High Pitched Mystery Sound

[davem222]

Hey guys,
So the bike is finally up and running and I'm noticing something strange, or at least, I suppose is strange. I may be making a mountain out of a mole hill, but when I rev the engine under load I hear a kind of high pitched whir. It's not that loud but it's noticeable (to me anyway). The odd thing is that it's ONLY when the bike is under load. When I'm in neutral and rev the engine there's no high pitched sound. This makes me think it's something in the clutch or who knows. Anyone have any thoughts? I was going to video it and post but a) I don't know if the sound will show up on a recording as it's fairly faint compared to the sound of the engine in general and b) It's only under load so I'd have to record while riding, which would probably end up with me dead.
I'm not having any performance problems that I can notice, no stumbling, no stalling, she runs like a top. Let me know if anyone has any thoughts. Thanks.

Dave

 

[rebel542]

Have you changed anything?

 

[davem222]

I rebuilt the entire engine, so, yes I redid everything but did not replace the cam-chain or the cam chain guide. In retrospect I wish I had but the guide seemed almost new to me and the chain as well. I am still trying to work out the cam chain tension and the tappet clearance settings as I get some small clicking at high rpm (although again, this may be me just being over sensitive as the sound is slight). The reason I don't think it's the chain or the tappets is because when I'm in neutral and rev the engine the sound is completely gone. It is ONLY when the thing is under load, which is why I'm confused.

Dave

 

[Scrambled]

I have a steathascope (spell check ?) , like a doctor's but it has a thin mettle probe instead of the disc on the end . I got it at an auto supply years ago and it is the best thing there is for tracking down sounds coming from an engine. You just put the needle probe on the motor and move it to where the sound is the loudest . Best tool I ever bought.

 

[davem222]

Thats a great idea. Of course the fact that it only comes up under load is a problem. How can I put the stethascope on it while riding lol.

 

[Scrambled]

Thats a great idea. Of course the fact that it only comes up under load is a problem. How can I put the stethascope on it while riding lol.

You may be able ,with some help, to put it on the center stand or a bike stand , and have the bike running in gear . Use the throttle and brakes to give it a load . Just an idea .

 

[peanut]

have you tried cutting the engine whilst riding and coasting ?
Might eliminate the engine if you can still hear the noise .

 

[nj1639]

Good idea Peanut.

I'm having an issue with the '83 but reversed....noise dissappears under load or braking. Thinking front wheel bearing.

 

[littlebill31]

My one bike made a similar sound and it was the cam chain. It was very faint, but you could hear a "tinging". Drove me nuts once I started hearing it. There was no problem, it just made that noise.
I'm surprised most can hear anything over the tappets, lol.

 

[Scrambled]

No takers for all the stuff you offered to trade littlebill ? Looks like a good deal for someone. ( I am in Canada , so I can't)

 

[davem222]

Heya Peanut, yes, good call, I haven't tried killing the engine entirely, but when I give it zero throttle when I coast the noise goes away. So I do think it's some sound coming from the engine/transmission. The noise only comes back when I give it throttle under load and the noise is proportional to the throttle I give it, low throttle, low pitched noise, higher throttle, higher pitched noise.

 

[XSLeo]

Might be the drive chain. If too loose or to tight they make noise.
Leo

 

[davem222]

Gotcha. Maybe I'll lube it up real good and reset the tension. Although wouldn't it still make the noise then even if Im not giving throttle when Im riding as the rear wheel is still spinning.

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[XSLeo]

The drive chain wears in a fashion that gets more wear on the drive side of the sprockets and rollers. The noise may only occur when pressure is applied to the drive line as when under load. Coasting removes this pressure.
Does it make the noise in all gears?
Leo

 

[davem222]

Oh, yeah, that makes a lot of sense. Yes, coasting removes the noise completely.

Dave

 

[davem222]

Sorry, didn't answer your question. Yup, all gears.

 

[Tomterrific]

Two things I can think of and each is dangerous.

1. Detonation. Fill the tank with 93 octane premium or the highest you can get. Does the sound go away?

2. The head gasket may be leaking a bit and making a peep or short sharp tick under load. This could also be an exhaust gasket/head pipe.

I would not describe these as a whir but more of a tick or high pitched jingle.

Same noise cold or hot? ...low or higher revs?

Tom

 

[davem222]

Yup, same noise cold and hot, low revs and high, although the pitch changes to higher as the revs go up. Detonation? Hmm, the bike doesn't skip a beat though, the engine (other than the sound obviously) runs really well. How is the head gasket leaking a bit something that's dangerous?

 

[davem222]

Also I am and have been using premium if that means anything re: detonation.
Dave

 

[davem222]

Just listened to detonation vids online and my sound is nothing like the "marbles rattling around" sound that seems to be detonation. Mine is more like the high pitched sound of an RC car revving up.

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