fastwin 18hp hits the wall at full throttle

[Fastwin]

gday my 66 fastwin dies off when you run it for about 10 minutes at hard throttle. recently i replace the powerhead gasket that goes underneathe the powerhead ( cut my own gasket). the motor runs like a dream for about 10 minutes and then cuts out but runs fine at start then when you give it full throttle it gains speed then cuts back to start. when i ran it in a bucket it was all right so i took the prop off and run it a highest posible throttle without it over revving. ran fine. but when i took the cover off a big plume of white smoke came out. i couldnt see where so i ran it with cover off and couldnt see any smoke. any ideas

 

[OBJ]

Re: fastwin 18hp hits the wall at full throttle

If the smoke smelled like exhaust, the engine is breathing it's own exhaust with the cover on. Was the gasket you made exactly like the old one? A leak in the gasket will allow exhaust fumes up in the hood which will displace the air and eventually stall the engine or cause it to die off as yours does. Take a good look around the base of the power head for any leaks.<br /><br />Other possiblility, is the engine overheating? Pump impeller good, t-stat OK?

 

[Paul Moir]

Re: fastwin 18hp hits the wall at full throttle

Just a quick note - revving the engine in neutral proves nothing, but it can easily damage or even destroy a 2-stroke. Revving causes the engine to run lean and can lead to run-away, where the engine spins up all on it's own to incredible rpms. When this happens there is nothing to be done but to choke the engine, cut the fuel and wait for it to run out. Even disconnecting the spark-plug leads won't help.

 

[Fastwin]

Re: fastwin 18hp hits the wall at full throttle

g'day engine is cooling good and proper and the gasket is identical should i need to use avitation form a gasket on them i only used a little bit on them. so i think its the gasket