Engine noise @ 3000 rpm like loose exhaust shield

Hubbbcappp · Apr 24, 2017

I have noticed my '91 ST 1100 has developed a worrying rattle at around 3,000 rpm. It sounds just like one of exhaust heat shields has come slightly loose (which is not the case) and seems to coming from the front of the engine. I have eliminated anything to do with the exhaust. It's not mph related, and so far I have failed to find anything loose externally.
Thing is I'm planning a long trip to France and Spain in 3 weeks time so am very keen to resolve the issue before then.
I would really welcome any thoughts on where to start looking.
Many thanks in anticipation...

Slydynbye · Apr 24, 2017

There is a a screw which holds small bracket inside the heat shield, if some clearance has developed it will rattle.
You won't see anything externally but, if you loosen the screw the little bracket will probably fall out. I have removed mine.

Upt' North · Apr 24, 2017

+ 2 Heathy and Slydynbye.
I had a similar rattle, although strangely it didn't worry me too much.
Couldn't track it down until it started to rattle on tickover.
It was the front left shield, it was all tight but needed a slight tweak to shut it up. I put it down to stress in the shield over time. It's been OK since.
Although I've described it as a rattle it was more of a resonance.
Hope it helps and it's that simple.
Upt'North.

Hubbbcappp · Apr 24, 2017

jfheath said:
Excuse the question - but what did you do to establish that it wasn't the shield ? I have had one of the bolts shear once, and the shield looked to be intact and secure. But then at a particular rev band (3000 sounds familiar) it would rattle like mad.
'Twanging' the shield between each of the 5 mount points should reveal any problem.
Other sources - there is a nice channel between the two downpipes on each side of the engine. It is a favourite hidey hole for any nut or bolt that went missing at the last service.
Also - the bolts that hold the exhaust at the manifold can work loose - and the clamp can rattle.

I'm not ignoring the comment that you have eliminated anything to do with the exhaust. Just speaking from my own experience after I once eliminated everything to do with the exhaust !!

Other possibles - the plastic radiator grill can produce odd rattle noises at certain revs - but that sounds more like a new tyre on wet tarmac than a tinny rattle.

Others have suggested the cam belt pullies behind the front engine cover. Stethoscope / screwdriver to the ear should help identify that one.

The anti-dive plunger at the bottom of one of the forks (I think it changes side between ABS and non ABS models) can result in a metallic rattle. The hole becomes very elongated.

Final suggestions - bad routing of the speedo cable. Spare keys / loose change in the fairing pocket.

Thanks for these suggestions. I took off all the fairings around the engine, tried all the heatshield bolts and then applied pressure to each heatshield whilst revving to 3000 rpm. Made no difference. Sounds like it's coming from engine. Definitely not the forks. I'll check the channel in the exhausts though!

Upt' North · Apr 25, 2017

Good luck HubbbCappp, if it's definitely RPM related then it's got to be about the engine although that could be that at 3000 RPM something else is resonating.
Let's hope it's the channel issue as described, if not you're going deeper.
Upt'North.

Engine noise @ 3000 rpm like loose exhaust shield

Hubbbcappp

Slydynbye

Will ride for Pie

Upt' North

Hubbbcappp

Upt' North