Regarding your welding of the sprockets. If you take a propane torch (really cheap at a home improvement store) and heat up the piece you want to weld to say 250 - 400 degrees before welding, you can get some good welds with a smaller welder like you're using. This will help get better penetration from the start of the weld. I do this to cheat on really thick pieces for my 110volt Mig and even thick aluminum for my 200 amp tig welder.
You could put the pieces in the oven at 450 too, but don't let the wife catch you.