ST1100 engine vibration

[PeterW3035]

Can anyone help with some advice to a total non-mechanically minded rider?

A few facts 2001 ST1100 bought privately through Ebay :
No service history other than a receipt for the last annual service.
Externally was in very good condition with only 8000 miles on the clock.

The owner had owned the bike for 7 years and through a period of illness had lost confidence in the bike so had only put a few hundred miles on it in the last couple of years. He had been made redundant and had to sell. All seemed genuine to me at the time.

I have put on some 6000 miles in the last 12 months. Over the last few months there has been a mild buzzing & vibration through the handlebars and sometimes foot pegs. My local bike shop did the 12,000 mile service, test rode it but but said nothing to worry about.

I have now had another bike shop more used to Pans test ride it and they agree there is a problem.

They have balanced carbs, re-torqued engine bolts, gear box mountings, checked final drive shaft, and confirmed these and steering/tyres are all ok.

However they feel there is a knocking noise coming from the number two cylinder which they think may be a small end bearing rattle. To open up the engine is obviously a major task, does anyone concur with there findings?

Could it be anything else that could be more easily solved?

Or are they correct in saying it will only get progressively worse and could become a major failure.

Quite why it has happened is a mystery but either something has gone due to the bikes lack of use or the seller knew there was a problem there before selling to me.

Here's hoping that someone may be able cheer me up with some better news?

 

[wjbertrand]

Some light knocking noises are common to the ST1100, I wouldn't worry about it too much unless it's heavy or you can hear it whilst underway. I think some of the racket was diagnosed as due to some amount of end play in the cams, i.e. they are able to slide slightly fore and aft in operation. The consensus was that this was nothing to worry about. If it's a heavy, loud sound or gets worse than it is now, then I might investigate further. What weight oil are you running? Sometimes you can dampen engine noise using a slightly heavier oil (with mfr. recommendations of course).

As for the vibration, are the handle bar damper weights present? Is the sump over-filled with oil? Some folks have reported that causing a vibration. How well was the carb balance done, that can make a pretty big difference.

 

[sennister]

I have always run my 1100 a little low on oil. Still visible in sight glass but down in the lower 1/3. It seems to be smoother to me at least and I have read where other say the same.

 

[freeSTyle]

CARB SYNC,

With Carb tune or similar!

Don

 

[bdalameda]

If the sound disappates somewhat under load and increases at part throttle or slight decelleration the rod end bearings are loose. This would be a rare occurance on an ST1100. Loose small end if minor can run quite a while. I agree with Jeff - It could be the cam end play or simply loose valve clearance or valve guide. You definitely will pickup a buzz in the bars if the handlebar damper weights are removed. What weight oil are you running? Also - did they clean the carbs out or only synchronize them. You may have weak mixture on one cylinder due to restricted jets from sitting so much. I have seen carbs synchronized even with plugged jets.

Dan

 

[PeterW3035]

If it's a heavy, loud sound or gets worse than it is now, then I might investigate further. What weight oil are you running? Sometimes you can dampen engine noise using a slightly heavier oil (with mfr. recommendations of course).

As for the vibration, are the handle bar damper weights present? Is the sump over-filled with oil? Some folks have reported that causing a vibration. How well was the carb balance done, that can make a pretty big difference.

I'm not sure what grade of oil was put in, but I will certainly check the level as that does seem to be a suggestion that is often made.

I assume the carb balance was well done as that was one of the main areas they looked at, but I guess I can't be sure.

The vibration/buzzing in the bars is most noticeable after the engine has warmed up after say half an hour, 20 to 30 miles. Is that typical of carb tune or oil level?

The handle bar damper weights are present.

My big concern is that the knocking is symptomatic of some internal damage/wear and that by running it the problem will get worse.

Certainly the knock/rattle can't be heard when riding and is hardly discernible when stationary. The workshop said it was clearly there in that cylinder through a stethoscope?

 

[freeSTyle]

Peter* Is it more noticeabe at a specific rpm? Mine was similar as you describe. Mostly 2000/2500 mine had a knocking sound. At the time mine was under warranty and the dealer did some work on the carbs?? Problem STILL there?? With the tank cover off,it could be felt on the filter housing. A friend came over to help with mercury sticks.First sinc attempt with mercury sticks helped,but the noise was still there.Finally,bought a SK Flowmeter and with friend Reg Siemans (member here) help using the SK Flowmeter to sinc the carbs ALL is well.Thats been over 4 years now and NO more noise. If your noise is anything like mine was,maybe??

YMMV........Good Luck

Don

 

[STranger]

What about torn diaphram????

 

[PeterW3035]

Peter* Is it more noticeabe at a specific rpm? Mine was similar as you describe. Mostly 2000/2500 mine had a knocking sound. At the time mine was under warranty and the dealer did some work on the carbs?? Problem STILL there?? With the tank cover off,it could be felt on the filter housing. A friend came over to help with mercury sticks.First sinc attempt with mercury sticks helped,but the noise was still there.Finally,bought a SK Flowmeter and with friend Reg Siemans (member here) help using the SK Flowmeter to sinc the carbs ALL is well.Thats been over 4 years now and NO more noise. If your noise is anything like mine was,maybe??

YMMV........Good Luck

Don

I think I need to find a friend who knows what they are doing. The vibrations are certainly worse after a period at 3500 to 4000 rpm, typically a steady run on the motorway at 70ish.

I can certainly see the benefit of doing it yourself to be 100% sure of what's been done.

I used to have a good friend Honda Pete who looked after all my bikes and treated each one as his own, great guy and nothing too much trouble. Shame he has retired and hung up his spanner.

Thanks for the helpful comments, it seems to problem just needs further delving.

 

[PeterW3035]

What about torn diaphram????

Ok now you've lost me, diaphram where?

I am a total novice & ignoramus when it comes to all things mechanical, but see I may just have to get my hands dirty & learn (or at least keep picking your brains)

 

[the_gr8t_waldo]

i wouldn't discount the possibility that this vibration is being generated from wheel bearing(s) at least this is easyer to check.

 

[STranger]

In one of the carbs. I think the best bet would be to get a manual and a few tools. You seem like a pretty bright person...most of it is pretty common sense once your not scared to take it apart.

The reason why everyone is recommending the carbs is because the shared vacuum and the sync balances that vacuum. It make about the same delivery of fuel to all cylinders. If there is more or less fuel in a single cylinder it could cause problems like yours. Carbs on the st really are nothing more than a bowl of gas with a couple of jets that activate at different vacuum levels. If any of those jet are plugged it could create a lean situation which may be cause of your noise.

Good luck keep working on it...!!!!!

Jay

 

[saaz]

I get a slightly noticeable buzz at those revs as well. Smooth before and after. I have cleaned the carbs, synched them a number of times, and seems to be the best it can be. I have the slight idle noise as well, but this is not uncommon. The bike may just need a fair bit of use to clean it out, then do a carb synch or two along the way. I am going to undo and retentin all the engine mounting bolts when I do the timing bely, just to see it that might make a difference.

 

[Terk91]

I would guess the noise and vibration is from poor tuning - a cylinder is not pulling its full load. I would inspect the carb diaphragms, jets, wires, plugs and then perform a careful carb balance. When a cylinder is not in balance with others a knock at idle can be introduced in the vicinity of the lower right rear of the engine near the spring loaded damper shaft. The shaft has a spring loaded split coupling that apparently bounces when the uneven pulses hit it at idle. A buzz can also be introduced at varying rpm's from a carburetor that is not performing well.

 

[AZst1100]

just to be a jokester on this, it is missing 4 cylinders and they are in a V-twin configuration, they should be in a flat, opposed direction. Much smoother that way.

No problems here with my bike


I am reading all the ST1100 threads though, trying to learn what is normal.

bought one over in Cabot, Arkansas and will be headed that way to pick it up one day next month.