400EX Decompression Mechanism

[rYan01400EX]

On my 400EX, the crank was spun the wrong way messing up the decompression mechanism... Causing me not to be able to adjust valves correctly... how do I solve this problem?

[GPracer2500]

Just spin the engine around the correct direction a couple of times (counterclockwise when facing the left side of the engine). The auto decomp should "reset".

The auto decomp mechanism has an "reverse decomp" function as well as the normal decomp function. It's a vestigial function that's leftover from when the TRX400EX engine was kickstart only in the XR400R dirt bike. It keeps the engine from firing but not passing through TDC and "kicking back" through the kickstarter. You could seriously hurt your leg/foot if that happened.

AFAIK, the auto decomp mech can't be damaged by rotating the engine backwards. It will just hold one of the exhuast valves open until the engine is spun around the correct direction.

[rYan01400EX]

GPRacer,

Man, Thanks alot!