Tucumseh Enduro 17.5hp, started missing yesterday and today began uncontrolled full throttle. Didn't know the engine could run that fast. Only thing affects it is moving choke lever on carb. Throttle cable has complete free run. Starts on choked start position and then revs uncontrollably. Moving spring on govenor has no effect. Any ideas?

SOURCE: starts on choke but dies when moved off choke

If it will start on choke and die when choke is taken off...the carb needs to be taken off and cleaned. The main jet in the carb is probably clogged.

SOURCE: Stops when given full throttle

Most likely carburetor needs adjustment.

SOURCE: 31cc Ryobi weed eater engine will start, then stall shortly after

you need to adjust the carb ,look for small screws around carb turn out 1/4 to 1/2 turn good luck

SOURCE: Craftsman mower with 20hp B&S Intek won't start/run

That throttle cable issue sounds like it may be the culprit. the cable housing (the outer casing for the wire throttle cable) may not be anchored correctly. Which may be allowing you to move the throttle without any change at the butterfly control on the carb. make sure the cable housing is anchored at both ends.. by the throttle control and at the carb area.. That may be your problem... hope it is that simple...
K

SOURCE: I have a DYT400 with a Briggs and Straton Intek plus 19.5 ovh. When I move the speed lever to full speed, the mower wants to choke out. Also, when I put the lever on stop, it just keeps running. the

You have governor with a missing spring or it could be in the wrong place. If the springs are all OK then you may have a bad governor gear in the crankcase. This engine is bad about the governor gears bending the governor gear shaft.