Engine RPM seems to be pulsing

[Navigator]

Hi all,<br />Got a strange one thats been happening for the last month or so. It a Honda 40, Tiller. Between 1000 and 3000rpm, doesn't matter where, If I hold the throttle at any given position, I'm getting a slight pulse in the RPM, Kind of at the rate of "one-and-and-two-and-three-and...". RPM's according to the tach seem to be holding steady, but theres a definite fluctuation going on. Hit the throttle and the acceleration is instantaneous so it must be something minor. Usually it doesn't happen at idle, only when I'm at no-wake speeds.<br /><br />Could I be getting a carb out of synch? I've ruled out the obvious. I've put on a brand new prop, the prop shaft is not bent. Primer buld is hard, not a fuel delivery problem. Gas tank is vented. Other that this, the engine runs smooth as ever.<br /><br />Anyone ever had this type of experience?<br /><br />Nav

 

[jim dozier]

Re: Engine RPM seems to be pulsing

Have you tried adjusting the idle mixture? It sounds like the mixture may be a little off. Can't tell from your description whether its too lean or too rich. Run the engine at the rpm that causes the problem and then kill the engine and pull the plugs. The plugs may give you some insight as to which way to go with the mixture. My first guess would be that they are lean.