Hi All,

I'm getting my 1971 Cota 247 ready for the upcoming vintage season, and I've got an oil leak that is driving me crazy. Both the gearbox and clutch drain plugs just refuse to seal (the 2 large flat head screws on the very bottom of the engine). I've tried fiber washers, aluminum washers, and rubber o-rings, with no joy. The fiber and aluminum washers continued to leak, and the o-ring just pushed out from under the head of the screw. The leaks are slow, just a small puddle after a day or two, but with no way to check the level, I have to change the oil before each ride.

Any suggestions?

Edited June 1, 200719 yr by SherpaT

try a little smaller o-ring, and just finger tighten plus 1/4 turn. It won't undo itself.

I don't know too much about Montesas, but I think a dowty washer is what you need. It is a steel washer with a rubber lip seal bonded to the inside of it. The rubber stands slightly proud of the steel and gives a good seal even if the surface isn't completely smooth. They might be known as something else in the US, but if you go to a bearing & seal stockist, they should be able to help you. Also worth checking that any breather pipe or valve is good and clear in case the 'box is pressurising slightly.

Good luck and a Happy New Year,

Mike.

I'm having the same problem with the clutch drain plug on my Sherpas, just cannot get a seal. I replaced the fibre washer and covered it in red hermetite, that does the trick nicely. I know it is a little bit of a bodge but stops the big red puddle under the bike after a couple of days.

Drain the oil and clean the threads on both the oil plug and the crankcase. Once they are nice and clean with no oil residue on either (drain well and clean with a little gas or alcohol) put some loctite silicone gasket maker on both threads. Put some on the fiber washer as well. Tighten and it should be ok.

Thanks for all the ideas!

I took the drain plugs out this weekend, and measured them, and ordered a few dowty type washers from McMaster-Carr. If that doesn't work, I'll try the silicone gasket maker. I'll report back with the results.

Edited January 12, 200719 yr by SherpaT