I don't know if your HM100 uses the same carburetor as the HH100 models but on the cast iron HM100, HH100 and several other models, if you removed the center nozzle from the carburetor when you cleaned it, you were screwed. Some of the fuel passages were drilled with the factory nozzle in place so if you removed it, there is virtually no chance of ever installing it back into that exact same position. This was a common headache with most Tecumseh carburetors. Any time you rebuilt the carburetor you had to install a replacement "Service nozzle" which you probably couldn't find because they haven't made those for quite some time now. Perhaps yours is different, I hope so because it sounds a lot like you're having those same kind of issues. Stens may possibly have a service nozzle? I don't know, they used to have a lot of stuff for the older engines. Either way, I'd install a K series Kohler carb in place of the Tecumseh carb. It's an easy swap, I have the Chinese made Kohler K series carbs installed on a HH100, HH120, and a HM100. I plan to install one on an OHV160 when I get around to working on that one.