Rear engine oil leak

Side valve, 803, 948, 1098., 1275 and Vizard mods

Rear engine oil leak

Postby Corn22 » Sat Sep 17, 2016 6:44 pm

I seem to have an engine oil leak that is putting oil into the gearbox bell housing so it gets in the clutch and comes out of the bottom where the split pin is. I have checked the gearbox and that's not loosing oil but the engine is. Where is the most likely place it us coming from? I will taking the engine out at some point but just need to know where to start. Thanks
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Re: Rear engine oil leak

Postby Panky » Sat Sep 17, 2016 8:16 pm

Make sure the breather system is working OK and not blocked, if the crank case is pressurising it will force oil through the scroll on the rear of the crankshaft and into the bell housing.
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Re: Rear engine oil leak

Postby Corn22 » Sat Sep 17, 2016 9:13 pm

Thanks will check that
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Re: Rear engine oil leak

Postby emjay » Tue Sep 20, 2016 5:05 pm

Make note of the oil pump cavity. 948 and older had the can soldered in place and can crack.
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Re: Rear engine oil leak

Postby Corn22 » Tue Sep 20, 2016 5:38 pm

It's a 1098, still need to check the breather on the engine. The one on the rocker cover is clear
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Re: Rear engine oil leak

Postby Corn22 » Tue Sep 27, 2016 9:30 am

Well I have checked both breathers and they are all clear. It looks like the rear block cover maybe leaking some oil, could it get from there not the bell housing? I don't see how but I am not an expert. Not sure what else to check unless its just a worth engine?
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Re: Rear engine oil leak

Postby Panky » Tue Sep 27, 2016 10:06 am

When the engine is warm take the oil filler cap off and rev the engine, can you feel a significant blow, or see fumes, coming out of the filler. If you can it could be worn valve guides or rings. Is the vent piped to the vac connection on the carb and if not is there a blanked off brass stub on the side of the carb?
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Re: Rear engine oil leak

Postby Corn22 » Tue Sep 27, 2016 10:17 am

Thanks Will check that when it stops raining. The rocker cover vent goes to the air filter, is it better to go to the carb?
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Re: Rear engine oil leak

Postby Panky » Tue Sep 27, 2016 10:19 am

Yes definitely. The port on the side draws more of a vacuum and all later engines had the breather connected there, you don't get oily sludge all over the filter either ;)
Once it's connected direct to the carb you might need to make the mixture slightly richer as you will be drawing in a bit more air.
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Re: Rear engine oil leak

Postby Corn22 » Tue Sep 27, 2016 10:20 am

Panky wrote:Yes definitely. The port on the side draws more of a vacuum and all later engines had the breather connected there, you don't get oily sludge all over the filter either ;)

Cool will change it, just need to get the rain to piss off now :roll:
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Re: Rear engine oil leak

Postby Corn22 » Wed Sep 28, 2016 7:18 am

Well I have moved the breather pipe to the carb, had to modifier the pipe as the carb connection is smaller. For some reason in increased the tick over which I had to adjust down? Check for fumes and blowing from the filler but none of either. Is it possible the engine is just a bit worn out?
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Re: Rear engine oil leak

Postby Panky » Wed Sep 28, 2016 8:37 am

It could be wear in the rear crankshaft bearing, there isn't any seal on the crankshaft just a scroll that 'screws' the oil back into the sump so if there is any slight wear it can lead to a leak as you described. Give the new breather a chance though as it will take a while for any oil that has already leaked to clear up.
Is the oil definitely coming out of the jiggle pin in the bottom of the bell housing? If it's leaking down the front of the engine plate then it could be coming from the cork seal on the bearing cap.
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Re: Rear engine oil leak

Postby Corn22 » Wed Sep 28, 2016 8:39 am

Thanks for your help I will see how it goes. I am sure it is coming out of the jiggle pin
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