danielplace

I hope you have flooded the engine with a awful lot of water dispersant(rustoff, wd40, CRC, corrosion X) and oil before the 3 days passed. The raw steel bearings with water can be ruined in that time. Rust is a high rpm ball bearings worst killer. Was the engine completely shut downwhen it ingested water. Hydralicing these engines can destroy a engine and it might still run fine but blow later from the bearings indenting the rod or races. We hope that is not your case.
Lets see what is going on that it won't pop. You need good compression of clean fuel and spark(check that you have good spark still) for this to happen. I would start by being sure the bottom end is flushed and dry other than some fumes we hope to get to fire. Take out the plug and bring the piston to the top and turn the engine carb up and about a couple ounces of gas/oil premix, now upright the engine and very slowly pul it through for a minute. Now hold the engine upside down with no plug and pull the rope rapidly for 15 seconds or until there is only mist and no liquid coming out. Reinstall a dry plug make sure you have good clean gas at the carb. If the engine still won't fire after half a dozen pulls with no choke then pull the plug and see if it is wet or dry and either dry it off and retry or if dry reinstall and choke engine and try again. Have you checked tat flywheel key is not sheared as it will have fuel and spark but still not run because the spark is out of time. Some times you can have carb issues that will not allow a engine to run that is why many times it is best to just get it to fire with small shots of fuel first and when it will run like that connect the fuel line to the carb and see if it still will run and idle.