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74 GT750 Oil weeping from oil pump cover weep hole
Posted: Mon Sep 07, 2020 11:18 am
by Schase
I have a 1974 GT 750 I recently purchased that is weeping transmission oil from the weep hole in the cover of the oil pump. Also it fouls the left spark plug no matter the heat range installed I’ve tried NGK B6ES through B8ES. I’m starting to suspect the left crank case seal is faulty.
Any advice?
thanks
Re: 74 GT750 Oil weeping from oil pump cover weep hole
Posted: Mon Sep 07, 2020 12:53 pm
by karl pa
Welcome
The transmission vent is behind the oil pump, if it is weeping out the cover it could be pushing out the vent.
What is the oil level in the transmission? If it is over filled it can push out vent, or bad crank seals can do it.
Bad crank seals allow transmission oil to be pulled into cylinders and burnt, when this happens the transmission oil level drops.
What condition is the ignition system? could it be other reason for fouling plugs? points,condenser,carbs?
If it is crank seals, oil foiling the plugs I am afraid a rebuild.
Re: 74 GT750 Oil weeping from oil pump cover weep hole
Posted: Mon Sep 07, 2020 4:29 pm
by Schase
Carbs are rebuilt and synced, points are good, oil level correct, I suspect you are correct on the rebuild!
Re: 74 GT750 Oil weeping from oil pump cover weep hole
Posted: Mon Sep 07, 2020 5:54 pm
by jabcb
How does it run before fouling the plug?
You might have other ignition problems causing the left cylinder fouling. Some years ago I had serious oil accumulation due to a faulty plug cap.
Re: 74 GT750 Oil weeping from oil pump cover weep hole
Posted: Mon Sep 07, 2020 7:07 pm
by karl pa
Schase wrote:oil level correct,
If it is pulling enough oil in to foul the plugs, the transmission oil level will drop rather quickly.
I had bikes that dropped transmission oil in 400-500 miles but didn't foul plugs.
Pushing oil out vent is not a good sign, if not overfilled, pressure is coming from somewhere. how long does it run till it fouls plugs?
Re: 74 GT750 Oil weeping from oil pump cover weep hole
Posted: Fri Sep 11, 2020 2:55 am
by Schase
It fouls the left cylinder in a mile or two, tried B6ES through B8
Re: 74 GT750 Oil weeping from oil pump cover weep hole
Posted: Fri Sep 11, 2020 5:45 am
by karl pa
You can do a leak down test to check crank seals, I never did this test, but I believe you block intake and exhaust and put 5 psi of air in cylinder to check how long it holds. If it is oil fouling plugs in a mile or two, I think it should fall instantly.
Is the left plug oil soaked?
You can remove the SRIS check valves from the bottom of the crankcase and see if oil is puddled in cylinder, causing you plug fouling.