peter,
The only reason I suggested an oil change was because you described the chaincase excess as being 'black and smelly'.


Sory Malleon, you are quite right, I did lead with my chin on this one. What I was comparing it with was the normal contents of a primary chaincase which is usually much the same colour as it came out the can and free from combustion contaminents. The engine oil will benefit from a change but I don't think its so bad as to be an immediate priority.

I have made some diagnostic progress today. Having left the bike standing overnight; the chaincase level had not moved even though 175ml of oil was subsequently drained from the crankcase. I measured the level in the oil tank then ran the engine for a while until the level in the tank had stabilised (it dropped about 10mm). Crankcase was drained again and I collected 75mm of oil this time so I assume this is the steady state content of the crankcase and anything above that will be due to wet sumping. Chaincase still at same level. I now plan to drain the crankcase every day at the same time for a few days to assess the rate of wet sumping.

Does anyone have any idea how much oil needs to be in the crankcase before it starts to be pumped through to or drain into the chaincase.

Many thanks

Peter
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Malleon
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1958 G11 - Wet Sumping

Post by Malleon »

Sorry, Peter, I can't answer that one as I've never been so afflicted!
dave16mct will know, though, I'm sure; he's
more experienced than I am.
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