If it was my shop I'd happily fire up the mig without checking the wire diameter, feed rate, or voltage. The moment I pulled the trigger I'd notice the gas tank is still on the bike, drop the gun in a panic and leap back a few feet expecting ignition. After a few minutes I'd convince myself an explosion wasn't imminent and I'd remove the gas tank. I'd pick the gun back up, line the wire up with the crack, then flip the visor up and down about 15 times to see if it's still lined up before pulling the trigger (really need to get one of those fancy auto-darkening helmets). I'd finally say "screw it" and pull the trigger, at which point I'd see I'd moved the wire about 1/2" from the crack. Keeping the trigger pulled, I'd leave a trail of molten metal along the frame up to the crack. I'd now be in full Rice Krispies Mode with a sounds of snap, crackle, and pop filling my shop. I'd stop after I'd traversed about half the crack length, flip up the visor, and admire the pile of BB's I'd managed to attach to the frame. Satisfied I was doing my best, I'd drop the visor and continue on with the rest of the crack. Next, I'd pull out the body grinder and flatten the pile of BB's leaving a flat area with the space between the BB's forming a meandering criss-cross reminiscent of a dry lake bed. At that point I'd try to bolt all the sundry items back up to the frame and find that none of the holes lined up. Out comes the abrasive wheel to cut the frame back off and the whole process would be repeated. After 3 or 4 iterations I'd reassemble the bike and shove the welder back into the corner where it could hibernate a year or so until my next welding job. I'll have forgotten to pick up some paint so I'd promise myself to get some next time I'm at the store so I could properly finish the job. I'd use the phone in the garage to thank dad again for giving me his 20 year old Harbor Freight welder. A couple months and several wet rides later I'd notice the rusty weld while servicing the linkage bearings and promise myself I'd pick up some paint next time I'm at the store.
So if anyone needs some welding done in the midwestern US, just give me a shout.