brendantownsend
Cadet
- Joined
- May 29, 2005
- Messages
- 7
Since known fuel blockages on my Johnson, and following a carb clear-out (though I didn't extract the valves & needles), my engine appeared to run like a top in a water tank.<br /><br />I then took it to the river on the back of my inflatable and it ran like a song for about twenty minutes - both at low speed and near-WOT. However, it was noisy (a sort of clack-clack-clak in time with the ignition over a wide rev-range, including WOT) but was nevertheless running AOK for about 20-25 mins. Then suddenly it went very smooth and considerably quieter, but then a few minutes later conked out and wouldn't re-start for a while. When I did try to pull-start, I did notice blue smoke from the exhaust where previously there was none, and it seemed to be "trying" to fire.<br /><br />Now I'm suspecting intermittent/sticking needle valve for the carb reservoir causing an overflow, flooding the engine and causing a stall - which would explain the blue smoke and difficulty starting. However, I'm bothered by that very rapid clacking-type running noise and why it should then suddenly go quieter and smoother before the engine suddenly stalled a few minutes afterwards and wouldn't restart (though started straight up again after about ten minutes). It certainly doesn't start and idle as though it's running on only one cylinder for example.<br /><br />Is the early running noise possibly related to the imminent cut-out, and what else might I check before we try another river trip to help prevent the engine cutting out again.<br /><br />What about the reeds - could this be a factor? Piston slap?... Would this suddenly cease once warnmed up (sort of like a resonance suddenly being lost).<br /><br />I can say that the spark is very good on both cylinders, and replacing the old plugs with B6HS kept them clean after the trip, with very modest brown deposits on the threaded body and a light-grey ground electrode.<br /><br />Finally, I don't think it's overheating as the pull-start operated exactly as when cold, though the engine casing was too hot to hold your hand on. Is this normal and could fuel be boiling in the carb to cause this problem? I am currently running 50:1 mix (increased from the original 100:1) as originally recommended by Johnson.<br /><br />It's just had a full service and the waterways have just been professionally cleared (so I'm told!!!), plus a new impeller, and it spits water well enough, and a good spark.<br /><br />Any ideas?<br /><br />With thanks,