Fast idle wax unit operation.

[Kawasaki Jimbo]

I think I might have asked this question before, possibly on the old MCN forum, but I've forgotten the answer. How does a wax idle valve work? Some sort of collection of piston, spring and a wax-filled cell which becomes liquid as the coolant warms up, but I can't envisage how it goes in and out.

The reason I ask is because the '03 R1 does this thing when it's chilly where it starts (first time) on a low but steady idle and then after one minute the revs rise until it reaches temperature, when the revs settle down again. Why doesn't it go straight to warm-up revs?

The bike also has a flat spot in the first millimetre of throttle movement which actually drops the revs momentarily.

Nothing wrong with the bike, I'm just curious about what's going on and how a relatively crude idle valve can have three stages of warm up.

[Nobby the Bastard]

Wax expands as it warms up and becomes liquid (water is a rare exxception 8ndoing the opposite).

This pushes a piston which in turn adjusts the fuelling via levers.
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[WD Forte]

fermo espanshun innit?

Just like a thermostat in the cooling system or shower valve
in the shower

Wax heats up and expands against a weak spring and pushes a valve open or shut
or maybe does something a bit more complex like lining up/closing
previously obscured/open ports to meter fuel whilst
possibly nudging a throttle's tickover position
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bikers smell of wee

[Kawasaki Jimbo]

Aha! I was thinking of it the wrong way round, where the melting wax allowed a sprung piston to penetrate, but then I couldn't see how it would go back to the cold starting position later.

[Easy-X]

Regarding the flat spot... I'm assuming it's a standard two-cable push-pull throttle. I'd double check you have a tiny bit of slack in both cables. Is it the first iteration of EFI on that year of the R1?
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[Kawasaki Jimbo]

[chris-red]

My TDM has a similar unit and they are known for an issue where they stick. It's not the sealed wax unit it's the piston that pushes against the throttle, it gets stuck in the housing. From factory there is no lube in it. stripping it down and greasing it fixes the issue more or less permanently.
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