Need help with atv please!!!?

I have a Honda fourtrax90. I haven't started it in about 3 years. I am selling it now but there is one small problem. It usually fires up fine but i have to keep pumping the throttle to keep it running. If I let it idol all the way down then push the throttle it, it stalls. I have to keep doin this for a good minute or two before I can shift ino first. I have the same problem in first. If I let it idol all the way down sometimes if I pump it really hard and fast it won't stall but if i just push the throttle in it will. It goes away a little bit after riding for awhile. Any help is greatly appreciated. Thanks.