Can't keep the oil in

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Can't keep the oil in

Postby Locust » Wed Aug 27, 2008 11:36 am

Hi everyone it's Locust again.

This time I am desperate, after getting over the clutch problem thanks to certain members (thanks) I have desided to sell the G2 CSR but I can't stop it eating oil. so can't sell it in that state.

Thought I had the answer yesterday the oil filter was the type with the felt round the outside and that was blocking the return so the oil was gathering in the crankcase and getting up the bore and being blown out the exhaust, so I thought.???

Took the filter out and run the engine with no filter guess what it's still pumping the oil out the exhaust, So over to the forum what in earth is the problem chaps I'm stumped.

Please help or make me an offer for the bike.???

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Can't keep the oil in

Postby model26 » Wed Aug 27, 2008 12:48 pm

It will most likelyl require a re-bore and new piston + rings.

As you are selling and as a quick fix, you may get away with just re-honing the bore and new rings.

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Can't keep the oil in

Postby Locust » Wed Aug 27, 2008 2:41 pm

Hi 26

It has a new piston and bore that is not the problem. any other thoughts.???

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Can't keep the oil in

Postby paul knapp » Wed Aug 27, 2008 2:49 pm

Are you sure it doesn't need a good run to dry out the over oiled internals?

Paul
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Can't keep the oil in

Postby Groily » Wed Aug 27, 2008 5:54 pm

I think the piston and or bore are the most likely problem unless you have some amazing lubrication system for the rockers which is filling the head with gallons of the black stuff, or the engine is not scavenging and therefore filling with oil (as it would with the blocked filter you mention). If it's literally pumping oil out of the exhaust, it's probably because said oil is being pumped up the bore and out of the valve. Stuck rings could do it. Are you sure the piston rings are the correct height f0r the grooves?? I know it sounds daft, but if they are able to move appreciably up and down in their grooves, you'll have a pump on your hands. It happened to me years ago when I'd rebuilt a twin, before there were good people like JSL to make sure the right bits went with the right bits. I should have noticed, but one foolishly trusts people sometimes when they sell you stuff!

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Can't keep the oil in

Postby Locust » Thu Aug 28, 2008 11:17 am

Gr (oily)
Thats my problem excuse the pun.

With a new piston I assumed the rings to be correct, so I don't think that is the problem.

The return is coming back into the tank now, without the filter in place.

If all the oil were filling the rocker box surely that drains back into the crankcase via the pushrod tube, the valves and guides were new so I would not expect any oil getting down that way.

The engine runs fine but the oil burning affects it, Then I get the white fog out the exhaust which is worse than a two stroke.

The oil pump seems to be working well and I am getting a return but the oil leval goes down quite quickly.

Someone must know the reason.??????

Locust

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Can't keep the oil in

Postby itma » Thu Aug 28, 2008 12:12 pm



The oil level should not drop markedly.
Even though you have a return It seems to me that the return is not working properly,ie not scavenging, and the sump is filling with oil,and being pumped up into the combustion chamber.
As this bike has an integral oil tank it must be a problem with the pump itself or internal oil ways?
Was the engine assembled with an excess of sealant which is blocking an oil way? or something dropped into the case when the barrel was off?
Short of taking it all to bits, I am at a loss for suggestions.

Edited by - itma on 28 Aug 2008 12:16:01 PM

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Can't keep the oil in

Postby Groily » Thu Aug 28, 2008 12:27 pm

Well, the pump seems to be delivering oil in both directions, but the unwanted auxiliary pump is sending it out for the benefit of following traffic.

If you take the exhaust pipe off at the head, the exhaust port will be literally dripping in the stuff, and the pipe will be full of slime that will start to bake on and cause it to smoke for a while even after it's fixed.

I do not know one end of a G2 from the other. However, an engine's an engine! This is not a complicated one, and the probable causes are limited to:

Oil circulation or Breather problems, which you seem to be able to rule out now. (I well remember a friend's Triumph 5TA which did just what you're doing - because the return oil pipe was kinked inside the tank and only letting a dribble back. We all got the rest of it if we were daft enough to be behind him!); or

Piston/bore trouble - stuck rings, all ring gaps in a line rather than equally-spaced, rings that move vertically in their grooves, compression rings (if they are tapered?) fitted the wrong way up, wrong oil control ring, or extreme wear in the bore. Even the wrong size piston.

I just recently had exactly the same problem with another marque, a 350 single bought unseen. It pumped everything straight out the back door. And then stopped when it literally drowned because the oil couldn't drain away as fast as it was sent up. The previous chap had used the wrong piston (among other horrors), from another marque altogether, with no oil control ring. You obviously haven't got anything that stupid going on, but you clearly have something badly amiss and if the engine breathes and the oil goes round, I remain nervous in the piston department and would at least get the cylinder off to prove all is well.

I'd also, as you get this resolved, pay very particular attention to the cleanliness of the exhaust valve stem and guide - because a fried-on layer of oil is a prime cause of stiction as I discovered with my recent oiler, with possibly dire consequences for cam follower, pushrod and rocker.

I can't think of anything else - but maybe G2 gurus have a ready explanation . . .

Best of luck.

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Can't keep the oil in

Postby Biscuit » Thu Aug 28, 2008 5:31 pm

When I followed you on a short run, your exhaust was clear, if rather loud, so what has happened? I may have misunderstood at the time, but I thought you said you had bored the cylinder youself, could it be the finish? I had a conversation with a chap in Kent who rebores cylinders, and he leaves them relatively rough, his theory being running in is when you need good oil retention in the bores, Why not have a peep at the ring gaps?.




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Can't keep the oil in

Postby Locust » Thu Aug 28, 2008 8:16 pm

Hi Alan
Nice to hear from you.
When you came over that time I still had the fog problem but we also had tick over problems.
Now the engine is running fine until it gets oil bound.
I have changed the barrel because my rebore was rubbish (chatter marks) I kept my new piston and used what I thought was a good bore.
I can't beleive that a bore and piston could give me this problem alone.

Your thoughts are appreciated, keep thinking.

Locust

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