Pulsing drone vibe

[cupidstunt]

Have a strange oscillating drone vibe at certain revs, (every second or so), but feels cycle rather than engine related, if that makes sense.
Bike is new to me from last October, and it was there before I changed swing arm...
80k miles, and good service history, noticed the rubber drive cushes were a little worn, but nothing too bad, and doesn't clank on take off...
Anything else to look at?

 

[Nashcat]

I has a pulsating drone from a set of Metezler tires, several years ago. The different tread spacing between front and rear set up a harmonic vibration.

John

 

[Uncle Phil]

Maybe needs a carb sync?

 

[jfheath]

Wind in the plastic radiator grill - grill not fitted securely. Sounds like tyre riding over wet tar.

Wind in any other part of the fairing, not properly secured. Check interlocking tabs at fairing joins

Twang the edge of the heat shield on the front down pipes - should be a clear ring. You can do it by reaching up under the lower front cowl. Cold engine is advised.
(if cracked, tends to happen between 2k and 3k rpm).

(None of these are specifically 'cycle' related - but they do come and go with bike speed, wind direction, so worth consideration anyway)

A combined sound caused by an odd patch on both tyres hitting the tatmac at the same time. Different diameters. Its possible that the same patch on both wheels would hit the ground every second or so at certain speeds. (Quick thumbnail calculation). If that was the case, then the 1 second interval woul increase as you slowed down slightly, so that could be easily confirmed or eliminated.

 

[cupidstunt]

i'll get better data on speeds and revs later. plastic fittings all sound, heat shields absent.

 

[Uncle Phil]

i'll get better data on speeds and revs later. plastic fittings all sound, heat shields absent.

Heat shields absent? I'm surprised you don't have some melted lower fairings!

 

[Nashcat]

Ride down a long, steep hill so you don’t lose speed and pull in the clutch. If the drone quits, it’s engine/drivetrain related. If the drone continues, it’s tire or bodywork.

John

 

[ibike2havefun]

Huh. This is a thread about a motorcycle issue- not what I expected at all, based just on the title.

 

[Catmandu2]

The Metzeler Z8 rear tire has a documented history of it's tendancy to have a resonate or harmonic vibration. It's not every z8 hwm rear tire that exhibits this,, it happens randomly. They are prone due to the variable tensions employed in it's cord materials, as described on Metzelers web site. Different models of heavy sport touring bikes have reported the same thing. My vibration cleared up after about 4 or 5k km's as the tire wore. I would never by another Z8 rear. However,,, the Z8 front tire is the best front tire I have ever had. I use it all the time on both bikes,,, and have a couple of spares in the basement for future use. So,, the question is,,, are you running a z8 ?? CAt'

 

[ASPC]

Yes on the Metzeler Z8. Rear tire vibration below 4K RPM. Best front tire there is IMO.

It looks like they have stopped selling the Z8 and all front tires in our size.

Could also be out of balance tire of any brand.

 

[cupidstunt]

Heat shields absent? I'm surprised you don't have some melted lower fairings!

20C temp here maybe 5 days in the year...

 

[Bikeric]

I had a 500 Honda back in the 1970s which set up a drone or a buzz at certain revs.. It turned out to be the rear number plate vibrating - an extra screw stopped the vibration and noise. Worth a look perhaps.

 

[red one]

From time to time my 24 year old 1100 might exhibit a strange noise or two but as long as it's running ok i have no concern. Even human beings of the senior citizen age have been known to make stange noises too

 

[Bikeric]

From time to time my 24 year old 1100 might exhibit a strange noise or two but as long as it's running ok i have no concern. Even human beings of the senior citizen age have been known to make stange noises too

No names, no pack drill!

 

[Catmandu2]

It looks like they have stopped selling the Z8 and all front tires in our size.

Well that's sad,,, but not unexpected. I started hearing, about two years ago, that the Z8's days were numbered. I have enough Metzeler product on the shelf to get me through 2024. So,,, there is time to find a new favorite set. Metz has been good to me,, but I expect premium performance from premium priced tires. Will be looking closely at the T32 gt line,,, for 2025. CAt'

 

[cupidstunt]

After investigation, its an engine vibe. Starts just over 3k rpm and continues to after 4.5k. (pulled clutch in and no difference)rdly prone to
I have dropped engine oil, and synced carbs to no avail... Would it be prudent to rebuild the carbs? (81k miles and no previous notes of carb rebuild)
The cranks are hardly prone to bending?

 

[Al st1100]

After investigation, its an engine vibe. Starts just over 3k rpm and continues to after 4.5k. (pulled clutch in and no difference)rdly prone to
I have dropped engine oil, and synced carbs to no avail... Would it be prudent to rebuild the carbs? (81k miles and no previous notes of carb rebuild)
The cranks are hardly prone to bending?

not to fix an engine vibration

 

[Roger]

Have the carbs/exhausts been messed with? 3k was when my Motad exhaust had a 'one note' that was an aural nuisance. I reckon it's a little lean and maybe you have a flat spot..........

 

[Larry Fine]

After investigation, its an engine vibe. Starts just over 3k rpm and continues to after 4.5k. (pulled clutch in and no difference)

That sounds contradictory; if there was no change when you pulled the clutch (and I presume let off the throttle), then it's road-speed-related and not engine-RPM-related.

To me, that suggests tires and/or wheel bearings, or the drive-shaft/rear end. And remember, STs do drone quite a bit. Is this an 1100 or a 1300?

 

[cupidstunt]

Definitely engine vibe. like a pulsation. just reving on centre stand does it...