The bike had been sitting for about 18 months. We did put in new fuel. We had it out last weekend and at first it was running fine. After about 25 minutes, it would shut down for no reason. The only way to get it to restart was to use the choke. The ambient temp was about 87, and the bike was completely warm, so the choke shouldn't have been needed. Even with the choke, it was very hard to start. Once started, it would run fine for a short time, then just shut down again. Then it was choke, kick many times, ride for a few minutes and the cycle would go again. Today is the first day I'll have to look at it. The air filter looks good, I'm going to pull the spark plug to see if it is fouled. Anyone have any suggestions on what to check first? Thanks in advance.