I vote for “old gas, and gummed up carb”. I have an old Magnum III 49cc auger.It sat in the garage for 7 years. The colour even went out of the mixed gas, it had sat so long. There was varnish in the fuel line, and the bottom of the tank was covered with a syrup lookin tar. I removed the carb, dismantled it, and cleaned it with Brake Clean. I removed the fuel filter, and fuel line, cleaned the tank of tar, and installed new fuel line and filter. Added some fresh gas, mixed to 25:1, and it started after a few pulls. I set up the carb idle, and it starts great every time. Just thought I’d let you all know…The posts on this site helped me get it working. Thanks!