I could just be imagining things but it seems like if I fill the oil reservoir on my mc28 and it sits for any length of time that it is almost empty next time I'm going to ride it. It blows some oil out of the aftermarket pipes at the head but it doesn't seem like its that much.

Anywhere else it could go that it shouldn't? Also noticed the overflow bottle having a decent amount of oil looking liquid in it. 2 hoses in it, one from the rad I think and the other goes into the carb area in front of the vertical cylinder. However, no big oil stains anywhere or anything . . . hmmmm.
Thanks!

Hi Have you checked the engine oil ? As I think if the seal goes in the pump the 2 stroke oil can drain in to the gearbox.

Gearbox oil does need to be changed so will check that thanks. Does anyone know if a leaking pump seal can be bad enough to cause this much injector oil to drain into the crankcase just by gravity with the bike at rest? If this is the problem how much of a PITA is it to replace this seal?

I'll check the crankcase tonight and see what i find and maybe hit you guys up again for advice. Thanks!

It will all be in your gearbox
I suspect you'll find the oil pump seal has come adrift. Easy fix, clean it up and pop it back in with some goo.

Checked it out and thats exactly what it seems is happening, thanks guys. I assume then i need to remove the injector pump next to the vertical cylinder on the throttle side and inspect/replace the gasket or whatever seals it to the cases? Thanks again . . . was wondering where all that expensive oil was going!

It's only a rubber O-ring, so unlikely to need replacing. The oil seal itself isn't a part that can be bought from Honda (and it's an odd size, so difficult to obtain) but it rarely needs replacing. As Jeff says, clean it up and then carefully press it back into place with a little smear of instant gasket just to help bond it into place.
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Andy.
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is it a normal oring thats had the sides flattened?
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Honda nc23 CBR400 AERO 1986, 1990 honda NC23 Tri-Arm, 1987VFR400 NC24 Rothmans Rep, NSR250 MC16 1987, CL250s 1983. Moto guzzi zigolo 110cc 1958. Fantic 50cc 1972. Suzuki Cobra Race bike 500cc 2t 1975 , GP125 1975. Triumph T110 1954. BSA Thunderbird 1955. Ariel VB 600 1952, 1990 MuZ 125 etz.

I think you will find it's just a normal O-ring... 20 years of compression probably flattened the sides!!
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Andy.
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