Experienced VFR diagnostic/mechanics needed: EXTREME vibrations coming from???

I have an issue with my VFR that originated quite a while ago. Long story short I have a harsh vibration which seems to originate around the pegs and then transfers throughout the bike including the seat and handlebars.

THIS IS NOT THE NORMAL VFR VIBRATION. This is without question an issue that has developed over time. It's not the tires, not bearings, all motor mounts are tight, chain and sprockets are new, blah blah blah.

I have been able to verify the vibration by riding another 6th gen bike recently. The other owner agrees also. His quote was something feels "loose".

To describe the vibration, the best I can say is when the motor is under load such as climbing a hill or chugging in a lower gear, there is a feeling of play somewhere in form of a binding, "chunking" kind of sound. To me it feels like there is a bearing bad somewhere internally along the driveline. It's hard to tell for sure if it's getting worse. I'm paying a lot of attention to it right now which always exaggerates things.

Other then this issue, the bike has been ridden many, many miles without incident with these symptoms. MPG hasn't suffered or anything. The bike has been run pretty hard during my ownership but I've also maintained it very well.

I guess I'm stumped. Anyone have a similar issue?

Thanks!

 

This is a long shot but have you kept up with the valve maintenance? On my 5th gen at around 5-6K RPM it would get real vibraty almost like a paint can shaker. But after doing the valve adjustments the engine runs real smooth through the redline.

 

My initial reaction is no f'en way but at this point I will not rule out anything. I can't possibly see how a valve even way out of spec would cause a vibration that seems to originate so low in the motor. There is no abnormal noise coming from the valvetrain. If the valves were the cause, I would think a noise would be pretty prevalent like a broken spring or something.

Then again, what do I know?

 

Check your chain thoroughly. Sounds like one or more binding links to me.

 

ck chain for tight spots, ck rear swingarm hub and swing arm to engine piviot.
put bike in neutral and coast to see if vibration goes away.
bad or broken motor mount.
poss something inbetween rim and swingarm or weights feel of rear tire.

 

Do you notice the noise at idle at a stop, or just when rolling?

If just when rolling does it vary with engine rpm or speed in mph?

Does the noise change if you pull in the clutch and just freewheel?

If you kill the engine while rolling and coast with a dead engine, do you hear the noise?

 

I tend to think along the same lines as Joey_Dude, particularly since it has developed over time. It may not be the valve clearances specifically, but it could be one cylinder not producing as much power as the other three. It could be valve clearances, spark plugs, fuel injector or a combination of items.

 

The chain is not the culprit. It's brand new and has no tight spots. I changed it in hopes that this would solve the issue. I guess I will have the valves checked and go from there. I was also reading about a starter valve sync. Could be next if the valves don't cure it. I still have a hard time believing the valves could cause such a dramatic vibration but like I said, what do I know?

 

Well, it's not so much the valves specifically, per se. If you have one cylinder that is making 25 HP, one that is making 18 HP and two that are making 21 HP, that will cause mechanical vibration under load.

Granted, what you are describing does sound more like a drivetrain issue than an engine issue, but multi-cylinder engines that are not producing even amounts of power can feel pretty bizarre. It's kind of like having a V8 automobile lose one cylinder. It goes from being smooth and powerful to rough and gutless. And that's only one cylinder out of eight.

 

From what you describe, it makes me think transmission or chain & sprockets.

Does this occur in every gear? With the clutch in & coasting down to a stop? Rolling off after accelerating? Floor it on a staight & roll off quickly to check. If you can do so safely, speed up until this occurs & then pull the clutch in & hit the kill switch. Do the vibes go away when the engine shuts off?

If it that doesn't narrow it down, that leads me to suspect your recent chain replacement. First, if you didn't replace the sprockets with the chain, that would be a prime suspect. I would put the bike on the center stand, pull the clutch slave cylinder off & take a look at the counter shaft sprocket. The symptoms you describe sound like the counter shaft sprocket is loose or bad.

KC-10 FE out...
lane: :usa2:

 

Consider that the starter valve synchronization is MUCH easier than the valve adjustment. My advice is to do the valve sync first and see if that offers any improvement. VFRD has a cool cheap set of instructions on how to do this: http://www.vfrdiscussion.com/forum/lofiversion/index.php/t16200.html

After doing the starter valve sync if you do notice it getting smoother then you know it's the valves. Then the next step would be the dreaded valve adjustment.

 

The chain and sprockets are new replaced at the same time. The problem existed prior to and after the installation. The vibration occurs in every gear under load. Not specific to one gear. I'll have to do some experiments like you guys have mentioned. I'm replying with an iphone right now during a track weekend. I'll elaborate more when I get the chance.

Thanks for all the suggestions so far!

 

As of Tuesday night the VFR will be under the knife getting the valves checked. I guess we'll see what luck I have. After that, I'll have to do some further diagnosis based on the other feedback you guys have given.

Again, thanks for the help!

 

Rubber isolators in the cush drive hub?

 

Went to check in on the progress last night. So far 3 of 4 valves in the rear are tight. Front cylinder hasn't been checked yet. I'm guessing the same situation up front.

 

There has been one recorded incident of a bent and cracked REAR axle. It causes a visible wobble of the back tire.

Just another thought...

 

Gotcha, it's starting to sound likely the valves are the culprit. On my bike I had 8 valves out of 16 too tight. Most of them were intake. I'm curious to hear how the adjustment affects the bike!

 

two4one: could you let us know what the final outcome of the valve adjust was, both number of valves out and if that fixed the vibration?

I'm curious as I have a new-to-me 2000 with noticeable vibration in the same RPM range Joey_Dude mentioned. I have no service history with the bike, so I don't know if the valves have ever been done (approaching 23k now).

Thanks!

 

Good timing on your post aaastone. I just had the chance to ride the bike for a thorough evaluation yesterday after the valve adjustments. Long story short is there has been no improvement in regard to my vibration AFTER the valves were adjusted.

The majority of my valves were tight or nearly out of spec on the tight side. I don't have the numbers unfortunately.

At this point I'm going to continue to evaluate the driveline. There's an answer here somewhere. It's too dramatic to not have a solution.

 

Thanks for the update, sorry to hear that the problem isn't solved yet!