Stick and TIG require constant-current (CC) type machines. MIG on the other hand requires constant voltage (CV), Some engine-driven welders come with a "constant voltage adapter" that will allow you to MIG weld as well, but some do not. This is something you should ask about when you buy a machine, does it have a CV output as well.. I believe a CV adapter comes as an optional extra on the SA200 but not all of them have one. I think a CV output is standard equipment on the Bobcat 250. Note that engine driven power supplies are rather expensive in terms of initial price, fuel costs, and maintenance such as oil and filters and such. Unless you're planning on welding on-site most of the time, It would cost less to buy a power supply that plugs into 220v wall current for your own personal use. If you don't have a 220V outlet in your garage, you can buy a 220V extension cord and run it from your dryer outlet. Most dryers run off 220V. Or hire an electrician to run a 220V line from your breaker into the garage. To a certain extent you can TIG weld with any stick welding CC power supply. However to weld aluminum it's generally preferable to have an inverter type power supply that is designed for TIG. Welding aluminum requires AC + high frequency. You can actually use those old AC "buzz boxes" to TIG weld aluminum, but you need to also have a high-frequency adapter. Without the high frequency, TIG starting is almost impossible with AC. Frankly, a lot of welders use 6010 for the root pass....because they're ignorant. Or because the companies they work for don't have a weld QC process that they know of. This is an antiquated practice which hasn't been updated in nearly 70 years. Welding technology has changed a bit since the 1940's though it seems some welding companies haven't. The most up-to-date pipe welders use MIG for open root passes, and all-position dual-shield FCAW for the fill passes. This is typically 2-3 times faster than stick welding, and you don't need to worry about start/stop locations. You use short-circuit MIG, w/ 100% CO2 for vertical-down root passes. You MUST ensure a consistent 3/32" root gap all the way around (a good practice no matter what process you use.) Also when you make your tack welds make sure they're nice and beefy, at least 1' long. Little tiny tack welds won't do, you need good solid tack welds to prevent the gap from closing up as you fill the root. The first place a weld inspector is going to look for defects is in the tack areas, That's where defects like root cracks and lack-of-fusion are most commonly found. Also be careful not to get bits MIG wire stuck on the inside of the pipe, those show up like a sore thumb on x-rays. The way you avoid this is by using a consistent "drag" angle for the MIG root pass, and by being careful never to get ahead of your puddle. Use E71T-1 dual-shield wires for the vertical-up fill passes.