isn't bouncing a shock rebound issue?...of course if the springs are too soft for the rider's weight, it'll need stiffer springs to rebound properly...for my weight of 150 lbs. +/-, the klx250sf springs were fine and the shop just had to adjust the rebound on the front forks to get rid of the bouncing and they adjusted my tire pressure..they thought it was inflated little on the high side...mainly, i was happy that the adjustments eliminated my high speed freeway wiggles...

 

Interesting, I myself only weigh about 135, not sure if the springs are just worn from all the wheelies, you think that the stock 29 psi for the front tire is good for a dual purpose tire? I think I am running about 25psi in the front and 30 in the rear. I will try adjusting the pressures to see if that makes any difference.

 

Agreed, a bounce is most definitely a balance issue based on the fact that there is a specific zone when the harmonics would cause it. Unlike a wobble or a weave which go side to side.

If it's not been said, if you let the air out of the suspect wheel (undo any rim lock) and rotate the tire on the rim 180 degrees you may reduce or eliminate the ations. Otherwise take off the wheel and at least do a static balance. Some bike shop can probably do a spin balance for a few bucks.

If it was the suspension it would be due to damping - or lack there of - aka the seal let all the fluid leak out of the fork legs. That would be no damping, but it would happen at about any speed and only after hitting some bump of some sort..

Soft springs won't likely do it, at least it never did on my trials bike, which has seriously soft springs due to the intended style of riding. but I also did fast trails and road riding with it too... never had a bounce.

Of course this is my semi-educated guesstimation without seeing or riding the bike.

 

Yup, according to the OP's description of the problem, and unless all that wheelieing has broken a spring or bent the front wheel, an imbalanced front tire needs to be ruled out first. Otherwise, all other remedies involving springs, damping, and tire pressures, are just band-aids to the most likely problem...

 

One other possibility, but not likely, because you'd feel it all the time - tire not quite popped up on bead.

I'd still double check the balance - it's free to do and little cost to correct, then while doing it you can also see if bearings are hosed.

Geez, another thought - is the front tire extremely worn? You know, the tread blocks cupped quite a bit. That will show up most at the speed range you mention. If the tire is fairly worn, a new one might just solve your problem. I had a street tire do that on my Zephyr 550. I have the bike raised in the rear about 2" and the front tire is one profile lower, to quicken the steering. That also emphasizes it when the tire is worn (cupped) and wants to oscillate. The tire looked good if you didn't know what you were looking for. Lots of tread, but a very noticable lip on the trailing edge of the tread due to wear. that lip on the tread sets up the oscillation or wobble. Lots of people experience it when coasting down through the 30-45 mph range hands off the bars. It can develop within a few thousand miles. The more the cup the quicker the wobble amplifies.

 

New tires that I put on barely even have 200 miles on them. I did do a static balance on them, the only thing was the front tire needed 1.25 oz of weight which a co-worker told me was a lot. The front tire is barely even worn, it still has a lot of the little rubber pieces that come on new tires. The tires are fully seated on the rim. When static balancing the rim, it showed the valve stem as the heavy spot. There is definitely no sign of forks leaking, the rim is straight.When I get some free time I am going to bring the tire to this bike shop that I know and see if they will spin balance it for me and see how it looks. Thanks for the input guys.