[866]

Have your steering head bearings checked. At least on the Concours, big K is semi-famous for not tightening them adequately during assembly and is seems as if no mechanic doing the final setup ever does.



Usually, you'll find that they need about 1/8 - 1/2 turn to be tight enough. As on bicycles, "tight enough" is a delicate balance between too tight, making it difficult for the bike to turn and not tight enough, causing wobble.



One other fix is like the one the doctor recommended to the man who said, "Doctor, whenever I raise my hand this high, my shoulder hurts. What can I do about it."



The doctor replied, "Don't raise your hand that high."



Phil Tarman

 

[38500]

I assume you checked all the obvious (forks straight, front tire not cupped, etc.). One thing that is often overlooked is that if the rear wheel is not aligned, it can create steering problems, including wobble (also, if the swingarm bearings are worn). Check to see that it is aligned properly: sometimes when you take the wheel off, or when you tighten the chain, the wheel can be crooked (front to back). There are simple ways to check what happened, one involving a string. If everything checks, I am with the first poster: don't raise your hands.....

 

[57343]

I had a similar problem on my 1982 Yamaha Seca 650. Basically the same problem as yours, but on and off at different speeds. A weight had fallen off of my front tire. Check your front tire balance. If that's it, it will be a real easy fix.

 

[14173]

Another often overlooked item is LOOSE SPOKES. My wife & I nearly bought it on Grandfather Mountain due to loose spokes. Started as a slight wiggle, eventually, EVERY spoke in the rear wheel was loosened! If cast wheels, see above - steering head / wheel alignment.

 

[43093]

I just add one thing. Front tires are more susceptible to cupping when proper tire pressure is not maintained. Some brand tires are worse about it than others.

 

[37372]

One more thing - a squared-off rear tire could also be the cause.

 

[3810]

Many bikes that have never been dropped have a wobble in the 45 MPH range when you let go of the bars. It is due to chassis dynamics and/or tire construction. It usually has no other adverse handling problems. The solution is don't let go of the bars. Since your bike has been dropped, it might be worth your while to have the frame alignment checked with a Compu-Track. Hope this helps. Cheers, Jack

 

[3810]

Loose spokes on a Ninja 250 would be a REAL problem!

 

[eojmo]

This is a fairly common occurance,usualy the front tyre.Check the obvious,pressure,wheel balance,flat spots from heavy braking etc.Depending on how old your tyre is,they can wear down more on one side because of road camber and heavy cornering.Also the tyre brands can make a differance.I once maintained a fleet of cop bikes and one particular brand made the bikes shake there heads at low speed but they where ok at high speed.The balance was good ,pressures spot on etc,but the only cure was to change brand and the problem was solved.

Make sure you check wheel bearing play, plus steering head tensions before getting too involved in expensive repairs.

 

[rapier]

If nothing is bent check the stem head bearings. In most cases this comes from misalignment and tension between the two forks.



Put a jack under the bike and just get the front wheel up. Losen all the bolts from the axle thru the fork clamps. Since your at it check what height the fork measurement above the top triple clamp is supposed to be and put them there. Kick the front tire a few times. Snug the axle bolt. Kick again. Snug the top fork clamp bolts, let down the jack, use the brake and pushdown on the bars to compress the forks.



Or some combination of this the idea being to get the assembly all in line. final tighten from bottom to top. If the tire is badly scalloped you might not end the problem totally. A new tire will be needed then.



Also a badly balanced tire can contribute. A flawed out of round tire will too.

 

[rapier]

Oh, dont take your hands off the bars unless your 1000% confident it's as stable as train. You shouldn't anyway of course.



This problem is almost always at it worst on decel from engine braking, which is of course what you do when you take your hands off the bars.

 

[57152]

Thanks, for the advice- I assure you, my hands are very very close to the bars when I do this. I have wondered about the effect of deceleration due to engine braking.

Thanks again,

Matt

 

[32324]

My '86 and '87 GSXR750s did this. It has nothing to do with a bent frame - it's just inherent in the design/tire. You should probably check the head bearings - but usually they just make the bike feel sluggish at parking lot speed. If you're worried about frame alignment, just have somebody follow you and see if your wheels are running in the same track. If he can't see a difference, it's not enough to create a problem. If you don't believe me, just deliberately misalign your rear wheel via the chain adjusters and try it. You'll find it doesn't affect wobble. So I'd just not worry about it. What I do is not take my hands off the bars.

 

[52321]

Try using your hands.

 

[49596]

The only time my 87' GSXR750 had a "front end wobble" was after I replaced the rear tire with a wider one. Once back to the 140/70 original tire size there was no problem, so I’m not so sure about the "inherent design" thing.

 

[pplassm]

Really. IIRC, this is common on older design bikes, like your GPZ250. Newer bikes with modern tires don't seem to exibit this same behavior.

 

[33129]

This has almost always been the trouble when my bikes started to wobble. And once cupped, they only get worse, even with proper inflation.

 

[57343]

Like I said, I ride a 1982 Yamaha, and had the EXACT same problem. I looked at the wheel, and there was a clean spot where a tire weight had been. Replaced it, and now I can ride for miles with no hands. Not that I've tried, but I'm sure I could.