Whats a good fuel additive to mix in with the gas every so often to clean out the carb/lines/engine and such?

I see some posts regarding seafoam but it seems like a mixed crowd, the same amout that like it seem to dislike it, anything else that will work well?

 

Seafoam is good stuff as is Yamaha Ringfree. Don't try to drown your engine in the stuff and you'll be fine, just a little in every gas tank will clean out the gunk over time.

 

Fuel lines and the engine should never need to be cleaned ( inside anyway). If the carb needs cleaning, take it off and clean it. If you engine needs cleaned inside you need to tune it better or rebuild it.