I have a 2002 Honda CR250. It is great shape, but I think that I need to adjust the power valve. I don't have a clue on how to do it. Can MXA help me?
When Honda dumped their centrifugal power valve system
for an electronic one, you could hear the whispered doubts float
throughout the motocross industry. Electronic power valves were nothing
new. Almost every manufacturer had tested with them, some even
raced the GPs with electric power and every one, save for Honda, shelved
them. What were the problems? Turbo lag (at least an electric version
of it), servo motor quality, price and computer control systems.
Honda felt that they had a handle on the problems. But,
there is one area where Honda had no control over—owner maintenance. Since
the servo motor is connected to the power valve via cables, and the
cables tend to degrade over time, the performance of the CR250's
electronic power valve depends on cable tension.
The CR's power valve servo has no way to take up slack in the cables.
The power valve's electronic module pulls the same amount of cable
whether the cables are properly tightened or lazily slack. If the cables
are slack, the servo motor will spend some of its precious rotation
removing slack—which means that at the end of its travel, the flapper
valve will not have moved all the way up in the exhaust port. Oops! If
the power valve cable is loose, a savvy rider will notice a loss in
top-end power. As with any cable-driven system, the cables must be
checked and tightened at regular intervals. If you haven't checked your
cables, you should. Unfortunately, many CR250s came from the factory with loose power valve cables.
HOW TO FIX IT AT HOME
Luckily, adjusting the CR250's servo cables is not much more complicated
than adjusting a clutch cable. Here are the five steps to getting your
flapper valve to open all the way.
Step one: Pull off the RC valve cover and turn the actuator counter-clockwise until it stops.
Step two: Push the left-side cable to the left. If you can push it to the point
where it touches or almost touches the cylinder, it is too loose.
Step three: If the cable is loose, you will have to push the rubber cover on the
cables out of the way to get a 10mm open-end wrench on the lock nut.
Step four: Using an 8mm opened-end wrench adjust the left side cable until it has a tiny bit of play in it. Do not make it taut.
Step five: Tighten the nut, pull the rubber cover down and put the RC valve cover
back on. Now, enjoy the benefits of a fully open exhaust port.