Saturday, August 16, 2014

Tecumseh TVS90 Governor -- Static, Baseline Adjustment

There are several adjustments associated with the TVS90's mechanical governor. There is one primary, fundamental adjustment that establishes the relationship between the governor's 'at-rest' control lever position, and the carburetor's wide open throttle (WOT) position. The adjustment is 'static' because it's made with the engine stopped; it's 'baseline' because it's the initial adjustment from which correct governor operation can commence and be further adjusted.

One simple fact about the governor's operation will help you understand the adjustment; i.e. an engine stopped condition must result in a WOT condition. Think of it this way -- the governor must respond to a slowing engine by opening the throttle to speed up the engine. There's no slower engine speed than 'stopped', so the appropriate governor response to that is WOT. (Even though a stopped engine cannot, of course, accelerate.)

Here's a view of the governor's control arm in its at-rest (engine stopped) position.

(The shroud, air cleaner and fuel supply hose have been removed for clarity. I've whitened the end of the governor's control shaft.)

The governor's control shaft swings the control arm via a short, rectangular clamp-arm. A 1/4" hex head screw on the clamp-arm permits adjustment of the control arm's angular relationship to the governor's shaft. Here's the adjustment procedure.

a) Throttle control cable disconnected. Clamp-arm loosened.

b) Clamp-arm/governor-shaft biased fully CCW. (i.e. the governor is held at its at-rest position.)

c) Throttle held at WOT.

d) Tighten clamp-arm.

That's it; the adjustment is made. The governor's at-rest (engine stopped) condition produces a WOT condition. The governor is ready to operate with the engine running. Governed operating speed and governed idle speed can be adjusted.

# # #

# # #