Small Engines (Lawn Mowers, etc.): Craftsman mower idles very bad???, throttle linkage, low speed

Question
Hi Michael,

I have a Craftsman 5.5 hp mower that was given to me because the previous owner couldn't get it to run. Basically the engine revs up and down on its own. If you pull the primer bulb off and cover the hole with your finger in idles fine. I cleaned the carb, replaced the primer bulb, air cleaner, and spark plug. The only adjustments I see are two set screws that limit the high and low idle. I am at a loss. Any suggestions you could offer would be greatly appreciated.

Thanks,
Jason


Answer
Hi Jason,

First, adjust the two carb mixture screws.  The large high speed screw [if equipped] should start out at 1 & 1/2 turns out.  The small low speed screw at 3/4 turn out.  A third screw, the idle speed screw, similar in size to the low speed mixture, is set to give a good idle speed.

Next, I would suspect a weak or defective governor spring.  It connects the throttle linkage with the governor linkage.  Try replacing it with a new one.  

Let me know how you make out.

Good Luck,
Michael