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Oil laek from dynamo gasket

Posted: Mon Jun 03, 2019 5:25 pm
by Keithwainwright
I have had my 650 huntmaster a while now and have just finished rebuilding the engine and it runs spot on ,starts first kick ticks over nice and revs freely with no smoke or burning oil . I left it to stand for about six weeks and drained the oil from the crank before starting as the oil had disappeared from the oil tank ,it wasn't on the floor so must be in the sump. It still runs good but now I have a leak from the dynamo cork gasket. How can this be ? .If it got in this space where the chain is how can it drain back. I cant see how it can get in or out . Can I drill the bottom of this cavity to let it drain on to the pump area . Any info is usefull thanks

Re: Oil laek from dynamo gasket

Posted: Mon Jun 03, 2019 5:59 pm
by Mick D
Hi
It might be just coincidence - reseal the dynamo cork and see what happens.
Regards Mick

Re: Oil laek from dynamo gasket

Posted: Mon Jun 03, 2019 7:25 pm
by Keithwainwright
I don't see how oil is supposed to be in this cavity at all .If I look at the gasket the part of the outer and inner cover creates a cavity for the chain and two sprockets to run and this appears to be separated from the other cavity's. Thanks for the input

Re: Oil laek from dynamo gasket

Posted: Mon Jun 03, 2019 7:34 pm
by Mick D
Hi
Hot grease, the recommended chain lubrication, can manifest as oil.
Regards Mick

Re: Oil laek from dynamo gasket

Posted: Mon Jun 03, 2019 9:41 pm
by Simon.Gardiner
Keithwainwright wrote:I don't see how oil is supposed to be in this cavity at all .....

Apparently it can come through the idler pinion bush. The 'proper' idler bush for the timing cover is different to the other idler/camshaft bushes as it has a 'return thread' cut into the end of it to work oil back into the timing chest. Maybe it's not 100% effective.
Also I've seen a few covers where the 'ordinary' bush (without the thread) has been used instead, so maybe it's not actually that necessary!
And as Mick says, your 'oil' may be more to do with what's been happening to the grease.....

SG

Re: Oil laek from dynamo gasket

Posted: Tue Jun 04, 2019 8:05 pm
by malcolm.johnson
I do not know about Huntmaster engines, but the BSA pre unit twins use a cork washer which is slightly compressed under the dynamo drive sprocket for the dynamo chain, to seal the only source of oil. Very similar engines. None of any of my BSA twins ever had that chamber fill with oil.

Re: Oil laek from dynamo gasket

Posted: Mon Jun 24, 2019 8:00 pm
by Keithwainwright
Took the timing cover off and there was oil up to the bush . So I put a small hole in the cavity about 20 mm up the side so that a little splashes about . The problem went away

Re: Oil laek from dynamo gasket

Posted: Tue Jun 25, 2019 2:46 pm
by alan.moore
Keith,
Is it possible that when it wet sumped, whilst standing for 6 weeks, the oil level reached the idler pinion bush and over time worked its way into the chain cavity?

Cheers
Alan