High speed weave.

Getting a bad high speed weave that I just can;t get rid of.

Starts at 110mph and builds in intensity up to 130mph where it gets so bad that I chicken out. Definitely a back of the bike thing. The handlebars stay straight, the back of the bike just feels like it moves from side to side. People following me can easily see it. No change of body position helps. Low freqency, not a wobble or handlebar shake thing.

ONLY happens when HARD on the power. As soon as you lift, she's a straight shooter.

Here's what I've done to try and stop this:

Center rear wheel to be inline with front wheel.
New wheel bearings.
New swingarm bearings.
Braced stock length swingarm.
Ohlins rear shocks.
Fork brace.
Taper steering head bearings.
New tires (Avon Roadrider).
Steering damper (no effect!)
Bigger balls (only works until I remember I would like to live to use them)

Any theories?

-Dave

have you checked for cracked welds on frame?

I think thats MawKaws built in "Your balls have just outdriven your brains indicator." If u r serious that u are driving an old machine like these at sustained speeds over 110 mph,please take some advice from an old fart and slow down and enjoy the rest of your life.bj

Frame is in good shape. No cracks or even flaking paint which would indicate an impending crack.

I don't usually travel at sustained speeds over 100. I just need to get this wobble nailed down so I don't go flying off my bike at the end of the dragstrip.

-Dave

rear wheel straight/tight in swingarm?
checked rear tire and wheel,no slipped belts in tire?
rear tire balanced?
have you tried jacking up rear of bike and shaking wheel/cush drive?

kind of hard to do long distance autopsy over the computer! :laugh:

I would check the runout of the wheel and the tire on the wheel to make sure both are dead true. Assuming the wheel is true and the tire is true on the wheel, the only other thing I can think of that you haven't covered is the chain/sprockets. If you check the chain tension while you turn the rear wheel does the top length of chain get tight and loose as if a section of it is worn more than another section? I don't know if this could cause the weave, but if the tension between the countersprocket and rear sprocket varies, it might be pulling and relaxing the pull on the rear sprocket/axle causing the swingarm to flex a tiny bit. Just a guess; no personal experience with this problem. Ed

the bikes get lighter in a straight high speed rip...they "stand up"....fairings and such work to give downforce on modern bikes some...but an unfaired big four once above 100 is skiping along on smaller and smaller contact patches,as these big bikes tippy toe along at 100-110-120-125---they encounter pavemant diferences and need to send these down the line and re-set...it all needs to happen in cycles and fast too......which imo magnifies any alingmnet or balancing or tire issues...like many have stabbed at ..i think something in one or both wheels is rotating in a separate way form the other wheel or rest of the bikes center lines...

650ed wrote:

I would check the runout of the wheel and the tire on the wheel to make sure both are dead true. Assuming the wheel is true and the tire is true on the wheel, the only other thing I can think of that you haven't covered is the chain/sprockets. If you check the chain tension while you turn the rear wheel does the top length of chain get tight and loose as if a section of it is worn more than another section? I don't know if this could cause the weave, but if the tension between the countersprocket and rear sprocket varies, it might be pulling and relaxing the pull on the rear sprocket/axle causing the swingarm to flex a tiny bit. Just a guess; no personal experience with this problem. Ed

Good theory...

Maybe she just doesnt like it. Mine starts to feel squirly at 110-115mph, and I don't particularly need to be going that fast on a relic of a bike anyways.

Course, I live in Canada, where all the drivers are nutso $#&@s anyways!

:laugh:

Fug* dude, I generally just assume that motorized vehicles get weird past the ton.

beefsquasher wrote:

...Center rear wheel to be inline with front wheel....

Should center rear wheel by assuring equal distance on both sides between centerline of swingarm pivot bolt and centerline of rear axle.

Chain should be viewed in straight line and with no jog as it leaves rear sprocket and mounts c/s sprockot.

Tire track lines should be parallel, but not necessarily travel the exact same line.

Good Fortune!

One other thing to confirm....

Had similar with my ZX636 front end... Only above 85mph did I notice.... Turned out the rotors where warped...
Would drag the pads a tad on the warp thus causing the wobble effect...

Raise the front end...
While observing over head, spin the front tire looking at rotors(s is dualies)...

I replaced rotors, 110mph no issues to date other then crapping my pants....:blush:

I think 650ed is spot on: Wheel trueness; tire roundness; variation in chain length; true running sprockets. I am a big believer in tire balance as well.

I have also experienced a tire that was very round, and in good static balance, but caused a 40 MPH wobble due to being hard and soft or perhaps thick and thin in places as you go around the circumference. Poorly manufactured.

One more thing. The bad tire was on the rear of my bike, but caused the front and handlebars to wobble. So check your front tire and wheel also.

New tires changed my bike from semi-scary to velvety smooth with great traction. Extremely pleasant and confidence inspiring.