'81 Honda making a whine??

[Mrs. DantesDame]

Forgive me for my limited information with this question, but the bike belongs to my nephew and it's difficult to get all of the facts that might be helpful  

Here's what I know: he just bought an '81 Honda CB750. It is apparently very clean and it runs great. I'd guess he's had it about a month or two. I don't know anything else about the bike (mileage, maintenance records, etc). Matthew (nephew in question) says that when the motor's at 4K he hears a "whine". It goes away as soon as he goes above/below 4K and there is no change in performance. He can't pinpoint where the noise is coming from other than "the engine".


So - any thoughts in what might cause this?    We're both curious now, as I've never heard of a bike doing this.

[county]

The Japanese are/were known for allowing their motorcycles to make whatever mechanical noise the bike might produce.  They made no effort to produce a distinctive sound like Harley.

I have no idea what the noise is.

[chornbe]

It's gear harmonics. Nothing to worry about.

[Mrs. DantesDame]

It's gear harmonics. Nothing to worry about.

That's what I was guessing at, but since I'd never even heard of it, I wasn't too sure. However, knowing what you know, I'll take your word for it :-)

[maddjack]

DD I had a 78, it did the same exact thing. No worries

[Mrs. DantesDame]

I had a '74, but was so clueless about bikes I probably never even noticed it  

[Andrew]

It's a honda, isin't it suppose to sound like a sowing machine  


(gear noise, mighty common)

[Mrs. DantesDame]

It's a honda, isin't it suppose to sound like a sowing machine  


(gear noise, mighty common)

No, no - you've got it wrong. The KLR is the sowing machine (ie, tractor). The BMW is the sewing machine  

[Andrew]

OK so one puts a ribbon down, one plants seeds, and one is just an old honda

I got it now

[BillL]

Knowledgeable community here

http://www.cb1100f.net/

[JonS]

Knowledgeable community here

http://www.cb1100f.net/

I owned a 1981 CB900F, which is almost identical, except for the displacement. My guess would be that the cam chains need to be tightened. It is a simple procedure.  Those bikes are pretty bullet proof and whatever it might be its probably no big deal.
 I was a member of that forum and there are a bunch of knowledgeable guys there.