Old cub cadet help

[mogie55]

My neighbor bought his older cub over and said it wont run right.Model #142680399. serial # 2050587 U 73597 With a 12HP Kohler #K301AQ8 engine. When started and Rpms are brought up it stumbles bad and then smooths out then starts to die it will almost die and rebound and keep doing this and then somtimes dies. Working the choke really has no effect . It seems like its starving for fuel. I pulled the carb and checked needle and seat and cleanedthe whole carb. wasnt much sediment in the bowl. Put back together same result. I put a spark plug tester on it and has good spark but when it starts too die the spark appears weak and then gets bright when it rebounds Im now thinking ignition. Maybe a weak coil? Any Thoughts would be greatly appreciated.

 

[bertsmobile1]

The intensity of the spark is proportional to the engine speed
The faster the speed the stronger the spark.
IT will be a fuel problem and being an old mower the place to start is draining & cleaning the fuel tank.
IF you want to confirm it is a clogged fuel tank outlet then get a substitute tank ( off your push mower for instance ) and see if running off that cures the problem .