i just bought a used red cat 150 for $200 for my sons and it is not running. the lady i got it from said it was running when they parked it. i know the battery is dead and the gas is old so i was going to start by changing the gas and spark plug cleaning the carb and charging the battery, what else should i check out first? does any one have any experience with these quads?

The oil level.

oil is good, clean, and full

yea i delt with the same thing with a 200x back in march, bought it cheap off someone who jus put it in their shop.
first id say pull the tank drain it and clean the inside with somting. then pull the carb off and break it down and clean it really good, making sure no jets are clogged, a carb rebuild kit will help alot too, soak it in some carb/parts cleaner for a while if you have any if not get some, it helps alot. after that if you have a good charged batt and good spark, good fuel and clean carb no reason it wont crank.

and the oil, but i personally would run it for a min or two to break it up a little so it will drain better. JMO

-Nicholas

Assuming its been covered and not out in the weather else you might want to make sure there is no water in the oil.

Otherwise check the air cleaner too. And coolant if there happens to be any.

Otherwise you should be good to let her rip.

On something that has been sitting awhile, I usually pull the plug and shoot a little oil into the cylinder before I turn it over.