The valve cover (official reference Rotax : 251252) Fills several crucial technical roles:

1. Superior Expansion Chamber: It creates the space required for vertical displacement of the piston and the membrane. Once screwed on the valve body, it tightly closes the system to allow the pneumatic pressure to act.

2. Setting support: The top of the hood is threaded to accommodate the screw or adjustment wheel. It is by taking on this cover that you compress the support spring to adjust the triggering of the valve.

3. Mechanical protection: It isolates the precision mechanism of external projections (dust, tire gum, water splashes) and potential shocks during mechanical manipulations.

4. High performance material: Designed in a reinforced technical polymer, it is studied not to deform under the effect of the radiant heat of the exhaust.

💡 Michel's trick

"Attention to the tightening! The hood attaches with two screws on the valve body. Do not tighten as a deaf: if you will deform the hood's base, you will create a micro-air leak and your valve will never go upstairs. My advice: Check also that the thread on the top is not messed up. If the adjustment wheel moves alone with the vibrations, your engine will be unstable!"

🎓 Tuto: assembly and verification

1. Positioning: Before setting the hood, make sure the spring and piston are centrally centered. The hood must naturally down until the body's contact.

2. Uniform tightening: Screw the two mounting screws alternately to crush the membrane symmetrically.

3. Sealing test: Once the hood is mounted, screw the adjustment knob. If you hear an air whistling by manually pumping on the valve, the hood is misplaced or the seal is pinched.

4. Cleaning: When disassembling, clean the inside of the cover to remove the traces of oily condensation. A clean interior guarantees that the piston slides without any friction.