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Discussion Starter #1
Hi everyone,

I'm having some disturbing sounds coming out of my bike and it seems to be getting worse. There is a high speed/high frequency clacking and almost sometimes grindy metallic sound coming from my '81 CM400C that I recently got (this is my first Honda). It was fine for the first couple hundred miles, and now this. It sounds like its coming from low, and maybe almost behind me when I'm on it, but it could be coming from elsewhere and its playing tricks on my ears. I've checked all the fluids etc and some basics and all that stuff is okay. Here are some details:

-Mostly in lower gears (1st/2nd) when I'm accelerating
-Doesn't happen when I have my hand on the clutch and I roll it around
-Doesn't happen in neutral or when I'm on the clutch and I rev the engine
-The second I start letting out that clutch the noise begins
-Almost disappears if I'm in higher gears and going above about 20
-Super annoying, probably not good for bike lol

Any help or suggestions are much appreciated. Thanks.
 

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You did some good troubleshooting, which should help track it down. My guess is that it is in the final drive, or less probably in the transmission.

Check the chain for proper lubrication and cleanliness. Take a close look and make sure that each link is moving freely without any binding. Check to be sure the tension is in spec with the right amount of slack.

Next check the sprockets to make sure they are in line and are not worn. The teeth should be even-looking without any "hook" shape to them.

Check the rear wheel bearings for wear. Even a little wiggling will signify that they are in need of replacement.
 

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Discussion Starter #4
So I looked a little at the chain and sprockets. The chain looks like it could use serious lubrication. Almost looks dry and dusty red. No corrosion though. It doesn't get much play up and down, just in the range it describes in the user manual. The sprocket looks mostly okay, but it got dark as hell and my garage light sucks. I'll look more in the morning and check around more and try and get some chain lubricant. Thanks.
 

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Discussion Starter #5
Well look at that..... I think the guy I just bought it from didn't take care of the chain at all. I used some cleaner for it went over the whole thing with a brush and then went over it all again with a good chain lubricant and it runs like a top. Thanks everyone. If you're ever in Boston, I owe you a beer.
 
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