why does my 1987 johnson 50 run away somtimes

[fpctim]

When i hook up the ear muffs and start the motor and bump the idel lever up to start it,then before i shut it down i will raise the idel up to clear the exshust and it runs very high rpms and i have to dump the carbs to shut it off,why do they run away,this is a new power head as in rebuilt so i cant see it being carb build up

 

[kdrelich]

Re: why does my 1987 johnson 50 run away somtimes

I don't think you have a probelm, with the motor out of the water you don't have any exhaust back pressure and no load on the moter (like in gear).The throttle plates don't open right away,first the timing is advanced which is responsible for about 1000 rpm or so then the carbs start to open when you push the throttle down

 

[JB]

Re: why does my 1987 johnson 50 run away somtimes

Most 2 strokes will go into thermal runaway if revved up enough without a load, Tim. Very dangerous.<br /><br />Never rev beyond about 2000 rpm without a load on the engine. <br /><br />Thermal runaway can be identified when killing the ignition will not kill the engine.<br /><br />Congratulations on your good luck at still having an engine.