G9 Dynamo oil leak/chain case oil leak

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JasonHar1
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Posts: 20
Joined: Sun Jul 10, 2011 12:39 am
Location: DEVON UK

G9 Dynamo oil leak/chain case oil leak

Post by JasonHar1 »

Sorry if I've missed some vital info on the forum for this. I've read so much and I've been going round in circles.

I've got a 1952 G9 which has always had the chain case oil leak fitted as standard. I recently fitted the new style 'T' profile gasket with a silicon based gasket seal to the chain case which cured the leak. 30 miles or so later, the dynamo gasket started leaking and more than just a drip. I've replaced the dynamo gasket and it's blown again straight away.

I've tested the compression and both cylinders are the same, around 120 which seems reasonable, so I think I can rule out piston ring issue causing pressure in the crankcase.

I was pointed in the direction of the petal valve on the crank shaft which I've removed and appears to be working correctly. I can blow through it and feel it open.

Is it possible that in sealing the two halves of the chain case together that I've caused a build up of positive pressure in the chain case that has blown the dynamo gasket? I thought there was a gap around the clutch on the inner chin case which would stop this but it's not clear to look at. If it's possible, could I remedy it by drilling a hole through the inner chain case, near the top? Or am I barking up the wrong tree? The dynamo seal has been good for a while, I am confident in replacing it and I do not readily believe that it leaking now is a coincidence and not related to me sealing the chain case.

I am confused. Any help would be appreciated.

Jason
Jason

1952 Matchless G9 Super Clubman, 2014 Triumph Street Triple, 2007 Suzuki 1250 GSF Bandit.
lawrence
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Joined: Mon Jan 01, 2001 12:00 am
Location: NORTHAMPTONSHIRE UK

Re: G9 Dynamo oil leak/chain case oil leak

Post by lawrence »

Hi Jason. If you search Alan Jacobs posts you will find one describing how to perfectly seal the pressed steel chaincase (which I presume you have?).

If your dynamo seal is blowing that quickly it must be excess crankcase pressure. Once pressure escapes into the primary it can easily escape through the gearbox shaft hole so you wouldn't have a build of pressure there. I had a similar problem for a long time and removed the crankcase flap valve several times but it blew back and forwards nicely so I thought it ok. On removing it for a fourth time I discovered it stuck closed. After freeing it, it worked nicely again but as I rotated it I discovered it stuck in a particular location. Some of these valves are dismantlable but if not they aren't dear. I put a new one on mine and it cured the problem.
JasonHar1
Member
Posts: 20
Joined: Sun Jul 10, 2011 12:39 am
Location: DEVON UK

Re: G9 Dynamo oil leak/chain case oil leak

Post by JasonHar1 »

Thanks Lawrence,

I'll order a new valve, it's not worth the hassle of repeatedly splitting the chain case if it could have an intermittent or hard to spot fault. I did run the engine with the chain case off and I couldn't detect anything to suggest the valve was working.

Also, I did read the post about sealing the chain case and it worked extremely well. Hopefully, I can repeat that with the practice I've now had.

One thing that may be worth sharing, I used the new 'T' shape profile foam/rubber gasket on the chain case and after cutting it to length I super glued the ends together which made fitting it much easier. It then held itself in position much better for the reassembly.

Jason
Jason

1952 Matchless G9 Super Clubman, 2014 Triumph Street Triple, 2007 Suzuki 1250 GSF Bandit.
Flash
Posts: 438
Joined: Mon Jan 01, 2001 12:00 am
Location: KENT UK

Re: G9 Dynamo oil leak/chain case oil leak

Post by Flash »

Jason.
I fitted one of the new style chain case rubbers on my G9 but it still leaked, so I cut an old push bike inner tube and put around the outside, I'm not sure how successful it is as I have not been out on it since but I am hoping it's now okay.

John
g5wqian
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Location: near swindon wilts

Re: G9 Dynamo oil leak/chain case oil leak

Post by g5wqian »

i used the clubs modified seal and use no sealant and it doesnt leak .

i have rebuilt my dynamo and fitted new oil seal and cork seal and refitted dynamo ,all ok .

on the rear half of the primary chaincase i have sealed around the mounting holes so it wont leak out of those , plus on the crank the oil throw out ring spacer was not fitted right and had a gap allowing it to move 1/4" back and forth , so now has the spacer fitted the right way and the oil thrower does its job and stays in the end of the crankcase half .

i do have a small oil leak out from under the bike but it isnt the primary chaincase , although you might think it is , but it is actually originating from the kickstart shaft hole in the gearbox . .

i did find that previous owner had fitted an o-ring to end of dynamo and silicone sealant , this did leak but after i rebuilt the dynamo and used original style cork seal and welseal sealant it seems fine although after fitting dynamo and tightening the various clamp and bolts i left it overnight to allow the welseal to go off .

the join of the ends of the rubber seal on the chaincase i put right at the top middle of the chaincase and no sealant on it or its ends , it is a little fiddly to fit the seal in place and get the alloy band etc round it and pulled up without anything coming out of place but if i can manage it anyone can .

hope some of this might prove useful to read
all the best
ian
JasonHar1
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Posts: 20
Joined: Sun Jul 10, 2011 12:39 am
Location: DEVON UK

Re: G9 Dynamo oil leak/chain case oil leak

Post by JasonHar1 »

I contacted the club for a new crankshaft valve and they informed me the company that made them has ceased trading and they didn't have any left. After other dead ends I phoned AMC spares whose number I'd had on a post it for a few years and they had a new valve. I duly purchased it and fitted it and tested it with the front chain case off. Immediately, I could see a difference. When I kicked the engine over a small amount of oil was spat out of the valve, a similar amount came out when I stopped the engine running. This hadn't happened with the old valve, so I suspected I was on to something.

I refitted the chain case with a new 'T' profile gasket, which I again cut to length and super glued the ends together. After three rides totaling about 100 miles, I'm happy to say that the problem appears to have been solved. I do have a very small oil leak which produces a few drips of oil after a 30 mile run, which drip from the bottom of the sump behind the sump plug but it is insignificant and I don't think it's coming from the chain case.

In any case, it's the tidiest that she's been running in many years and I'll take that.
Jason

1952 Matchless G9 Super Clubman, 2014 Triumph Street Triple, 2007 Suzuki 1250 GSF Bandit.
SPRIDDLER
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Re: G9 Dynamo oil leak/chain case oil leak

Post by SPRIDDLER »

Excellent! And thanks for the information. All updates are appreciated and useful.
'There is a tide in the affairs of men
Which taken at the flood............'
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