An update: Machine still very solid. On my 2nd 150 cf bottle of gas. WARNING: TIG welding is addictive! Kenny told me that once I got familiar with TIG that I wouldn't use my arc welder anymore and I think he was right. Today I TIG welded steel to repair a foot peg for a Suzuki S40. 3/8" plate cut to about 3/4" wide. Set the machine on DC and 135 amps. Wow, I used filler on the first weld, but on the other side I just melted the two pieces together. Cannot even tell it was welded.
Found out one of the aluminum plates I have been trying to practice on was laying in a puddle of mud mixed with diesel for about 6 weeks. What a waste of time and argon. No amount of cleaning and brushing would stop dirty, porous welds. Now if there is some trick to cleaning a piece of aluminum like that I'd love to hear about it since I'll probably be asked to repair an oily chain guard or clutch cover at some point.