Possible Drivetrain Issue? - Vibration

[twdurdentwd]

Okay. This vibration used to be mainly a "decel" vibration under the condition where I roll off the throttle 1/2 way without pressing clutch and allowing the drag force to "rest" on drive train. The vibration would happen in mid to high speeds, but at high speeds, the vibration would also happen with throttle released 100% as well.

So... This vibration had gotten worse and I can pin point exactly what I did to cause it to become remarkably worse. The weather told me that I should go fast.... so, cruising at 120, there was a point where I had to release the throttle altogether and rather suddenly without pressing the clutch, the vibration became a lot worse at this time.

Now the vibration will happen upon ACCELERATION NEARING 100mph and it's an alarming vibration.

What do you guys think?

[slider]

had a problem  almost like yours....replaced u-joint and problem  went away...

[twdurdentwd]

Did you also sort of have a "slack" in the drivetrain that could be felt when rolling off and on throttle at any speed?

[Firefighter]

I don't have enough info, like when you pull the clutch does the vibe change? Does the vibe speed up with engine rpm or wheel rpm? Everything look OK, tires, etc., etc?  Might not ought to ride 120 mph if you don't know what is causing your vibration.  Firefighter

[twdurdentwd]

Before it began vibrating on accel, it vibrated more when pulling the clutch... It's definitely not with engine speed

[Louis Durocher]

I would check the ujoint ,coupler and drive shaft. I Had to change all three.
Good Luck

[F6Dave]

When I bought my '99 IS with 6800 miles it vibrated when I closed the throttle at highway (70+ or so) speeds.  I put up with it for a few years, then changed the U-joint at about 50K miles.  It made no difference at all.  Now, at 95K miles the vibration is exactly the same so I don't worry about it.

My '98 Tourer has 175K miles on the original U-joint.  I can feel a very slight (barely detectable) vibration under the same circumstances, but it too hasn't changed noticeably in all those miles.

It could be that many Valks have this issue, some worse than others.  There was a post here a few years ago claiming that was the case.

While I haven't had a U-joint fail on any motorcycle, I have in a car, and the vibration became very bad very quickly.  I would think a bikes U-joint would fail quickly as well.

[Firefighter]

Have you had the wheels off the ground and try to see if any thing seems loose? Wheel bearings, swing arm, shocks, brakes and calipers, etc. I think after that I would be checking u joint, drive train, and  maybe dampners.     Firefighter

[John Schmidt]

Doing 120, or even 100 for that matter is foolish....whether you have a vibration or not. And, dumping the throttle at those speeds as you described puts an enormous strain on everything from the timing belts all the way back. So if something happens to the driveline while you're "testing" various theories as to the source of the vibration, please wave as you fly over the house(the bike will still be in Sebastian)....it's the courteous thing to do.

[Willow]

What has been described sounds an awful lot like a pinion gear connection beginning to fail.  It could also be a U-joint.

Pull the drive shaft and you should be able to see whether there is excessive wear on the gear.  If there is you should likely change both the shaft and the gear in the pumpkin.  It's not a really expensive repair but can be real annoying if you wait for it to fail under load.

[Chrisj CMA]

Carl is right, but its not a gear in the pumpkin.  Its the Pinion Cup and drive shaft that is the usual offender.

[twdurdentwd]

Please forgive me for the naivity, the pinion cup is what accepts the driveshaft on the differential, isn't it? And how is out removed from the differential?

[John Schmidt]

Please forgive me for the naivity, the pinion cup is what accepts the driveshaft on the differential, isn't it? And how is out removed from the differential?

Correct, and I just used a rattle gun(impact wrench) on the nut in the center of it to remove it.

[twdurdentwd]

Great, thank you

[Brian]

I have highway foot rests mounted on the engine guards. For years I would feel a strange bumping or vibration when using these during deceleration and accelerating at highway speeds and only when using the pegs. I ordered a set of OEM dampners for the rear wheel just to have on hand. During a spring maintenance inspection and lube of the drivetrain I decided to check the original 97 dampners. There was slop in them, so out they went and the new ones went it.  Problem gone for two riding seasons and now starting to come back slightly. The new ones are really snug in the wheel when new. I suspect that prolonged use of worn dampners would cause excessive wear on the other driveline parts especially the u-joint.

This year I plan to check the dampners again. If there is slop I will see about using some kind of  gasket paper or other material to act a shim all the way around the dampner verses buying new at this time.

[art]

I had the same problem for years and part of the problem was a bent drive shaft. It had 1/16 run out when checked in a lathe and dial indicator. If everything else checks out have a machine shop do a run out check. It can be straightened in a press by a machinist.

[twdurdentwd]

Okay, so dampeners, pinion cup, shaft, and u joint/yoke. Out with all old and in with new. Screw it.

[Bighead]

No one said out with all the old and in with all new they are just giving you suggestions
it is very obvious that no one can tell you for sure what is wrong without looking at all these components.

[twdurdentwd]

If I do it all, I won't have to worry about it for a while. I know for sure though the dampeners could be replaced because they aren't snug and can be wiggled... So might add well do it all

[Ricky-D]

Individually, the dampers are each loose fitting, but taken as a whole

with the flange inserted you will find little looseness. There is some, but

very little.

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