I’ve owned this quad for twenty years at least. I’ve never seen another one so I’ve not had a chance to talk to someone that has owned one. The black plunger on the right side of the carb is used for? It has always started great on the first kick when cold but it’s always been a bear to start when the engine is hot. I got it out of my barn a couple of days ago and within a few hours I got it to run After cleaning the carb a little. Is the plunger a possible remedy for hot starting?

 

 

Don't know the 250s but many carbs have an excess fuel plunger on the float bowl, works like those red buttons on modern mowers/brushcutters, etc, and squirts fuel into the inlet tract. I see from the parts drawing your plunger is further up, but it is marked "plunger assembly starting"