Christmas Grizzly

Hey everyone, hoping to get some help here... my kids 03 KTF 50 Quad has always ran great... they were riding it a couple of hours a few days ago and it died a couple of times (not normal) but started right back up. A few days later my 5 year old wanted to take it for a spin so I started it (2 pulls) and he took off.. he made it a couple hundred yards and it died and we havnt been able to start it since. I have new gas, good spark and 120 psi compression.. it will not start with starter fluid in the intake or even in the cylinder.. the fuel bowl has fuel at the carb... what am I missing? It’s driving me crazy!!

Went shopping on Saturday, picked up another Kawasaki Bayou 220 and a Yamaha Timber Wolf 250
I really should sell some of these but they are a lot of fun to find, fix and ride
Of course neither of them run but that's part of the fun!  Az

The small waterline insert for the hose that goes from the water pump cover to the thermostat housing has corroded off. I only need the insert on top and behind the thermostat housing that the hose goes over and can't find just the insert. It looks like it may be pressed in. I've have been told the entire motor housing needs to be replaced. The pic with the red line indicates where the hose and insert would be and the insert looks like the pic of the water pump  Any ideas would be really appreciated.