My grandson has the above four wheeler, when cold won't idle. If you idle up when cold, the idle is too high when it warms up. Any ideas?

 

I have the same machine and this is what works for me.
First,make sure the air filter is clean,then start the quad with the choke fully out,push in about 1/4 of the way to see if it will stay idleing.
If not, start and give a constant rev to keep running and adjust the idle adjustment screw on the carb ( toward the top of carb) and adjust enough to allow the quad to stay running on it's own
You probably will have to make another adjustment after it warms up but it should be fine after that, mine always seems to be.
Hope this helps