Need Help! I have a 2003 T60 Yamaha. When first cranked, it runs for about 15 minutes at 1500 rpms and runs good with no alarms concerning oil or temperature. A good stream of water flows from the pilot hole consistently. Engine then, just cuts off. After 3 minutes, engine will crank and runs smoothly at any rpm for about 3 minutes. Engine then, turns off.
Already checked temperature at motor with heat gun and temperature is not excessive. Fuel flows good and is clean. Can anyone help?
Certainly sounds 'electronic' in nature...maybe a faulty temperature sensor is turning the motor off after that set time. Other items to check would be ignition wires, coil(s) - if you have multiple coils I would rule that out - and perhaps a faulty engine kill switch circuit.
From your symptoms I would say it sounds like some kind of thermal problem in the electrics (overheating coil?). I am not familiar with the Yammys but you may want to go to an electronics store and pick up a can of that freeze spray that is used to troubleshoot overheating electronic chips. When the engine quits, try spraying various electrical components and see if you find something. You would NOT want to spray the engine block or head... you may crack something. If you are not getting alarms and it is a thermal problem, the cause is probably not mechanical anyway.
Had what you discribed just today on my honda 50. After alot of looking and poking at wires and switches I realized that I forgot to open the air vent on the fuel tank.
You might also want to check that the breather valve is open on your fuel tank. If not a vacume will build up and cut off fuel to the engin. After a few minutes enough air will bleed into the tank to allow you to start it again and run till the vacume gets strong enough to shut it back down. I did that my first season and it had me a little worried till I figured it out. I was out a long way when I changed tanks and ran into the problem. Not where you want to be when you have an engin problem.
Need Help! I have a 2003 T60 Yamaha. When first cranked, it runs for about 15 minutes at 1500 rpms and runs good with no alarms concerning oil or temperature. A good stream of water flows from the pilot hole consistently. Engine then, just cuts off. After 3 minutes, engine will crank and runs smoothly at any rpm for about 3 minutes. Engine then, turns off. 
