Chaincase filling with oil

Information relating to the Matchless G12 or AJS Model 31 650cc twin
MalcW
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Chaincase filling with oil

Post by MalcW »

Hi all. I friend who is new to classic bikes gave me a call yesterday to see if I could give him a hand to get his new AJS 650 twin started. I popped down and we got that sorted pretty quickly - just a fuelling problem. But we then found that it seems to be pumping oil into the crankcase, overfilling it and then leaking from behind the clutch. I took the gauze/felt filter out and it was pretty cruddy. We wiped off the excess muck and it's currently sitting in a tub of petrol.

Could that have been causing the issue, or should we be looking somewhere else? It's a '59 (I think) alternator version. I haven't had this problem with my '60 mag/dynamo version, so this is new territory for me. Mine has no felt on the filter, just gauze, and a separate cartridge oil filter.

Thanks,

Malc
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Re: Chaincase filling with oil

Post by SPRIDDLER »

Had he ever managed to start it? For how long had it been standing unused? Was the zorst smoky initially on start-up? If it had been unused for a week or more (the length of time varies bike to bike) the first thought must be that it could have wet sumped.
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MalcW
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Re: Chaincase filling with oil

Post by MalcW »

Hi Spriddler

Once we had sorted out the starting issue it started quite readily, with no obvious smoke from the exhausts. It had been stood for about 3 weeks though, and I must admit it didn't occur to me to pop the drain plug out and see how much was in there.

Oil certainly ended up in the chaincase though. Perhaps it's worth putting the filter back in, taking out the sump plug to make sure it's clear, bringing the chaincase oil down to the right level,and then taking it for a run to see what happens.

Malc
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Re: Chaincase filling with oil

Post by SPRIDDLER »

Twins are not my thing, Malc, so others will be able to offer more from experience, but it's worth a try and simple enough to do.
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Rob Harknett
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Re: Chaincase filling with oil

Post by Rob Harknett »

My twin sumps oil which also gets in the chain case. I just fitted a tap to stop it. Other bikes also sump oil but only in the engine, much easier to drain off after standing. I do have the oil filter in my twin. I do not think draining the twin sump will also drain the chain case. If anything, it will only drain down to the bearing level, still leaving the chain case above the level that should be.
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Re: Chaincase filling with oil

Post by SPRIDDLER »

Rob Harknett wrote:I do not think draining the twin sump will also drain the chain case. If anything, it will only drain down to the bearing level, still leaving the chain case above the level that should be.
I'm pretty sure that's what Malc said he'll do....... :?
MalcW wrote:........ taking out the sump plug to make sure it's clear, bringing the chaincase oil down to the right level, and then taking it for a run to see what happens. ...
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Rob Harknett
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Re: Chaincase filling with oil

Post by Rob Harknett »

SPRIDDLER wrote:
Rob Harknett wrote:I do not think draining the twin sump will also drain the chain case. If anything, it will only drain down to the bearing level, still leaving the chain case above the level that should be.
I'm pretty sure that's what Malc said he'll do....... :?
MalcW wrote:........ taking out the sump plug to make sure it's clear, bringing the chaincase oil down to the right level, and then taking it for a run to see what happens. ...
eeem. I'm sure oil gets in the chain case through drive shaft bearings. If oil gets out the chain case back in the engine to drain out the sump plug, it will only be down to bearing / drive shaft level. The chain case level is much lower. So the chain case will stay half full. Not at the reg'd level, at about the bottom run of the primary chain. Or is there a chain case drain plug. I'm not at all familiar with alloy chain cases. Just a note. When my twin sumped oil while standing, the new clutch plates stuck together, so more new plates had to be fitted.
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ajscomboman
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Re: Chaincase filling with oil

Post by ajscomboman »

Rob, Malc's wording implies he's going to drain the sump, lower the level in the chaincase by either draining or sucking the excess out with a syringe possibly and then going for a ride once that's been done.
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Re: Chaincase filling with oil

Post by SPRIDDLER »

ajscomboman wrote:Rob, Malc's wording implies he's going to drain the sump, lower the level in the chaincase by either draining or sucking the excess out with a syringe possibly and then going for a ride once that's been done.
Yep, that's how I understood it:

Replace filter
Drain chaincase.
Reduce chaincase oil level.
Go for a ride.

...........quite a long one apparently. ;)
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Rob Harknett
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Re: Chaincase filling with oil

Post by Rob Harknett »

SPRIDDLER wrote:
ajscomboman wrote:Rob, Malc's wording implies he's going to drain the sump, lower the level in the chaincase by either draining or sucking the excess out with a syringe possibly and then going for a ride once that's been done.
Yep, that's how I understood it:

Replace filter
Drain chaincase.
Reduce chaincase oil level.
Go for a ride.

...........quite a long one apparently. ;)
Thanks Rob. I combined actions 2 & 3 ( I noticed Neville has as well, he he ) I got lazy years ago when I got water in a chain case, made the oil go frothy. I sucked it out with a bike pump. Wonder if we will get to know what happened on the ride???
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