Head shake?

[Bodge]

On my 96cr250 i get headshake when i let off the gas. What causes this? Also could bad steering head bearings(like bars have resistance when turning) cause this? The forks are stock. I want to re build them. I have a service manual on the way so im good in that aspect. My question is what will i be looking for the replace? If they are stock i know i need to put new oil in, but what else? Also should i be able to tell a difference w/ freshly rebuilt forks compaired to the old stockers?

 

[Robcolo]

When you "let off" of the gas, the front end "dives" a bit as weight is transfered forwards. This increases both the effective steering angle and the "Bite" or traction of the front tire. Any irregularity in the tire's path can cause it to steer slightly to one side. This starts a vicious cycle -- as you attempt to correct, there is windup or flex in the forks and with the increased leverage it becomes unmanageable. The usual fix is to slow down the steering by lowering the fork tubes [downwards] through the T clamps and / or lowering the rear end by increasing sag. Did the bike do this when new [my KX did]. If it's something that's just started, then the springs have probably sacked and should be re-stretched, replaced or maybe just need a bit more preload. If you're a heavier rider it's possible a stiffer spring is needed. A bit more low speed compression -either clickers or a revalve - should also help keep the front riding higher during deceleration.

 

[tentbound]

Try a Scotts or GPR steering damper. You won't have any head shake with one of those. If you don't want a damper, then try making sure the shock sag is correct.

 

[DKT735]

A. Change fork oil. This will make a big difference. Make sure there is no pent up air trapped in your forks before each time you ride.

b. Measure your rear end sag and set it to 3.75 or 4 inches. See if it gets better or worse as you increase or decrese sag.

C. How do your forks feel? Increase compression damping and see if it gets better or worse.

d. Increase shock rebound damping and see if it gets better or worse.

Only do B, C and D one at a time. This stuff takes time.