Cold start advance - how does it "turn off" over 2

[rallydiesel]

How does the timing advance retard itself over ~2000 rpm? I assume the roller carrier starts to rotate and retard when the rpms reach 2000. I just wonder how it actually does this. I know the advance pin sits in the piston that is under tension by a spring. How does the input shaft's rotation transfer over to the roller carrier? I thought they were separate units?

Thanks for any replies.

[QuickTD]

The cold start isn't really "disabled" above 2000rpm, the hydraulic advance just takes it past (more advanced) than the mechanical cold advance position beyond 2000rpm.

 The input shaft doesn't directly drive the roller carrier, it is driven by hydraulic pressure on the end of the advance piston. The hydraulic pressure is provided by the transfer pump and increases with engine speed, advancing the timing in proportion to engine rpm.

[rallydiesel]

Ahh, ok. Thanks.