Rear Vibration

[Aequitas4]

Now that the bike is up and running well, thanks to lots of help from you guys, I am noticing a intermittent vibration in the seat that seems to be coming from the rear wheel/gearbox area.

It happens above 50 mph and vibrates for about .5 seconds and repeats every 1.5 seconds. Below 50 I don't really notice it and above 70 it almost feels constant so I don't think its any kind of resonance. Otherwise I would only expect it at a specific speed/rpm based on the motor/drive wheel.

This vs1400 is a hard-tail on solid rear suspension and is running factory pro jets, pods, cobra drag pipes and homemade lollipops. Tires are new and were balanced at the shop the mounted them. Rear gearbox oil was just drained and refilled according to the service manual. I'm considering changing the rear wheel bearings (probably need to be done anyways with 85k miles) but my other concern is the alignment of the rear wheel in the swing arm. The wheel appears to be in line with the backbone of the bike but not in the center of the swing arm (wheel appears to be way to the left in the pictures below). I've seen post about Harley rear wheels not being centered under the fender but this looks very strange to me.

Only other ideas I have are bad throttle/carb sync or rear brake vibration Any thoughts? Is this normal?

[FallenAngel]

Check your Universal joints

[Aequitas4]

Should I checking that they are greased or am I checking for wear and replacing as necessary?

[FallenAngel]

Check for wear
I would remove to propeler shaft and move to U Joints through all its motions checking for sloppiness(??)
by twisting
Check the spline that goes into the transmission for wear and that it has grease
and check the the pinion and the rear wheel

Also check your rear whelel when re installing it Make sure you get it tight and in line with the front wheel

[Aequitas4]

Great! I'll try that. I haven't seen anything in the service manual for rear wheel alignment. Is there adjustment to get it in line with the front wheel if its not right?

[Herb]

Check for wear
I would remove to propeler shaft and move to U Joints through all its motions checking for sloppiness(??)
by twisting
Check the spline that goes into the transmission for wear and that it has grease
and check the the pinion and the rear wheel

Also check your rear whelel when re installing it Make sure you get it tight and in line with the front wheel

I will add that where the propshaft goes into the rear end has a a joint also and they have been known to fail. Mine failed at about 190,000 miles.

The way it is made the joint moves in and out and the splines wore out. The manual has instructions for removing the seal and the shaft.

You may have already changed the grease in the rear end but I found that mixing the grease with 1/2 STP made the thing run cooler and smoother.

I almost forgot to answer you question about wheel and swingarm alignment. Yes, the wheel is offset to the left but it is in line with the front wheel. Suzuki make the right side of the swingarm wider to accommodate the brake caliper.

[FallenAngel]

Great! I'll try that. I haven't seen anything in the service manual for rear wheel alignment. Is there adjustment to get it in line with the front wheel if its not right?

The best way is to put the bike on a jig
I know riders that will use A straight edge I know one guy that uses a florescent bulb claiming that it is the best tool for the job
As long as the tires are the same width a straight edge should work
You want the bike as straight and level
set your straight edge on both sides of the rear tire and check the distance of the front tire
If the tires have a different width then scribe a line where the straight edge is on the floor and measure the distance from the tire to the line
Or you can use the butt method
How does it ride does it feel like it wants to turn tighter to one side and does it stop in a straight line when you lock up the rear wheel

Back to the vibration
Also pay particular attention to the splines in the couple that goes into the trans mission for wear
If your bike has been hard tailed for a long period of time(this part was designed to move) you may find excessive wear in this part

[hillsy]

Great! I'll try that. I haven't seen anything in the service manual for rear wheel alignment. Is there adjustment to get it in line with the front wheel if its not right?

There's no way to adjust anything if the wheels are out of alignment on a shaft drive bike - with the exception of slightly moving the swingarm between the frame spars at the pivot. But we are only talking a few mm....and not all shaft drive swingarms are moveable - some have a fixed point on one side and the other side is to adjust bearing tension.

[Designer]

Addressing the appearances that the Wheel/Tire are not centered in the Swingarm,...this is important to keep in mind;

I almost forgot to answer you question about wheel and swingarm alignment. Yes, the wheel is offset to the left but it is in line with the front wheel. Suzuki make the right side of the swingarm wider to accommodate the brake caliper.

I'd first check to see if the Rim appears to be centered over The Hub itself. And,...does the bike Track Straight when riding it, or does it tend to drift ?

There is a small amount of "adjustment" available in that the Wheel can be moved laterally on the Axle with Axle Washers at the joint of the Differential Drive Splines, but it is very small. Could this little bit be the offset you are concerned about?

[Herb]

The thing to check is the wheel alignment between the 2 wheels. If it is correct then the wheels are in alignment and that is what counts.

I went out and checked the wheel on my bike and there is quite a bit of difference of the clearance on each side of the swingarm.

This process takes 2 people but it works. I used it on a bike that had been crashed to make sure that everything was straight.

get 2 really straight boards, I used 2x4s 8ft long. one person holds the bike upright with the front wheel straight. slide the 2 boards on each side of the real wheel, really tight against the tire. measure the distance between each board and the front tire. The distance should be the same. if it is out a little bit redo the boards and verify the front wheel is straight and the bike is straight up and down.

When I did it it was within almost identical and varied slightly depending on how vertical the bike was and straight ahead.