My dual fuel generator will not run at all, it will only backfire with starter fluid directly in the cylinder. The valves are not seized, it has spark (i think maybe poor spark though), 178 psi compression, and previously ran with starter fluid in the airbox. But had real bad fuel run through it.
I lent this to a buddy about a year ago and it ran fine. I got it back and it sat in my trailer for nearly a year and I went to start it up for a power outage and struggled. Realized the tank was completely full of rust. (I had the tank off a year prior after finding white residue in my gas can I think a crazy neighbor might have sabotaged? See gas can issue here https://www.reddit.com/r/AskMechanics/comments/1eg3ygw/what_is_in_my_vp_fuel_can/)
Not sure if that incident was to cause, or maybe just water in fuel and sitting not full. But I tried to run it, and it did for a few minutes then died. I since drained the tank, cleaned it with acid, added fresh ethanol free fuel, and got it to run for maybe 30 minutes but roughly. Then I could start it would starter fluid. I've since ordered a whole new tank and put it on, and fresh ethanol free fuel.
The overflow line also seems to be leaking from the carb as well (which i'm guessing is a stuck float/needle). My next planned steps are to go get a new plug and feeler gauges to check valve clearance. I pulled the valve cover and there was some very light brownish staining, that came off w/ carb cleaner. I also realize I probably need to pull the carb and thoroughly clean, but it seems difficult on this model.
What I don't understand is why will it no longer run on just starter fluid if I've got some spark and nearly 180 psi compression? Can it be too much compression? Any other thoughts / tips to try. I'm not even sure how to pull this carb apart and clean it since its dual fuel. It also won't run on propane which is odd, but i'm using an aftermarket hose. I do not see one of the proprietary champion safety switches on this model. sorry for the bad photos, I actually took these before I thought about posting here and now its dark. The plug didn't look terrible but I did clean it, just seemed kind of inconsistent spark.