I picked up a BF15 a few years ago and have recently gotten around to dusting it off. It started, but ran like crap and died in a few seconds. Out of caution more than anything else I replaced the following;water pump, thermostat, fuel pump, coil and ignition controller. After this it was hard to start but eventually ran okay. The next day I tried to start it again but no joy. I noticed that there was fuel accumulating at the air inlet so I took the carb to a local Honda shop for ultrasonic cleaning and still no luck. Bulb and hose are new. Fuel is ethanol-free. I have a spark on both plugs. Any suggestions?