Speaking strictly from my little epxerience with a WONDERFUL MC28, cracks in my hoses that connected to the solenoid were preventing the servo from doing what it should have been doing...or at least sending the correct signal me thinks.

First I would suggest checking/replacing the air hoses and getting them hooked up as normal. (Mine were cracked and letting air in).

I think you may find your servo will (should) work more accurately to start adjusting the RC valves as explained here in the tuning section:

http://www.nsr-world.com/tuning/250-tuning/engine/

Dana
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2016 Husqvarna 701SM
2021 Husqvarna FS450 supermoto
2014 Honda CRF250R supermoto
1995 NSR250r MC28