I bought this bike and it had a blown head gasket. So i removed the head and resurface it and adjusted my valves. installed it back on the bike by the book. The bike started and ran for about 2 seconds then gut off. It did that a couple of times. So i went through the carb and cleaned it up. And it still is doing the same thing. I also checked the vent tubes to check and make sure it wasn't vaperlocking. It's got good spark and plenty of gas. Could it be the throttle position sensor? the book had me check ohms between the green and black wires on the throttle position sensor and it should be between 4 and 6 ohms. it was at 4.36ohms. what about timing? the book had me face the cams opposite of one another with the dots on the cam gears at 9 12 3 with the exhaust cam gear 9 oclock dot in line with the head surface. and the intake cam gear 3 oclock at the head surface. and the crank with the "I" in line. Help please.!!!!!!!!!!!