Oil leak at gear train cover?

[Jessezm]

Got my bike (1972 xs2) running smoothly after a total restoration. It's got 7,600 miles and a fresh top-end, but didn't touch the bottom end. Since everything on the motor is freshly vapor blasted and the bottom end is painted new in duplicolor aluminum, it's pretty easy to detect leaks.

Thankfully the top end is leak free (retorqued after the first few heat cycles for good measure), but there is a drip on the bottom end left side, and seems to be emanating from the bolts that hold the gear train cover on. There is a wee bit of oil on a top bolt or two, and then it is visible on the bottom bolts. it seems to be coming from under the bolts rather than at the gasket surface if that makes sense? I guess it would as the gasket would presumably start to give from the inside out, and reach the bolt holes first?

Or is this possibly an optical illusion and the leak is actually coming from the more notorious clutch pushrod seal or drive gear? Thing is, I've shined a bright light up in there and see no evidence of oil dripping down onto the gear train cover.

Just want to put the question out there - is it worth trying to install copper crush washers and under the bolts to stop the leak or is it a definite gasket replacement? I have read the threads cautioning about over-torquing those bolts, so I'll be careful...

The leak is pretty minor but on a brand new restoration, it's pretty annoying! Plus I park the thing in my dining room so there's that...

 

[xjwmx]

Just want to put the question out there - is it worth trying to install copper crush washers and under the bolts to stop the leak or is it a definite gasket replacement? I have read the threads cautioning about over-torquing those bolts, so I'll be careful...

It should work like it came from the factory without copper washers there. Gasket should stop the oil before it ever gets to the bolt. If you think it's the gasket, I made one for it from that dark gray gasket paper from Advance. Not hard. Just tape a piece of it to the cover and go around it with a sharp knife.

Possible the oil is coming from the sump cover (can make the same kind of gasket for it) or from one of the seals - pushrod, countershaft, shifter. Or could be oil flung off your chain if it's not real bad.

 

[Jessezm]

Looks like fresh oil from the motor, not the chain. And not the sump cover--that has a new gasket and is dry. I've got a full engine gasket set so I should have the right gasket for the gear train, just wanting to avoid draining the fresh oil. I guess since it's a fresh top-end, I may as well do an oil change soon anyways. Plus I may have to mess with the clutch anyways... It's sticking (saving that one for another post...)

 

[xjwmx]

And not the sump cover--that has a new gasket and is dry.

I must have misread you. Most likely culprit that side is loose drive gear letting oil past it, or possibly bad countershaft seal. With the drive gear off you can see if oil is welling on the seal. Drive gear nut calls for 47 ft lbs. Bad pushrod seal would be obvious, shifter seal, least likely.

 

[gggGary]

Pull the cover, replace gasket, it's not that hard. I'd put a light smear of sealer 'tween cover and gasket, light smear of grease 'tween gasket and case. Had one leak a time or two.

 

[5twins]

I advise you go tighter than 47 pounds on that sprocket nut. That's one of the later specs and some of those were as little as 36 pounds. That's silly loose for a nut that big and especially one that's expected to seal several metal to metal surfaces. I use the spec from the earlier models which is about 90 pounds. The actual early spec is 10-13 m-kg (72-95 ft/lbs).

 

[xjwmx]

^I just go by the book (supplement for my year). It always works

 

[Jessezm]

Thanks, gents! I'll pull the cover on that side so I can look at all the possible culprits a bit closer, but hopefully will be as easy as gggGary says