I have had my Terrapro for a little over a year now. I used it all last summer to mow around 4 acres without issue, besides replacing belts. I have used it since as just a 4 wheeler this winter and spring and it has ran fine using the thumb throttle. This last weekend I attempted to mow with the Terrapro, and as soon as I engage the lever throttle, the engine constantly surges and runs horribly. I removed the carburetor and soaked it in pinesol for a day. It still starts and runs great on the thumb throttle, but horribly on the lever. I removed the lever throttle linkage to the thumb throttle, and it still runs horribly as soon as the lever throttle engages the transmission.

I noticed there is another "throttle plate" after the carburetor in the intake. It appears that the only input to this "throttle plate" control module is transmission speed signal from a cable. It my issue likely due to a fault with this "module" between the intake and carb? Any tips before tearing into it?