M7 power valves

Carb cleaner, brush and lots of elbow grease. Clean one at a time so you don't have to ask which side is top.

Check your valves are even in the right way(beveled side down towards the Y pipe), and if both cables are hooked up and measured the right length. I recommend using a razor blade and brake cleaner.

What happened on my firecat, was one of the valves was sticky with carbon and oil. And was slow to snap back down, so when the servo spun back down, the cable wiggled its way off. And every time i would crack it, the sled would sound like it was gargling water. For my servo there was an updated clip that snapped over the servo to keep the cables in the servo even if a valve did stick.

I agree use carb cleaner and do one at a time so you know which way to put them back in (saying from my own experiences)

If it's missing on the top end it's probably the STATOR, usually power valve sticking will cause power loss but still run smooth.