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Hello,

I just bought a 1983 Nighthawk last week. It runs great! Only problem is, I've noticed a little bit of oil leaking. I'm new to the bike, and never done much work on any of my own bikes in the past, so I can't tell you what part this is leaking from. But below is a link to an album, in which I circled the bolt or plug on the rear of the motorcycle that the oil is slowly coming out of. It is getting onto the back tire when I ride, which is obviously not good at all.

I tried tightening the circled bolt/plug, but when I start, it was already a little loose, and instead of tightening, it just spins around and around.

Any suggestions would help -- I would really appreciate it!
 

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That's your final drive fluid. That gray thing is the fill port plug and it has an o-ring beneath it which likely needs to be replaced. Not a big deal at all, though sometimes the plugs can be a bit of a pain to remove if they've been on for a while.

Might just be loose too.
 

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If it just keeps spinning around something is likely stripped. Probably should remove the plug and find out whether it's the plug or the housing. The plug is obviously easy to replace.

Make sure a drain pan is under it.
 

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Make sure you have gear oil to go back in. Your Honda dealer can tell you what is recommended.

If it just spins when you try to take it out try a set of vise grips and pull out as you turn.

I'm sure that can also order you a replacement plug, but it might take a few days to come in.

Don't let that final drive run dry or you won't have one...
 

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Don't forget to replace the crush washer under the bolt too, probably why its stripped. Most likely it leaked under the previous owner and instead of replacing the crush washer, he over torqued the bolt.
 

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It's actually a rubber o-ring under that cap and for some reason when corrosion sets in they sometimes become absolutely immovable. Not sure if this is related to it being stripped - the OP will have to pull it apart and see what's going on.
 

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It's actually a rubber o-ring under that cap and for some reason when corrosion sets in they sometimes become absolutely immovable. Not sure if this is related to it being stripped - the OP will have to pull it apart and see what's going on.
That's interesting, I've never seen an O ring used in that application on bikes final drive, if overtightened, no wonder it leaked. I've had three different bikes with shaft drive, two Triumphs and currently a Moto Guzzi, all use a crush washer (just like on the oil drain ports) on the final drive gear oil port, none never leaked. Do they still use O rings on the fill or drain port on current models?
 

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Sounds like it's stripped, you'll probably end up having to retap it to a larger size and get a bigger plug or use an insert to restore the threads. If your a mechanic you've done this kind of work before you'll know exactly what I mean, if not then you might want to get it to a small local shop that fixes old bikes ( or cars), it's not a big deal to fix and they do stuff like this every day but it can be a bit delicate and you don't want to screw up that final drive.
 
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