I say "welder" issues because I am certain the problem is going to end up being operator ignorance. I'm running a Clarkeweld 130EN, .030" ER70S-6 wire with 25% CO2.
When I ran into the problems about to be listed, I was constructing a roll cage inside the car with DOM .095.
First problem I was running into was when I was under the dash bar trying to get it welded, the arc would cut out and the wire feed was making a ka-thunk ka-thunk ka-thunk in time with the arc starting again. My first thought was that I had a bad ground, but I'm using the bare braided wire method Jody talked about it in one of the videos, and it had been working just fine when welding the front side of the bar. Frustration got the better of me and I shut off the machine for awhile and went back inside. Came back out maybe 20 minutes later, re-positioned and got the section finished.
As far as I know, the Clarkeweld machines do not have a thermal cut off. There is no warning light and no breaker.
I am running a dedicated 20 AMP circuit breaker (solution to another irritating problem i had been having) and was plugged into the receptacle less than 15 feet from the breaker with a 10 ft. extension cord rated for 16 amps. I've welded a decent amount with this set-up to know it is not the problem. I also tried playing with the stick-out and gun angle, but no avail.
Later, I was welding another section of the cage which required an overhead position and started getting the same problem. I looked at how the lead to the gun was routing and there were no real tight bends that should have been interfering with the wire travel, but the lead was a little stretched. Moving the welder to the other side of the car seemed to help. The key seemed to be, once the arc got consistent, to just run it.
The second issue I had, was a sudden onset of spatter. Like, remove anything remotely flammable from inside a 100ft radius, spatter. Even the anti-spatter spray wasn't helping. Even after turning down the wire speed a bit, the spatter (more like shower of sparks) seemed to be worse than normal. I was running 3/650 (Voltage setting is a 1-4 notched dial with no indication of what each number is, wire setting is infinitely variable from 1-10 so assuming 1=10IPM, I was sitting about 6.5 on the dial).
I have 2 more bars to install before i can weld the cage to the foot boxes I made, after which there are 4 more bars to install. Given past experience, I anticipate issues with these first 2 bars, and welding the cage to the front boxes due to the cramped nature of the install.
If anyone is left reading this, do you have any tips, experience to share?
tl;dr: Inexperienced, self taught welder running into what could be wire feed binding issues, but can't be sure.
There are one or two more random instances that I run into, but I'll save those for another post
I did end up re-finding out that this thing has a 40% duty cycle at 60amps. Which clears things up to about the consistency of mud. For every 4 minutes of welding, it needs 6 minutes of rest in a 10 minute period. Why is this as clear as mud? Because I have absolutely NO clue as to which setting runs 60 amps. :bash head against brick wall: It does have something printed under where the torch lead exits the unit as "Thermostatic Protection" but that means absolutely nothing to me as there is no warning light, or circuit breaker (as previously mentioned). So part of what I think was happening was that it was overheating. 
