Yamaha 50ejrs misfire on cylinder 3

[yammerha94]

Hi folks, this is my first post here. I've been browsing the last few weeks and finally decided to make a post hoping for some helpful advice. As stated I have a 94 50ejrs with a cylinder 3 misfire. When running it in the water, it has a very noticeable hesitation starting in the midrange around 3500 rpm, yet. seems to clear up at wot after a few seconds. Running it in the driveway I removed all plug wires 1 by 1 and #3 has no change. Pulling the plug wire from #1 makes a noticeable change, pulling it from #2 makes a more of a difference it seems like. Ive removed the carbs and cleaned them thoroughly, used the oem rebuild kit, set the floats at the correct height, air fuel screws 1+1/2 turns out. Compression is 100 psi across the board. Ive swapped plugs and coils and the misfire stays on cylinder 3. Also put new reeds in, a fuel pump, fuel hose, filter, and made sure the tank is spotless. The spark plug on 3 seems to be wet with fuel while the other 2 look normal as far as I can tell. Any advice would be greatly appreciated!

[TownsendsFJR1300]

Sounds like you covered a bunch..

I would hook up an in-line spark tester(plugs in between the spark plug/plug wire) and check for spark at the time of the issue.
We're trying to rule out if your loosing spark.

Rule this out before proceeding.


A cheaper style spark tester but will work:
Clear part will illuminate with spark (IF sparking) from spark plug cap to plug..

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[99yam40]

did you use a peak reading voltmeter or dva adapter made to take readings on these CDI ignition systems?
Did you get readings on the charge coils and pulser coils?
were they all in spec?

I am not sure if that 50 has 3 pulsar coils (one for each cylinder) to tell it when to fire the plugs , but my 1999 C40 is set up that way

If #3 has good spark when the problem shows up , then it would be a fuel to air ratio problem.
too much fuel or not enough.

a good timing light should tell if the plug is getting spark signal also.

Might try misting a little pre mixed fuel into #3 while the problem is happening to see if that gets it to fire