annoying engine vibration at 3900 - 4500 RPMS

[maro]

Thanks for all the insight folks. Don, what do mean exactly 'tank flap"?

vibrating fuel tank flap situation.

[hampshirehog]

Thanks for all the insight folks. Don, what do mean exactly 'tank flap"?

Don's talking about his 550 - that has a fuel filler cap on the tank that you access by lifting a hinged flap. You haven't got one of those on your 1100 but I think Don was just suggesting that you might find the cause of the vibes where you would least expect it and that it might be a really easy fix.

[Big T]

It's just one of those annoying things that will take some time to find

It's not a twisted crank, so breath easier

[maro]

man I really hope it's not. I want to assume that a twisted crank would create nasty vibes in most ranges. again, it happens only really in the 4000 range. I check horn mounts, they seem ok.

It's just one of those annoying things that will take some time to find

It's not a twisted crank, so breath easier

[derwood]

doesn't take long to look at the Clutch.......

[duaneage]

I invited Josh to my elaborate garage Friday night, we'll check the valves and sacrifice a live chicken and get to the bottom of this. OR a bottle or two.

[Big T]

man I really hope it's not. I want to assume that a twisted crank would create nasty vibes in most ranges. again, it happens only really in the 4000 range. I check horn mounts, they seem ok.

Yes. but are they vibrating noticably at 4k?

[Big T]

I invited Josh to my elaborate garage Friday night, we'll check the valves and sacrifice a live chicken and get to the bottom of this. OR a bottle or two.

I think a laying on of hands is the proper treatment

[duaneage]

I thought about unhooking the tach so he doesn't know what speed it vibrates at. And doing the speedo so he goes 85 everywhere, that should take care of it.

I need to ride it to get an idea about the problem. My 650 bounces the RH mirror at certain RPMs, it's a trait they all have. I'm thinking maybe a motormount is loose or something like that.

[maro]

I thought about unhooking the tach so he doesn't know what speed it vibrates at. And doing the speedo so he goes 85 everywhere, that should take care of it.

That my friend is a good call.

[gearhead13]

I found that MY vibration amplifier is my license plate, a couple zip ties should fix it

[Griffin]

The exhaust heat shields are also a source of buzzy noises when an engine is spinning in its vibration range.

Just about every air cooled inline four I've owned (and I've owned a bunch) had a range where the harmonics created a buzz. Some were worse than others, some were barely noticeable.

My 1000G has a vibration that's barely noticeable by feel, but the fairing mounts buzz between 3600-4100 rpm.

[Shin-Ken 1074]

Interesting situation regarding the vibration you have at 4000 RPM. My 82 GSX1100 and four other 82 GSX1100 I know of have the same issue with the vibration coming in at about 3,950 RPM and then just as suddenly disappearing at about 4,100 RPM. I am thinking it is maybe just one of those things that some of these early 1100 engines have and it could be nothing to worry about. Why do I think that? Well, the five engines I mention have had the same vibration issue from when they were new bikes in 1982, each of the bikes are still on the road 30 years later without having an problems. All of the engines have over 150,000 km on the clock with two having over 400,000 km and only ever having had the valve train overhauled in that time. I am not saying your vibration isn't being caused by something else just that it seems not that rare with the early GSX1100 engines and it might not be a problem. Good luck with your investigation, cheers.

[maro]

update

So duaneage and I both tried troubleshooting the issue. all valves are in spec. carbs synched. I replaced all spark plugs. We even checked with chopsticks to see if the crank was twisted and it doesn't appear to be. I removed my case guards thinking they were causing a vibration.

Unfortunately the problem still exists. The intense buzz / vibrations still happens in the 3800 - 4300 range and you feel right under the seat.

not sure what else to do aside from a carb clean. Though according to my plugs my carbs are working just fine. I pull fine in all ranges too.

I don't remember this being an issue a few years ago. maybe I'll use some magic seafoam and pray to the gs gods.

[maro]

Problem solved

On my way to work this morning I decided to swap out my stock seat with my corbin, just to see if it made a difference. IT DID. While sitting on the corbin (which is usually the less comfortable choice) there was almost no vibration in the 4k range or through any of the ranges.

Tonight I will check my seat mounts on the stock and see what I can find as the culprit, perhaps rubbers or release.... whatever it is, it was causing this issue.


thanks to everyone who helped me troublshoot this issue. Of course I tried the easiest thing last, but hey, it worked.