5k rpm vibration

My 82 xj650j feels like its vibrating accelerating past and decelerating at the 5k mark. I know there's been some previous talk about this but I was wondering if anyone found a for sure solution to fix this problem.

 

Carb synchrinization eliminates most of it. The buzz is a nature-of-the-beast thing.

 

I recently added bar weights to my bike, helps a lot with vibrations, the engine is solid mounted so.... Yeah

 

Also, just to ask, at 5000 in top ger on the highway? Or in all gears, if only on the highway it could be a harmonic vibration if the bike has a lot of highway miles at roughly that RPM not the motor.

 

It vibrates in all gears at 5k. It seems to go away once the rpm's are above 5k but vibrates on decelerating and getting down to 5k also. It didn't Used to do it before I broke an exhaust manifold bolt. And removed the exhaust and re-installed it.

 

I appreciate all the help

 

Maybe the exhaust is touching the frame somewhere and causing it... Idk?

 

Other than that you randomly picked up a fuelling issue at the same time

 

I will definitely check the exhaust and let you know. It seems like I caused it somehow. I never had this issue before I broke the exhaust manifold bolt and removed the exhaust pipes. Ive removed the pipes before and reinstalled them with no issues. i could run the bike pretty if hard if I wanted too without any issues.

 

What exactly are bar weights? Im not familiar with them.

 

The 5k ‘harmonic buzz’ is a documented phenomena- not a vibration as much as a sensation. I feel it in my left foot peg the most.

 

I guess you could call it a buzz but it sure feels like s vibration. It resonates thru the whole bike and thru your body.

 

You guys are the experts I'm new to this bike. So I appreciate what ever info you have to offer.

 

I'll check back gotta work tomorrow.

 

Bar weights are long shafts of steel with rubber plugs not the ends just bigger than the metal that slide into your handlebars, some (like mine) also have 1 or 2 o rings in the middle.
The idea is that when the bars try to vibrate and cause carpal-tunnel syndrome instantly, the weights try to, and seem to very well, counteract that vibration and minimize it.
I'm not a scientist for the expaination, but they did seem to help.

 

Anyone wants to buy me a set of grips, I'll cut em off and post a picture of the weight... Lol!

 

I was looking at my bars, stock grips... could I cut a hole in the end and mount the weights or does it require new grips?

Just a comment... I always thought of this as "My bike vibrates at 65mph but it's surprisingly not as bad above that". I wasn't even thinking of engine RPM and thought it was just part of having an old bike, tire balancing, etc. I just watched the tach on my way into work and sure enough it's 5K. In large propulsion diesels and gas and steam turbines (my background) there's something called "barred speed". It's the speed at which the engine gets in the harmonics zone and will eventually shake itself to bits if you try and operate it there. The design engineer's job is to ensure this happens outside any range that the machine could be operated at in doing it's job, and it's the operator's job to transition through this speed as quickly as practical.

Since my speedo redline is 55 mph as was the speed limit in 82, I just wonder if the design guys took some liberties and figured "65mph is fine as they are not supposed to be operating there anyway..."

Things I'm distracted with on a Saturday at my desk.....

 

The cap at the end of the grip holds the weights in, you have to replace grips, or I guess a blob of silicone, but that's ugly.
Emgo sells a foam type soft grip for like $15 also reduces vibration a bit, plus they have cool gold Eagles on the chrome end caps!

 

I Won't get a chance to look at possible issues that could be causing my problem until sunday night after work. I was just trying to compile as much info as possible based on everyone's experience and expertise to help me in solving my problem. The bar weights are interesting. The strange thing is I didn't have any vibration or buzz at any rpm before I broke a manifold bolt.