Leaking Oil

[Syd]

I have a 1975 GT750M. I just had the tank and side covers repainted Gypsy Candy Red, rechromed the pipes and fitted reconditioned gauges. I had also replaced the clutch, filled the bike with new transmission oil and drained and flushed the cooling system and refilled etc. After a test ride over the weekend, I noticed some small drops of leaking oil coming from under the centre of the bike and the oil looks to be contaminated with green anti freeze from the cooling system. I assume this could be from the water pump seal? Any ideas on where to go from here?

[H2RICK]

I assume this could be from the water pump seal? Any ideas on where to go from here?

Pretty safe assumption, IMO.
What did you put in the transmission for lubricant ?? Some synthetic oils MAY cause problems with seals on these old bikes, especially the lighter weight synthetics. If you've used a lightweight multigrade engine oil OR a lightweight (e.g. SAE70W) gear oil you MAY want to consider trying an 85W or even 90W dino gear oil. This MAY solve your problem if you've got a synthetic in there now.
Otherwise......you're in for an overhaul of your water pump sealing system.....a nice winter project.

[Syd]

Good point..

I used Valvoline HP GL-5 rated Gear Oil 80W/90 which is not synthetic. On closer inspection, I found that the water pump cover gasket was weeping and tightened up the cover bolts. Maybe the cooling fluid leaked at this point mixed with some residual surface engine oil under the bike. Checked the engine oil and cannot see any signs of cooling fluid. Will keep an eye on things..

[MikeH1A]

Syd, Just carry a rag to wipe the engine with and then line the garage with a suitable covering to absorp stray leaks - much less stressful

When are you going to bring her out on a ride????? The boys are keen to see your handy work.

[H2RICK]

Checked the engine oil and cannot see any signs of cooling fluid. Will keep an eye on things..

Hopefully you've solved the problem but, yes, do keep an eye on things. Antifreeze makes a VERY poor transmission lubricant.

PS: You made a good choice for transmission lube. GL5 is what you want to see on the bottle.
80W90 might be a little stiff on a cool morning.....but if you're down under, then you're just getting into the hotter weather, I'm guessing, so you should be okay. Let your shifter toe tell you if the 80W90 is too viscous.....or just right.