Silly question but can anyone tell me that when reving the motor of a nsr 250 mc 21 will the exhaust valves move?
Yes they should be moved via a cable driven off a servo under the seat, directly related to engine RPM
The servo is under the tank located near the headstock . The valves should move when you blip the throttle . Remove the nuts from the powervalve pulley and see if you can rotate the shaft freely . Then see if the powervalve servo motor can move , if they all move freely you need to check the wiring and see if there is a signal coming from the pgm . Most times the pgm gets cooked inside and needs repair , normally a resistor overheats from strain caused by coked up powervalves .
Have a read of the tuning section on the NSR World site too Brizfox. The power valve setup is pretty crucial with regard to how much grunt your engine will put out. They have a description of what you need to do to adjust the valves for optimum performance. http://nsr-world.com/tuning/250-tuning/engine/ If the valves are coked up as Neal mentions (which is likely as not many get serviced on a regular basis) you will definitely want to get them out of the barrels and give them a clean. Getting them out is not an easy task with normal tools. Tyga sell a handy little tool that doubles as both an RC Valve and Flywheel puller that makes the job much easier and you will be way less likely to damage you barrel. When you clean them don't use anything abrasive. A blunt flat blade screwdriver is handy for removing big buildups but you have to be really careful not to mark the metal. Tyga also sell the seals and circlips. When you remove the seal out before pulling the valve, you will see a circlip on the RC Valve shaft. You don't need to take this off to pull the valve; it's only there to help position the valve. http://tyga-performance.com/site/product_info.php?cPath=71_25&products_id=1339
