Oil coming out of the center cylinder on my GT750.

[Rassie]

I was taking out the water pump on my GT750 yesterday and turned the motor upside down to do it. I also took out the plugs so I could turn over the motor to check pump operation. In any case after I had been working for a while I noticed a small pool of oil about 3" in diameter that seems to have come out of the center cylinder on the intake side. The motor is slanted so that the intakes are lower. I had also before noticed that there was oil coming out of the center exhaust pipe where the header pipe goes into the head and assumed it was just a bad exhaust gasket. But now this pool of oil has be worried a bit. I suspect it can either be too much oil coming in from the oil pump or I have bad crank seals around my center cylinder. Any other ideas on a possible cause or regarding my own prognosis?

[Coyote]

The oil pump is not capable of feeding more to a particular cylinder. The same amount goes to all three. My guess is you have a bad check valve on the center oil line. If the valve is stuck open, it allows oil to gravity feed to the motor. This oil pools in the crankcase. When you inverted the motor, this oil would come out slowly because it has to find its way through 2 ring gaps.
I doubt this has anything to do with your crank seals. Is the oil relatively clean or is it black and burned?

[Rassie]

The oil looked very clean..as in the attached picture.



Also it seems the oil came out of all 3 cylinders, see the oil sitting on to top side of the inlet mouths. So I expect it is from just sitting.

[tz375]

If that's all that came out of all 3, that's normal. When the motor stands for a while, any oil in the crank drains down into the cases. All two strokes leave a remarkable amount of oil in the bottom end - even those running pre-mix.

It's worth checking the check valves while the motor is out and accessible.

[Rassie]

If that's all that came out of all 3, that's normal. When the motor stands for a while, any oil in the crank drains down into the cases. All two strokes leave a remarkable amount of oil in the bottom end - even those running pre-mix.

It's worth checking the check valves while the motor is out and accessible.

I think so as well. After taking another look at the oil lines I noticed there is some air in there I expect some drained in after I disconnected it. While I have the motor out I will check all the valves as you suggest.

BTW the bike was running very nicely when I started with the project. Had an oil leak somewhere and did get hot to the point where the gauge would go all the way up to the red but it was running nice and fired right up every time. Have not found any problems with the cooling system yet but just took out the water pump to replace it. I also flushed out the old coolant and then put some Evaporust in there and let it sit for 2 days, a whole bunch of stuff cam out. So I hope it is clean now. As a precaution that the overheating may have been due to a timing issue I also bought an electronic ignition kit for it. So hopefully I will have all the bases covered.