So you got it running for nearly 2 minutes...that's an improvement from 20 seconds!
Pull the head off and see if a valve is stuck while you cycle the starter, then you will know for sure.
Take the carb off (or not) and use compressed air to blow out the orifices. Use gumout and blow it through with a rubber tipped blow gun and be sure it is adjusted to start with minimal adjustment to the screws.
I did this with my father in law's generator that hadn't been run for over 10 years and got it to run...without taking the carb off! Sold for good money in my yard sale!
You didn't really try to put fuel to the carb using the pressurized method I described...maybe blowing it out with compressed air will do the trick.
Note: I had a 1450 that had starting issues. I cleaned and remounted the factory (Walbro) carb but it still didn't work. So I bought a "made in chyna" carb and put it on. It started right up!! Go figure...Sold the 1450 in my yard sale as well!!
