Whoa boy.....this will make the tire and oil threads look tame.
There are many, many riders, including yours truly, that run positive air pressure in the forks of their Gen I KLR 650's. I have been running about 8 lbs of air in my forks for over 35,000 miles. One KLR 650 that I am more than a little familiar with runs 20 lbs of air in the forks continuously. My experience with air in Kawasaki forks predates my involvement with the KLR 650. I put about 90,000 miles on a Kawasaki Concours that had the same design fork system. The front suspension was "tuned" with, you guessed it, air. About the same amount I use in the KLR 650. One of the most noticeable advantages was the reduced amount of fork dive one experiences when braking. About 60% of the fork dive went away.
Now while some of the loyal run and get a rope to hang me with [Heresy], take a moment to read the spec sheet on a pre-08 [read, GEN I] KLR 650:
Engine: Four-stroke, DOHC, four-valve single
Bore x stroke: 100.0 x 83.0mm
Compression ratio: 9.5:1
Carburetion: Keihin CVK40
Ignition: Electronic CDI
Final drive: Chain
Frame: Semi-double cradle, high-tensile steel
Rake / trail: 28 degrees / 4.4 in.
Front suspension / wheel travel: 38mm leading axle, air-adjustable preload / 9.1 in.
Rear suspension / wheel travel: UNI-TRAK single-shock system with 5-way preload and 4-way rebound damping / 9.1 in.
Front tire: 90/90x21
Rear tire: 130/80x17
Front brake / rear brake: Hydraulic disc / Disc
Overall length: 86.8 in.
Overall width: 37.0 in.
Overall height: 53.0 in.
Ground clearance: 9.4 in.
Seat height: 35.0 in.
Dry weight: 337 lbs.
Fuel capacity: 6.1 gal.
Wheelbase: 58.9 in.
Air. Adjustable. Preload.
I know it doesn't specifically mention the forks, but in this application, the front suspension / wheel travel all takes place within the front fork system.
This not a new topic or a topic limited to KLR 650's. I have been to motorcycle rally's in the 1980's where the only reported disturbances were knife fights among the Gold Wing crowd about air pressure amounts in their front fork system. Kawasaki Venture forums consulted Dr. Jack Kevorkian to form methods of dealing with the naysayers regarding high air pressures in Kawasaki forks.
If you don't want to air them up and you like running them with zero preload with the excessive dive and bottoming out thats fine, but don't spread disinformation about it ruining the seals which it will not do. The seals get ruined from dirt, dry rot, and mechanical damage. Take them apart, tell me how the pressure is going to ruin your seals. I beg anyone to show me a set of OEM seals blown from applying air to the forks, that would not of blown anyway. Matter of fact, I'm not sure that I have ever laid eyes on a set of factory fork seals blown on a KLR 650. Leak, yes. From dirt, not air pressure. A little air pressure, I think, will resist dirt from working into the seals. So there.
Wanna know where the biggest positive effect came for me? The bike lost the front end dive I was getting when upshifting. I had a slight fork dive that was enough to require compensation by the rider [me]. That little bit of improved stability had a tremendous improvement in my performance, especially on gravel and dirt.
Coming up in October, I'll run in the AMA KTM Shenendoah 500 Dual Sport Series. I'll up my fork pressure to 20 lbs to maintain a better ground contact consistency. The trade off will be a bit rougher ride. But with better front tire ground contact, I can maintain higher speeds. It also greatly effects the decision to up or down shift, as the action will have little if no effect on the bike's suspension. In anything rougher than the dual sport rides, air in the forks becomes counter productive, as a suspension that offers less resistance takes up the impacts of rougher ground.
While all this seems antagonistic, [and it may be], I'm also a realist. I know this all would be much more palatable from a reliable source like Myth Busters.
I approached this Myth Buster to deliver ya' all this info. Apparently there was some misunderstanding in what I was asking. Who woulda thunk a few questions about forking would get you a restraining order thing.