Having real hard time with Carb.

[05gz250]

Hey guys,I'm new to the group and was wondering if anyone can help me.
I have an 05' GZ250. When ever I try to start the bike I always use full choke, but I always need to keep my hand on the throttle... if I let go the bike falls flat on its face. The air filter looks good, doesn't look like the carb has any "gunk" in it. I have tried adjusting the pilot screw ( on the engine side) turned it out 2.5 turns, seemed to run fine at first, but I don't know if it was because the bike was kind of warm. So I tried it out the next day when the engine was cold, and it failed like usual. So today I brought it to my boss ( a service manager ) and he said it sounds like there could be a leak as when the bike is nice and hot it seems to run fine. I have now currently turned the pilot screw to 1.5 turns. are there any idea out there that could help?

and also, I saw on here that people were getting the bike up to 70 mph but the most I can seem to get it to is about 60 mph... and when ridding at 60 and a strong wind is against me i drop right down to 50 miles even with the throttle wide open. Is this normal for anyone else?
sorry for the long post, just wanted to get everything out there right away.