I have a 2006 Grizzly 660 with 220 miles. When I start it the first time of the day it is difficult to keep running.

This last weekend was typical. 65 degrees, put 1/4 - 1/2 choke and start the bike. if i don't touch anything it will die, if i try to feather the throttle it will die. I usually have to restart it 4-5 times while trying to feather the gas before it will finally run.

Once it is warmed up it will run fine for the rest of the day. The only thing that has been done to the bike was an oil change and I used 40 weight yamaha oil per the dealers recommendation.

 

Do you store your quad with a half empty tank? In this weather condensation is a big factor. My guess is you"ve got a little water in the bottom of the carb bowl. I'd drain the bowl using the screw on the bottom and drain the gas tank and fill her up with new gas and try that.

 

Friday evening I put on 35 miles on the bike, then it was hard to start saturday. saturday afternoon put on an additional 35 miles and hard to start on sunday. water shouldn't get in that quick should it?

 

Unless it's had water in the hole time. I'd still drain the bowl and start from there. Then I'd change out the spark plug. I've had several quads foul the plug on a new bike before there broken in.
Is your bike still under warrenty? If so, let them figure it out. I'm sure it's something simple. Might check to make sure there is no air leak on the boots to the carb. Tighten down all the screws leading to and from the carb and the air box.

 

Is the bike always fine after it warms up?? If so, it could be that your valves need adjusted... I've had that issue before w/ my 02 660... and the valves were a lil tight...