St1100 engine noise when idling when hot

Hell everybody. Maybe somebody out there can help me. My st1100 has developed a loud whining sound coming from the engine when it's idling. Only when it's hot. Sounds perfectly normal when it's cold. When I put my ear to the engine, the sound seems to be loudest at the location of the camshafts on both sides. It's a really nasty loud whine.
When I rev the engine the noise stops. It's 1991 with 148000 miles on it. I replaced the timing belt, idler pully and tensioner last summer. It has done a few thousand miles since then without any bother. Any ideas? Thanks

Mine is the same; I replaced the timing belt (Gates T325 IIRC) and since then the whine at idle is much more noticeable, but disappears when moving. I have had the belt cover off to recheck the tension but all is fine and the belt looks happy. I put it down to a "characteristic" rather than a fault...

sosdingle said:

the sound seems to be loudest at the location of the camshafts on both sides.

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if you didn't change the water pump while you were in there, its possible its the water pump bearing making the noise. If you can prove the sound is from the camshafts and rule out the pump, then maybe yours and Terry's have similar symptoms.

Terry, did you change your water pump???

dwalby said:

if you didn't change the water pump while you were in there, its possible its the water pump bearing making the noise. If you can prove the sound is from the camshafts and rule out the pump, then maybe yours and Terry's have similar symptoms.

Terry, did you change your water pump???

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No I did not touch the pump.

jfheath said:

Stick a screwdriver handle against your ear and touch the blade end at various points on the engine. That will help determine whether it is camshaft or another location.
It is remarkable how effective this is for locating the source of noise.

Be sure to put a small dab of black grease on the end of the handle first. No reason, I just don't want to be the only one to have done that !!

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You can get a mechanics stethoscope with a long metal rod on it inexpensively. These make it much easier to find the source of the noise than the old screwdriver trick. But, per John, you can still put that dab of grease on the earpieces first....

Re: St1100 engine noise

How's your oil level? What kind of oil? Could the cam gears not be getting enough oil?

Re: St1100 engine noise

dkruitz said:

How's your oil level? What kind of oil? Could the cam gears not be getting enough oil?

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Oil level is fine. It's silkolene super 4. It's a good quality oil. I have now done some dismantling and the noise seems to be coming more from inside the cambelt cover. It's very difficult to pinpoint it. At first I thought it was the cam gears.When I get time I will remove the cambelt covers and inspect. Not getting enough oil is interesting. Could that be caused by a weakening oil pump. I guess this would be most apparent at tickover.

SMSW said:

You can get a mechanics stethoscope with a long metal rod on it inexpensively. These make it much easier to find the source of the noise than the old screwdriver trick. But, per John, you can still put that dab of grease on the earpieces first....

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I got a stethoscope today. It doesn't seem to be coming from the cam gears after all. I took off the inspection cover for the cambelt. The sound increased when I did this. It appeares to be coming from in there. I will check further when I get time. The sound is travelling a bit which makes it difficult to pinpoint. The only thing that wasn't changed in there last summer was the waterpump. It's working fine. No issues with cooling system. Could it make a sound of this type. That is , a loud whine at idle only, and only when hot? When I changed the cambelt I used a gates belt same as terry. To be honest, this doesn't sound like a cambelt noise. But I could be wrong.

Re: St1100 engine noise

It might be the Cam belt idler bearing which is under that cover.
If it hasn't been done it's probably time to change the belt and the idler.

sosdingle said:

Hell everybody. Maybe somebody out there can help me. My st1100 has developed a loud whining sound coming from the engine when it's idling. Only when it's hot. Sounds perfectly normal when it's cold. When I put my ear to the engine, the sound seems to be loudest at the location of the camshafts on both sides. It's a really nasty loud whine.
When I rev the engine the noise stops. It's 1991 with 148000 miles on it. I replaced the timing belt, idler pully and tensioner last summer. It has done a few thousand miles since then without any bother. Any ideas? Thanks

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My first suspicion, since wasn't mentioned, is idle needs to be at 11-1200rpm. Secondly, carbs need idle mixtures re-set along with a carb sync. First suspicion of needing idle mixtures re-adjusted and carb sync is when motor is warmed up to operating temp., the idle fluxuates up and down 50-100rpms..

The cambelt idler, tensioner and belt were done last Summer. They have only done a few thousand miles.

Thanks for that info Brant. The engine idles at 1100 revs. If it goes below this , can such a noise appear and be as loud as it is. Sometimes idle will drop when cooling fan comes on. What exactly would make the whining noise. The idle does fluctuate a bit . Is it difficult to reset idle mixtures?
Carb balancing I have done before , so this I can do.

With the inspection port removed can you tell if maybe the belt is frayed? I realize it shouldn't be with that few of miles.

dkruitz said:

With the inspection port removed can you tell if maybe the belt is frayed? I realize it shouldn't be with that few of miles.

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Hello. The belt looks perfect.

Re: St1100 engine noise

sosdingle said:

I have now done some dismantling and the noise seems to be coming more from inside the cambelt cover. It's very difficult to pinpoint it. At first I thought it was the cam gears.

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if you've ruled out the cam gears, and its coming from inside the front cover, its most likely your water pump bearing, since you claimed earlier that the other pulleys were replaced when the belt was done. When my water pump went it made a whining noise like you're describing.

Re: St1100 engine noise

dwalby said:

if you've ruled out the cam gears, and its coming from inside the front cover, its most likely your water pump bearing, since you claimed earlier that the other pulleys were replaced when the belt was done. When my water pump went it made a whining noise like you're describing.

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Thank you. Yes, you are probably right. The waterpump is the only part in there that has not been replaced. Did yours only whine while idling also? I guess the only way I will know for sure is to replace it.

Re: St1100 engine noise

sosdingle said:

Did yours only whine while idling also?

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Its been almost 4 years since I replaced it, so my memory is weak, but I think it did.

Funny thing about getting older is the threshold for what's important enough to remember gets so high that you forget things the minute they are no longer useful, anyone else notice that?

Re: St1100 engine noise

dwalby said:

Its been almost 4 years since I replaced it, so my memory is weak, but I think it did.

Funny thing about getting older is the threshold for what's important enough to remember gets so high that you forget things the minute they are no longer useful, anyone else notice that?

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I agree with you 100%. I will get the waterpump off as soon as I get time. When I do, I will give an update here. Thanks to everyone for your help.

If the belt tensioner is too tight it can make that noise. Loosen it then tighten it spring tension only. When the old dodge 2.2 engines came out If you didn't use the tension tool and thought the belt was tight enough they whined at idle. Loosen it up a bit and it was fine.

Al st1100 said:

If the belt tensioner is too tight it can make that noise. Loosen it then tighten it spring tension only. When the old dodge 2.2 engines came out If you didn't use the tension tool and thought the belt was tight enough they whined at idle. Loosen it up a bit and it was fine.

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N.B. - the ST1100 timing belt does not run under tension. Follow the final step in the Honda Service Manual carefully when locking that pulley/bearing down.

John