Engine Gx270 won't start

I have a Karcher power washer with a Honda gx270 engine. It won't start and I'm stumped. I've replaced the carburetor, spark plug, coil, on/off switch, oil sensor, oil change and a few curse words. What could be the problem?! I used it last fall with no issue and now nothing. The pump isn't seized, I got compression and spark. Please help me figure it out I'm going crazy!!

Some basic troubleshooting is easier and cheaper than throwing expensive parts at it. You need compression, spark, fuel and air in the proper amounts and the proper time. What is the compression? If you don't have a gauge remove the rewind and spin the motor backwards, it should hit compression and bounce back. Squirt some gas or carb cleaner NOT ETHER down the carb throat. Does it fire? Remove the valve cover and check the clearances, maybe a push rod has popped out of place.

Hello all. I'm new to your forum and having a look through the posts and hoping to learn a lot.
My son repairs quad bikes and the odd mower. A lot of the problems he solves (especially in the spring) by draining the stale petrol and replacing with fresh. I don't know about the US but here in the UK petrol doesn't stay good for many months any more and diesel contains a percentage of biodiesel which grows an algae if left over winter when there may be some moisture in the tank. It's a damn nuisance.

Gas/Petrol is the same way here in the USA. It used to that you could store gas for several months, and then it became don't buy more than you can use is 30 days, then it became 14 days, now in some cases it is 7 days. Diesel has the same issue with biofuels and algae growth. I think the rule is don't store more than 90 days unless treated, and that would be questionable sometimes.