SOLVED!!!(?) Somewhat massive vibration under acceleration

Ok, I have a bit of a problem. Yesterday AM, my bike was running like a top. Smooth as silk. Parked it. Did some work at the office, then headed back out to visit a few vineyards. That first trip, I immediately noticed something was off. There was a noticeable vibration, especially in the footpegs and handlebars, and it is more pronounced under medium load. Like right when you feel the shaft drive switch from acceleration to deceleration, there it is. Regardless of speed, but it seems more noticeable over 25. No loss of power.

I've done the following in the recent past:
Oil change to diesel weight
clutch 2000 miles ago.
rear brake shoes
Steering head bearing
New shocks
New tachometer (spliced into a coil wire)


Here's What I've checked in relation to the above order:
No crazy amounts of metal in the oil. The occasional fleck on the magnet.
Clutch looked ok visually. It's pretty new, still, but there seems to be no out-of-the ordinary wear marks. There is a slight (1mm) amount of play in the basket as a rotation, but none up and down, or side to side.
Brake shoes seem fine. Broke in easily, doesn't seem like it would change under load.
New taper bearing was adjusted again and again until it was just right. Falls slowly without bouncing, but doesn't wander on the road. I backed it off 1/8 turn from "wander" and it seems perfect.
Shocks have no play in them, everything seems solid.
Tach- I cleaned and dielectric greased all the connections behind the headlight. I spliced into a couple spots, one being under the tank into a positive coil wire. Tack works great, and nothing seems to be lighting on fire. I pulled all of the plugs, and they seems to all be firing.

Here's what I'm thinking:

Coil grounding at higher RPM/vibration is shutting down half of the motor? I notice no loss of power, though...
Loose motor mounts? I'll try snugging everything up.
CV failure? Will inspect tonight.
Wheel bearings?
Swingarm bearings?

Any help would be appreciated, I hope to figure this on out...

 

Re: Somewhat massive vibration under acceleration

Look into the universal joint under the rubber boot where the drive shaft connects to the engine

 

Re: Somewhat massive vibration under acceleration

What do I look for? Any play or is some play allowed. I rotated the tire in neutral, and everything seemed smooth. I guess that doesn't say much...Also, I called it a CV...dumb.

 

Re: Somewhat massive vibration under acceleration

I notice you did Headset Bearings.

You have to Re-adjust those Bearings after a few-hundred miles.
They "Bed-in"

 

Re: Somewhat massive vibration under acceleration

Rick hit the most likely culprit based on what you have done.

Several other things came to mind too I recently went through a similar issue of vibration/tracking issues over appx 35 mph(http://www.xjbikes.com/Forums/viewtopic/t=43385.html). Mine was a result of a loose removable frame section (700's have a removable section for removing/installing the motor) and out of tolerance swingarm bearings.

inspect your frame/swingarm for flex/cracks/weak spots/bad welds
inspect your swingarm + swingarm bearings for side to side play (procedure in manual)
inspect your motor mounts for cracks/weakness/loose bolts
inspect your wheel bearings for side to side play (procedure in manual)

other unlikely but possible things:
damaged/severely out of balance tire(s)
low tire pressure
fork service/rebuild
fork oil
bad rear shocks (saw you just replaced, but possible you got a bad one)

also, after visiting several vinyards, was the nut that connects the handlebars to the saddle OK? (my sarcastic way of asking a very serious question)

 

Re: Somewhat massive vibration under acceleration

The head bearing has gone throught multiple re-adjustments over the past 500+ miles or so. The last one being about 100 miles ago. I think it should be okay, but I'll check it again. It's more by feel, but I think I have it pretty close.

The shocks seem to be acting normal. one side is not stiffer than the other, and they operate smoothly.

Handlebars are tight, no issues there.

I have a progressive spring kit, and will be installing that in the very near future.

Intuition tells me its a drive train issue with a bearing or u-joint. The fact that it starts IMMEDIATELY the moment the rear wheel becomes loaded seems indicative of something in the clutch/trans/driveshaft/swingarm/rear wheel. I'll do a good inspection after work today and report back. Thanks for all the help, I really appreciate it.

 

Re: Somewhat massive vibration under acceleration

This is also indicative of frame flex

 

Re: Somewhat massive vibration under acceleration

If you rev the engine in neutral does it still do it, if so at what rpm. A loose exhaust collector will vibrate like crazy under load.

 

Re: Somewhat massive vibration under acceleration

the u joint should have NO play. the splines on either end of the drive shaft should have no perceivable play but they move so they will have some.
is the vibration engine speed dependent or ground speed dependent ?

 

Re: Somewhat massive vibration under acceleration

+1 on uni joint. How many miles on this bike?

 

Re: Somewhat massive vibration under acceleration

I did a bit more work. The u-joint is tight. No play. It's rusty, but there is no movement whatsoever. On the center stand in neutral, rotating the tire about 10 degrees either direction produces a little play, but this seems normal. I got the clutch covered up again, and went through the revs in neutral, there doesn't seem to be any symptoms. I click her down into first and let the clutch out. Examining the rear tire, it seemed to rotate just a bit off. There doesn't seem to be any play at all in the rear swing arm or hub, so it seems like it's an out of balance tire. Would that make sense as something that changes under LOAD? I guess it has to be. The tire has maybe 3000 miles on it and is in great shape. Would remounting it help?

 

Re: Somewhat massive vibration under acceleration

On the U-joint: By rusty, do you mean surface rust, or rust in in and around the bearings? Rusty bearings will cause the U-joint to bind, which will cause a vibration. The joint should have no lateral play (along the joint pins), but it should rotate freely (along the joint axis) with just a little resistance from the grease.

An out of balance, or out of round (a tire can be in balance and still not be round enough to actually be IN balance) tire will cause a vibration that increases as road speed increases.

 

Re: Somewhat massive vibration under acceleration

A U-Joint Problem would "Clink" or "Ring"

Everyone should inspect their U-Joints and do Preventative Maintenance to the Rubber U-Joint Boot.

Lube the Springs on each end.
Open the Bellows and drain any water or moisture.

If you FIND water:
Drain
Let Dry after Paper Toweling the Bellows.

Inspect Bellows DRAIN Port.
Keyhole-shaped protuberance at the Rear-bottom of the Bellows.

Often, ... the MEMBRANE from the Mold is still in place sealing the Drain Hole.
If your Drain Port is still closed-off, ... Puncture it with a Drill Bit and Open the Port so the Bellows won't collect moisture.

Treat with ArmorAll ... or your favorite treatment.

 

Re: Somewhat massive vibration under acceleration

I guess I should describe what happened a little more. When I put it in first while it was on the center stand and revved it up, the bike was bucking all over the place. So that rules out anything motor/clutch related. To be honest it felt like it was coming from the rear wheel. Closing one eye and looking down the rim as it spun, the line seemed to stay true in reference to the bike. When I did the same on the tire, that was not the case. Obviously, tires have some defect in them, but this seemed to be quite a bit of movement. I'll have the shop who put it on check it. I find it very strange that something like this would just "come up". Could I have hit a pothole or something too hard and busted it internally?

 

Re: Somewhat massive vibration under acceleration

And as far as the SPEED at which it happens...

Again it seems more pronounced UNDER LOAD. The moment at which the tire switches from slowing down to driving.

That being said, the speed at which it occurs is throughout the whole range(under load). It seems most pronounced around 20-40mph range, until it smooths out up around 60. It's still there, but is at such a quick frequency that it kinda blends together. I probably wont be going up to 60 again until this gets sorted... 8O

 

Re: Somewhat massive vibration under acceleration

How old are the tires?

 

Re: Somewhat massive vibration under acceleration

This year. Pretty darn brand new Dunlop 404's. Well, I got them this year, and the size had to be ordered from the local shop, so I'm assuming they're not that old.

 

Re: Somewhat massive vibration under acceleration

Again...how many miles on this bike?

 

Re: Somewhat massive vibration under acceleration

check the age of the tire via the date code stamp on the sidewall.

should be a 4 digit number indicating year and week it was produced

ie. 1246 would be the 46th week of 2012 thats the only way to tell how old the tires really are.

 

Re: Somewhat massive vibration under acceleration

Sorry, mileage is 24,000. I'll check the code today. I think my best bet at this point is to bring the tire to the shop, have them remove, inspect, and rebalance it. And wile it's off, do a more thorough inspection of the shaft and free play in the system.