Topic: CB500K3 Transmission main shaft "plug" seal

[vaiski]

I have had a minor oil leak from the left side of the engine since I bought the bike last summer. I replaced all the shifter shaft and oil pump seals during the wintertime, but that did not fix the problem. The previous owner damaged the engine case with o-ring chain and I am afraid the oil leak is caused by the chewed-up plug seal (91207374000). I have ordered the replacement and I'm planning the replace it soon as I receive the new seal.

Can someone verify, that the seal is replaceable without splitting the cases.. If not, is there any other ways to approach this leaking seal problem..

Im going to run a standard 530 chain and 3mm spacer under the machined front sprocket. I found that even with a standard chain the clearance between the chain and case is very tight..

[bryanj]

To fit properly its a case split job as its a very tight fit.
Have you checked to oil pump cover, the O ring in there can, and does, leak its 46x2mm

[vaiski]

Okay, that's bad news.. The oil pump cover o ring indeed is the one that has not been replaced since it is not available as a spare part. I will tackle that out of the equation with a general o ring from the hardware store.

Is the plug seal likely to leak because of the wear from the chain rub? There is no visible puncture and the rubber coating around the plug seems also solid. 

[bryanj]

There is a Goldwing seal at 46x2 if it is easier for you to get Honda parts

[Little_Phil]

It's 91305-426-003, but I'm sure you can get cheaper.

[bryanj]

You probably can but sometimes a Honda dealer is closer and easier.
If you find Nurse Julie on here she will sell you an oil pump O ring kit including the cover one but she is in uk like me, i used to do them but my supplier changed his minimum order amount to a reiculously high number!

[craz1]

The original seal had a lip that sat in the a groove in the case I believe. The replacement did not so it may be possible to pry it out and press the new one in but yes it is a tight fit.

[dave500]

the crankshaft main seals have the lip,that case one is just straight no lip,ive replaced them in situ easy enough,your might be ok,the oil may be from as mentioned the oil pump,or the sender unit,ive seen those seals really rubbed and not leaking.

[RAFster122s]

Sender bodies can develop leaks and oil can travel through capillary action and thin films, both can drive you to drink on tracing them. Clean things up and a bit of spray on foot powder can show you where the oil is coming from. Messy but effective way to trace and find the leak and not too bad a clean up issue afterwards.

[vaiski]

Thanks for the tips!

Little update for the case. The oil leak was traced in to the plug seal. Bike on center stand and after couple minutes of idling the oil started to dribble on the seal where rubber coating was chewed away. After some internet I found that some are successfully patched the leaking seal with JBweld kind epoxy product. Patched the seal where the aluminum was visible and finished it with good old engine silicone.

So far no leaks.. let see how long it will hold. The replacement seal is ready to go if the problem comes back. As previously mentioned the replacement seal looks that it could be pressed in without any case splitting. Hopefully I dont need to test that.

To prevent any future problems the front sprocket did receive some machining. 2mm off and 3mm spacer between the drive shaft and sprocket. Some photos attached.