You could try getting them off with a 6 inch gear puller. It might break the tines loose, but if they're really stuck, the puller might just bend the metal on the tines. The puller in the picture cost me about $15.00 a few years back. Otherwise, I'd suggest taking the tiller to a well equipped small engine repair place or machine shop.

Thanks for the tip. I have a six inch gear puller on the tine (as in the picture) but it still doesn't want to move. I was thinking about heating the tine with a torch - maybe that would loosen it. Is there any down side to doing that (am I going to damage anything)??

There's an oil seal on each side of the transmission where the tine shaft comes out. I'm guessing they are neoprene/metal seals (like a wheel bearing seal) and probably wouldn't stand the heat very well. Here's a link to an online parts catalog for the transmission for the FG110A tiller: http://www.jackssmallengines.com/Jacks-Parts-Lookup/Model-Diagram/HONDA/29334/5900. The oil seal is item 14.

If you want to try the heat, you may want to separate the transmission from the engine. There are four bolts at the top of the transmission (on the under-side of the tine shroud) that screw into the engine block. Take those out and the engine and transmission will separate. The coupling between the engine and transmission is a simple centrifugal clutch and comes right apart.