Continuing with this (sort of), I have an intermittent problem where despite starting first time, the engine is utterly gutless for a few minutes. It's clear the mixture is off (lean) when this happens.
I know exactly what the issue is, but I don't know why, or how to stop it.
I have narrowed it down to the warmup regulator (control pressure regulator). I have set this exactly right so that it's around 0.5-1 bar when cold, and 3.5 bar when hot. This is the spec both in the K-Jet manual and the 240 Haynes.
However, at the times when it's misbehaving I can see from fitting a gauge that the cold control pressure rockets to 5 bar (super lean) and doesn't move. It's almost as if the WUR is blocked. It isn't though, as I can get flow through the return quite easily.
I can fix it easily by giving the WUR a smack on the body with a hammer. This seems to reset it back to the 0.5 / 3.5 bar setting, and then it runs fine again for a couple of weeks.
So, somehow my WUR is drifting out of alignment and sticking in the fully closed position. I have no idea what could cause this, or why a shock from a hammer would fix it?
Everything inside the WUR has been cleaned up and looks great.
Does the metal diaphragm stick in one position when it's worn? Is there something else that sticks?
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