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woodly1069 01-06-2013 05:01 PM

Rear main leak...or ???
Ok fellas I have pulled my old R75/5 all apart for more reasons than just one but this is on the list to repair. I have had a small leak and assumed it was the rear main. After pulling things apart I really dont know if the main was leaking at alll. I will replace it but it looks to me as if this lower plate may be the actual culprit, what do you think?
I know it's hard to see but the main seal looks in tact. Could it be the lower plate seal also?

JonnyCash 01-06-2013 05:34 PM

From your pictures, I would say you're right, it's the oil pump cover. There's an o-ring under that cover. If it were the rear main, I'd expect to see oil thrown all around, not just down.

disston 01-06-2013 05:54 PM

It looks like that is the original rear main seal. Make sure you change it. It has served well but it's time to go has come.

The oil pump cover O-rings do go bad and leak.

Brun 01-06-2013 06:10 PM

And do replace the transmission input shaft seal as well.

woodly1069 01-06-2013 06:28 PM

Will do, just as I expected! THANKS GUYS!

jackd 01-06-2013 07:15 PM

Maybe someone has changed the rear main seal in the intervening time since the bike was built - it seems to be dry as a bone and who knows what age it is? Personally I wouldn't go farther than changing the oil pump cover seal - that seems to be a logical thing to do. But then I don't like finding more work than I have to. Your call.

Kai Ju 01-06-2013 07:16 PM

Did you block the crank ? Please say yes.....

woodly1069 01-06-2013 07:36 PM

I think I will change the rear main as well as the oil pump plate seal; hopefully that will do the trick. As far as blocking the crank I am unfortunately in the dark, what do you mean?...please advise.

ozmoses 01-06-2013 07:41 PM


If your crank rotates it may shift forward coming off the thrust bearing.

ignatz72 01-06-2013 07:41 PM

Oh boy...

woodly1069 01-06-2013 07:45 PM

OK call me stupid, I'm sure the thing rotated at least 90 degrees but I marked it and put it back where it was when I started. How does it come off the thrust bearing? I don't understand...isn't the thrust incorporated into the mains?

ozmoses 01-06-2013 07:56 PM

You're not stupid. Read the link I provided, all the info is there.

woodly1069 01-06-2013 07:58 PM

OK thanks

jackd 01-06-2013 08:16 PM

All is not lost. Pull the front cover off the engine (by the alternator) and see where your alternator brushes presently are running on the rotor slip ring. If the crank has slipped ahead the carbon brushes will be contacting to the rear of where they usually locate. If they are still running in the same spot as usual then the crank hasn't moved and the thrust bearings have not come off their perches. If that's the case, then now is the time to block the crank at the front of said alternator.

If your level of experience is limited with these machines then maybe you should take a pass on doing the rear seal and stick to the oil pump cover.

ME 109 01-06-2013 08:21 PM

Some good detective work there jackd.
Those dowels/pins that retain the thrust washer are about three mm long from memory.

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