There is a wholesale exodus of racers away from Showa SSF and Kayaba PSF air forks. How can we tell? Virtually every suspension company is offering conversion kits to turn air forks back into coil-spring forks. What is a little ironic is that KTM’s WP AER air forks have also been caught up in the coil-spring fever. We find this strange, because of all the air forks gracing production motorcycles, the AER air forks are not only the best air forks made, they are the least complicated and simplest to live with. But, once an epidemic starts, no one is immune to the fever.
So it was with some trepidation that we had Factory Connection remove the WP AER air forks from our 2017 Husqvarna TC250 two-stroke and install their new AER spring conversion kit. We planned to race the bike in the Pro class at the 2017 MTA World Two-Stroke Championships and spent considerable time testing settings with Factory Connection before we were convinced that the coil-spring kit offered something better than the plain-wrap AER air forks. Obviously, we were going to gain a couple pounds, but since the Factory Connection kit only uses one fork spring and the Husky TC250 only weighs 211 pounds, it was weight that we could justify—if we got better performance.
Factory Connection’s conversion kit has five optional spring rates—0.88 kg/mm, 0.92 kg/mm, 0.96 kg/mm, 1.0 kg/mm and 1.04 kg/mm. If you own a KTM or Husqvarna two-stroke, you should go lighter on the spring rate than if you own a four-stroke, but as with any fork mod, you will have to have it sprung for your weight, speed and track condition. It should be noted that you can leave the stock WP valving in your forks and just have Factory Connection modify the air leg.
Why only one spring? Since the stock WP AER air forks have the damping in the right leg and the air in the left leg, it is cheaper, lighter and more efficient to just replace the air cartridge with a coil spring, basically mimicking the Showa SFF single-spring fork that comes on the Kawasaki KX250F. It goes without saying, but we will say it anyway, that the single spring is mathematically double the spring rate of a two-spring fork.
What are the tuning possibilities? (1) Clicker settings. (2) Factory Connection re-valve. (3) Optional spring rates. (4) Preload adjustments (the Factory Connection conversion kits come with an external adjuster that allows up to 8mm of preload adjustment). (5) Oil height (changing fork-oil height is a much more effective tuning strategy on a coil-spring fork than on an air fork).
How do they work? As a rule, air forks tend to lose tactile feel with the ground. They lift off over small bumps and are vague across rough ground. Coil-spring forks track more accurately. They are suppler. Coil-spring forks feel more connected to the ground, improve cornering and absorb small square-edge bumps better than air forks. In short, front-end bite is vastly improved.
What does it cost? The conversion kit is $599.90. This price includes installation of the spring, removal of the stock WP air chamber and installation of the hardware to hold the coil spring. There is no machining involved, so the spring kit can be removed and the air cartridge reinstalled later. For more information, contact Factory Connection at (800) 221-7560 or www.factoryconnection.com.