"cnctut" bravely wrote to "All" (11 May 05 10:52:14)
--- on the heady topic of " Lawnmower idle question"

From the small motor faq:

" Air vane governor. The air flow provided by the
flywheel/blower passes by a plate which is coupled to the
carburetor throttle plate acting against a spring force.

Flyweight governor. A spinning gear assembly with a pair of
weights is driven by the camshaft. As the centrifugal force
of the weights increases, they move a sleeve which presses
against a lever whose shaft passes through the crankcase.
This lever then operates the carburetor throttle plate
against a spring force.
With both types, increasing the spring force will increase the
engine speed.
"

Hunting is often caused by a defect in the governor system. Check the
blade (plastic?) of the governor paddle is free to move and that the
cam to which it connects has the proper spring tension. As the motor
speeds up the flywheel impellor blows air against the blade and cuts
the trottle down. When the motor slows down the blade drops back and
the spring returns the throttle higher.

Often grass goop gets into the governor paddle axle and may stick or
seize. You might need to remove the pull cord/motor cover and perhaps
the carb/fuel-tank to get at it. Thankfully you won't need a puller to
get the flywheel off. If you ever do, inspect the key pin in the
shaft, as it must be snug, not worn. This could also cause hunting.

OTOH, if instead of the fan your motor has a governor linkage coming
out the bottom of the motor, then the linkage may have slipped.
Hunting means in this case it may be opening the throttle too much.
There is also a spring arrangement in this type to the trottle cam.

A*s*i*m*o*v


cn From: "cnctut"
cn Xref: aeinews sci.electronics.repair:47853

cn spongehead wrote:
I have an old Briggs and Stratton 3.5hp push behind lawnmower and the
idle revvs up and down constantly. Never idles normal. The spring
on
the shaft idle looks good. Any help on what this might be would be
greatly appreciated.


cn Spongehead--

cn Recommend cleaning the air intake sponge first then let us know if the
cn problem still exists. I assume you have the 99 dollar Walmart mower
cn with no variable throttle.

cn Tut


.... The first rule of intelligent tinkering is to save all the parts.