Petcock in Prime Position Only

[webbmeister25d]

Good morning,

Thank you for permitting me to become a member of your community. I will do my best to contribute at least as much as I receive.

We have just purchased a 2007 GZ250. It has fewer than 1000 miles on it, which indicates to me that it has spent a long time idle. The bike fires right up, and when in the ON or RESERVE position will run for a short while (whilst being ridden) and then stall while underway. It will then refuse to fire up as long as the petcock is on the ON or RESERVE position. Putting the petcock in the PRIME position causes the bike to start almost immediately. Leaving the petcock in the PRIME position whilst riding eliminates the stalling problem altogether. (I do remember to put the petcock in the ON position when parking the bike.)

The bike did receive its 600 mile service. There was very little fuel in the tank when the bike was purchased. I have filled it with fresh fuel and added 4 oz. of B-12. Since the issue is resolved by running the bike with the petcock in the PRIME position, it seems that the issue is related to fuel supply. Then again, I am new at this so ...

Would anyone care to share his or her thoughts on what might be going on here and what I might do to cause the bike to run properly in its appropriate mode?

Many Thanks,

Jim