I'm familiar with other bikes; I've had 41 so far. I still say the suspension, setup and loading are more likely "primarey" causes than tires or spindly forks but I concur that a number of "weak links" add together to manifest the problem and I agree that I would start on this particular bike by changing the tires and increasing pressure to try to reduce the effect.
FWIW, my standard wobble post:
Way too many people think that addressing the symptoms by dealing with handguards, fenders, fork braces, etc. are the answer rather than dealing with the real issue which is related to suspension setup and loading. I'm not convinced that the KLR is any more susceptible to instability than any other bike with long travel, lightly damped suspension and the Owner's have a propensity for severe and uneven loading.
There are some problems that need to be checked;
- bad/lose head bearings
- condition of wheel bearings and suspension bushings
- wheel and tire condition and appropriate tire pressures.
.....beyond that, It's settings;
- proper sag settings and adequate damping
- proper bike loading
- avoiding inappropriately un-aerodynamic loads
addressing the symptoms rather than the cause can help but IMO shouldn't be done until all the aforementioned items are checked and corrected if necessary. Nonetheless these can help stability;
- fork brace
- smaller fender or lowered fender (I use a polisport as I hate both the supermoto and low mounted fenders)
- consider tank bags instead of putting everything in huge panniers which affects both weight loading and aerodynamics.
My 2001 had some high speed issues that went away as soon as the sag was set properly....and after my Cogent suspension was installed, both my KLR's have been rock steady.....even with full knobbies and low tire pressures (20 - 22PSI). Lastly, as others have mentioned, the rider also plays a part; keep a relaxed light grip on the bars and don't tighten up. Changing your position (move forward/lean forward) can help too.
Lots of things come into play, but I believe, as apparently does pdwestman, that tire pressure is a key factor and everything Iíve ever read on the subject agrees with that, assuming that there is no other play in the system from worn wheel bearings or steering head bearings.
Loading of the bike is a secondary factor.
Suspension setup is a tertiary factor.
So, if you have a high speed wobble, I would troubleshoot in this order:
1. Play in the steering/frame (front wheel bearings, steering head bearings, loose spokes, etc.)
2. Front tire pressure and sidewall stiffness (need to have the right tires)
3. Vehicle load and load distribution
4. Suspension if all else fails, but this is very unlikely to be a contributing factor to high speed wobble unless something is grossly out of whack.
Lack of stiffness in the front frame and forks is a huge issue, but not one that we owners can generally address in any meaningful way. A KLR is simply flexible and this is the nature of the beast.