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I hope someone has some clue why this is happening. Recently I have noticed at speeds over 85 to 90 miles per hour there is a rhythmic vibration coming through the handlebars. It is predictable and repeatable and happens constantly over a certain speed. You can actually see the mirrors vibrating as this occurs -there will be a strong vibration for a second or 2 followed by an equally long smooth period. Any thoughts?

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Possibly a tire balance or out of round issue.

 

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My 6th gen had a similar issue though also just shaked over 80 mph. Mine turned out to be front wheel alignment. Once aligned slowly went away as tire was by then worn by issue. Put a new tire on and no more shake or rhythmic vibration.  

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My 6th gen had a similar issue though also just shaked over 80 mph. Mine turned out to be front wheel alignment. Once aligned slowly went away as tire was by then worn by issue. Put a new tire on and no more shake or rhythmic vibration.  
Brand new tire.

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I've seen a situation where after installation of a new tire the chain was slightly overtightened.  This caused a vibration similar to what you're describing.

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After the alinement didn't seem to work then as the tire wore it got better and better. I then put a brand new tire on and problem was solved. IF this is your problem you may not have ruined your tire yet. I'm no expert so no promises this is your problem just a possibility.  

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2 hours ago, interceptor69 said:

Brand new tire.

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So has it only happened since the new tire? Could well be possible they forgot to balance it! Agree with GreginDenver, have also experienced strange vibrations with a friends bike caused by an over tightened chain.

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Aye, check the chain and sprockets

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The front tire is new- the rear about ayr old. New sprockets and chain last year. So a too tight chain can cause a front end shudder? There are several weights on the front so it appears balanced. Also it started last year before I put new sprockets and a new chain on last summer.

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1 hour ago, interceptor69 said:

So a too tight chain can cause a front end shudder?

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Too tight chain will moan under the stress... never experience a shudder because the rear sprocket cush drive absorbs any vibrations from migrating to the front...

 

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More info:  the vibration started a year or so ago-so 2 front tires and the same problem.  today took a ride and noticed the vibration occurs even when the clutch is pulled in so not related to the engine.  I have some GoPro video shot of the mirrors at around 90 mpg-I can see it while riding but couldn't tell much looking at the video.  The odd thing is the vibration slowly builds in intensity, peaks, then decreases in intensity and it doesn't seem to change duration even when speed increases or decreases.  I will try to attach the 2 short vids.  I was staring at the mirror on the 2nd vid and wasn't watching the road as closely as I should have....

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I'd be checking to see if there was a wheel rim out of round. Can't think of anything else!

"2 front tires and the same problem"! What was the wear pattern like?

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Have you done a front wheel alignment? It's simple free and takes just a few minutes. 

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7 hours ago, Grum said:

I'd be checking to see if there was a wheel rim out of round. Can't think of anything else!

"2 front tires and the same problem"! What was the wear pattern like?

the wear pattern was very "A" shaped when worn, but symmetrically worn.

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6 hours ago, thepretender said:

Have you done a front wheel alignment? It's simple free and takes just a few minutes. 

No, never done that-how is that done on a motorcyle?  

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1 hour ago, interceptor69 said:

No, never done that-how is that done on a motorcycle?  

Curious to know the technique. Only thing I can think is to loosen the triple clamps to make sure the axle holes are in line as opposed to having the tops dead level. I've been told that is the best way to set up your forks.

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duc2v4 did the actual work but it goes like this. Put bike on center stand push down on rear to lift front end (this was the extent of my help lol) loosen one side of the triple tree lower one on 1 side I think he also loosened the mud guard and brake and possibly the the axel. Then compress the front end a few time bounce it aggressively. If there was a problem this will correct it then tighten the triple tree. If I miss anything duc2v4 or someone else can correct me.  

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Delboy does a good job of explaining the process as well as providing a video you can watch. The start of the process starts at 4:15.

 

 

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That was a brilliant video, thanks for posting it.

 

I rebuilt the entire front end on my 97 this Spring, and by reading and trial and error finally got it right when re-assembled.

 

But nothing I read was as clear and concise as this was.

 

+1 ! 

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At this junction I'd eliminate the items listed in the VFR shop manual...

 

TroubleShootingHandling.JPG

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When you say rhythmic vibration, do you mean harmonic vibration ? This is when slightly out of balance parts vibrate in harmony with other parts thus producing a rhythmic pulsing effect, sometimes enhancing the effect & when out of sync suppressing it.

 

I would check both wheels are balanced correctly, then check your head race bearings, front wheel & rear hub bearings to ensure there is no play there. Also check your front spindle & swingarm spindle/bearings. Check your wheels spin freely at both ends with no brake drag. If you have brake drag then check out your callipers first. Last but not least check your wheel alignment.

 

 

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When you say rhythmic vibration, do you mean harmonic vibration ? This is when slightly out of balance parts vibrate in harmony with other parts thus producing a rhythmic pulsing effect, sometimes enhancing the effect & when out of sync suppressing it.
 
I would check both wheels are balanced correctly, then check your head race bearings, front wheel & rear hub bearings to ensure there is no play there. Also check your front spindle & swingarm spindle/bearings. Check your wheels spin freely at both ends with no brake drag. If you have brake drag then check out your callipers first. Last but not least check your wheel alignment.
 
 
It's rhythmic in that the vibration occurs consistently above a certain speed at a predictable interval with a specific and constant duration. The vibration builds over appx .5 second, lasts appx 2-3 seconds then dissipates over appx .5 sec. There is an appx 2 second pause then this repeats. Doesn't matter whether the clutch is pulled in or not. The speed of the bike doesn't cause the interval or duration to change.

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OK the fact that it comes and goes is harmonics. If the engine is allowed to idle with clutch in rolling at speed & this is still happening then it’s likely the drive chain & sprockets causing the harmonics &/or the wheels. The stock 17/43 gearing means the front sprocket rotates 2.3 times for every one of the rear. Plus as chains wear they create slack areas.

 

You said this has persisted over tyre changes & before latest chain & sprockets. Then it’s likely to be wheels balance &/or worn bearings combining in a harmonic frequency. Just because tyres are X years/miles old & were balanced when new does not mean they stay that way or the tech that did them did a good job. Check all bearings & then remove both wheels & have them re balanced. While the wheels are off have your head bearings checked & regressed, when were they last done !?

 

 

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Take your bike and whilst riding around 40 mph in a straight line... let go of the bars. Do they start into a headshake? This is a classic sign of worn out steering head bearings.

 

Mine were shot before 12k miles (when I bought it). Just had my ZRX experience the symptom from above and sure enough... with the front end off the ground I get some play.

 

 

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