Oil leak at crankshaft behind starter clutch

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Oil leak at crankshaft behind starter clutch

09 Jul 2026 16:09 - Yesterday 17:02
#925631
Can this seal be replaced without splitting the engine open? Hoping I can just pull off the starter clutch (maybe called a dynamo?)and gear and replace the seal. 1975 kz400
1975 KZ400
Last edit: Yesterday 17:02 by spyshot.

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Re: Oil leak at crankshaft behind starter clutch

09 Jul 2026 16:57
#925632
I dont know what bike you are referring to, but im going to assure youre talking about a 1975 kz400 based on your previous posts. Im pretty sure that there is supposed to be a bit of oil behind the alternator cover to lubricate the starter clutch. Are you sure that the seal is leaking? 
1982 KZ1000M2 CSR - damaged
1983 KZ440D5 LTD
1985 GPz 550A2

Craig

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Re: Oil leak at crankshaft behind starter clutch

Yesterday 17:03
#925633
This area is supposed to be dry. No oil passage or return. 
1975 kz400
1975 KZ400

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Re: Oil leak at crankshaft behind starter clutch

Yesterday 21:32
#925635
This area is supposed to be dry. No oil passage or return. 
1975 kz400

 
This has been brought up on the forum previously here .

Here is an oil routing diagram. See how an arrow points into the left cover area.  
I just dont want you wasting your money and time.
1982 KZ1000M2 CSR - damaged
1983 KZ440D5 LTD
1985 GPz 550A2

Craig

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Re: Oil leak at crankshaft behind starter clutch

Yesterday 16:09 - Yesterday 16:15
#925657
Yes, I’ve seen that diagram. It is very hard to see, but I think it’s pointing to the end of the crankshaft inside the crank case. Again, there are no oil passages inside the stater cover and no returns.

I have also read the thread on this, and I disagree with their conclusion. In addition to this, there is a mechanic on YouTube that completely rebuilt one of these engines and also states that this area is supposed to be dry. I ran the engine with the cover off and got no oil at all.

there is an oil seal behind the dynamo/generator. I believe this is leaking on mine and I am in the process of ordering a new one to get it replaced. Must only be leaking when it’s under load or when it gets hot.

thanks for checking up on me though
1975 KZ400
Last edit: Yesterday 16:15 by spyshot.
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Re: Oil leak at crankshaft behind starter clutch

Today 17:21
#925658
If you will be replacing the seal then it would be ideal to have an alternator rotor puller tool handy, which if you have watched an engine disassembly, you may already know this. Other than pulling the rotor, getting to the seal is not terribly difficult.

You may attempt to remove the seal without splitting the cases but be very careful to not damage any metal surfaces because then it definitely won't seal. If you cannot remove the seal without splitting the cases, then the seal is probably too damaged and will definitely require the cases to be split.

Be ready for replacing many gaskets, o-rings, and having to assemble the whole engine without damaging anything, such as piston rings, or valves from incorrectly set timing. If you are ready for this though, it would be a great learning experience if you haven't done something like this before.

By the way, care if you share a pic of your bike? I've always wanted one in the old style, but im stuck with my 440.... I guess its good enough 
1982 KZ1000M2 CSR - damaged
1983 KZ440D5 LTD
1985 GPz 550A2

Craig

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