RE: Who is converting Toro trimmers?
davewallace, your reference to 14mm probably being too much carb is only because you haven't seen my 25cc Weedeater run with a duplicate carb. The weedeater runs as good as you can get one of these things to run, very smooth, good idle, and good throttle response, and it seems to running clean enough that carbon should not be a problem.
I think we are really talking about 14mm being too much carb for the Toro, but the engine ran the same way with the original carb, then I suspected the carb, now I am going to try a different magneto. After the running session was over and I thought it over, it sounded like it could be an electrical problem, and there is only one electrical part. (By the way a good tool for setting magneto gaps is a piece of Aluminum flashing, flashing is usually around 12 to 15 thousands thick.) The Toro has higher compression than the weedeater and I will probably open the ports on the Toro like I did the weedeater. By looking at some of the good references for Walbro and Zama that were posted by other here, you can see that most of these carbs have a pretty wide cc range. I sure am going to try again with this carb. It was not running any worse than the original carb and if carburization was the original problem with this particular engine, I would expect a bigger carb to aggravate the problem further. Did you get the 3 photos I sent you?
One last point, it is hard most of the time to get the intake big enough to fully use the capability of a larger carb as I am doing. This carb has a 9/16" bore but I was only able to open the carb spacer on the Weedeater, for example, to 1/2" diameter. This is one of those things I think we can "get away with".