Searching is caused by several things, lean mixture is one easy one
(look at the base of the insulator on the plug -- should be tan to
dark tan), but a fouled plug, air leaks, plugged air filter, worn
linkages, etc will also cause trouble.
Verify that the governor linkage is free -- if you move the air driven
flap, it MUST spring back smoothly and immediately. All the links,
hooks, and springs in the linkage between throttle valve and air flat
(or centrifugal spring on newer engines) must be clean and swivel
freely.
If the linkage binds anywhere, the engine will continue to speed up
until the linkage moves, which will be too far, and the throttle will
close too far, the engine will slow down too much, then surge up too
fast when the linkage finally moves again. Grass, crud, oil residue
and dust, etc will all cause trouble.
So will running too rich, as the power output is way down. A stuck
float can make it run funny too.
And don't neglect the possibility that the shut-off wire insulation
has rubbed off somewhere, causing the ignition to cut in and out! Had
this on the Snapper self-propel I bought this spring for $100, had
been set very rich to compensate for the "poor running" due to the
shut-off wire coming adrift and intermittantly shorting out. PO said
it bogged down in heavy grass, which it did. Also burned lots of oil
and smoked black once in a while, and stank of unburned fuel.
I go the wire to quit shorting by removing it (have to take the cowl
off soon and fix the recoil spring anyway, will get it in place then)
and leaned it out a bit -- runs like a champ, doesn't burn oil
anymore, and uses much less fuel. Still surges a bit on startup, but
I suspect that's a carbon/oil ash fouled plug which I will replace soon.
I would not run one without a governor, the blade is never balanced
well enough and a flat-head single cylinder engine will turn WAY too
fast to stay together without a governor!
Peter
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