I have a Shindy T270 that has run poorly from the start. My dealer couldn't fix because he was uneducated on the new carbs. The newer T270 has plug (Welch plug) over the high speed jet sothe consumer does not adjust the jet settings. After the plug was removed and the carburetor mixture adjusted, it ran like a scalded dog. Not all carburetors have adjustable jets, but I bet there are others with the same problem I had that are suffering through it. For my model you just drill a 1/8" hole into the brass plug. Just drill deeply enough to stick a small screw driver into it to twist it out. Voila three the adjustment screw is. I am told that many lawnmower also have Welch plugs which can be removed to adjust the fuel mixture.