MXA TEAM TESTED: RIDE JBI KTM BLADDER FORK PRO PERCH
WHAT IS IT? The Ride JBI Pro Perch is a fully modified, high-performance spring seat that replaces the one-dimensional WP twin-chamber design on the WP bladder fork (not the newer-model 4CS fork).
WHAT’S IT COST? $350.00.
CONTACT? www.ridejbi.com or (480) 269-5585.
WHAT STANDS OUT? Here’s a list of things that stand out with the Ride JBI Pro Perch KTM twin-chamber fork modification.
(1) History. MXA first tested the JBI Pro Perch on the Showa-equipped 2014 Honda CRF250. It was a hit among test riders because the spring seat, which they call the Pro Perch, firmed up the initial part of the stroke while providing excellent bottoming resistance. Although KTM upgraded to WP’s 4CS technology for 2015, we are well aware that there are still thousands of older-model KTMs circling the track. Additionally, the European-spec KTM motocross bikes didn’t receive the 4CS fork for 2015. Thus, the Ride JBI Pro Perch KTM twin-chamber fork modification is applicable to our friends across the pond, as well as racers who own older KTMs.
(2) Ingenuity. The objective of a fork spring seat is to flow oil at a specific rate through the system. The rate at which the oil flows depends on the spring seat’s orifice sizes. KTM’s WP twin-chamber spring seat has large ports to flow a considerable amount of oil for excellent bottoming resistance; however, the large ports deliver harshness at the beginning of the fork’s stroke. As you would expect, a fixed port shape only performs optimally at one fork pressure. The Pro Perch, unlike a conventional spring seat, has a variable port area. There are four shims in the spring seat that open and close based on oil pressure caused by fork compression. They mimic a reed valve. At low speed, the shims open slowly for a plush feel, while a heavy impact causes the oil to force the shims to open wider for better bottoming resistance.
(3) Installation. It is possible to install the Pro Perch by yourself if you are competent at changing fork seals. Ride JBI’s website has detailed instructions and photos; however, if you doubt your mechanical skill, have a professional do it for you. As for the shims, they should not be adjusted under any circumstances. If you have issues, Ride JBI can customize the spring perch shims to your liking.
(4) Setup. Fork setup is still vital in maximizing the performance of the Pro Perch. Lighter riders preferred 60cc less oil in each fork leg, because the Pro Perch metered oil flow via the variable port area on small impacts and ramped up significantly at high speed for excellent bottoming resistance. We believe that fork-oil height is the biggest factor in getting the most out of the Pro Perch.
(5) Performance. MXA harped on KTM for years about the harshness of the WP bladder fork. We always lowered the oil height to lessen mid-stroke harshness, which sacrificed some bottoming resistance. The Ride JBI Pro Perch solved our problems. It drastically improved the suppleness at the top of the stroke while smoothing out the mid-stroke to the point where it didn’t ramp up so quickly. As a result, we were able to run much softer compression settings than normal, and the clickers made a more noticeable difference.
WHAT’S THE SQUAWK? Installation of the Ride JBI Pro Perch requires a modicum of mechanical acumen.