1977 Johnson 200 Spark plug carbon buildup

[Lentine95]

Hey all, so got my new to me Johnson running smoothly in a bucket. However, I noticed a few of my sparkplugs aren't looking so good. My top starboard spark plug seems to build up with carbon pretty quickly, while all the others don't seem to have this problem. I don't run it more than 3 min and it becomes pretty discolored. I was running some gumout in my gas, so I switched over to just regular mix gas and it's seemed to have helped a good amount (not as much buildup, but still more than all other plugs). Checked for air leaks in lines and seems all good, also it's getting spark, but when I pull the wire when running it doesn't seem to make any difference (no change in RPM or missing sound). Kind of confused what could be causing this because motor seems to run fine; starts right up, no hesitations when throttling up or down, and maintains idle and higher rpm just fine. Amy suggestions would be great, thanks

 

[Lentine95]

No Title

 

[racerone]

Compression test may give you an answer.-------May not be the answer you want.

 

[Chinewalker]

Those surface gap plugs burn cool as it is. Running in a bucket with no load, you're not likely to build up much heat. A full blast run on the water may give you very different results.

 

[Lentine95]

No Title

Thanks for the info didn't know that. It does stay really cool. And have hose running constantly in bucket too to make sure water does too. But, wondering why if that's the case why that is the only sparkplug to look thay way. All others mainly look like one attached

 

[ondarvr]

As mentioned, check the compression.

 

[Lentine95]

Did a compression check and its at 115psi.Motor was redone by previous owner, all pistons are .20 and all still have honing hatches on walls.

 

[ondarvr]

Normally there's a bit of a variance between cylinders, it would be odd to have all of them read the same.

​Did you check for spark on that cylinder with a spark tester?

 

[Lentine95]

There's a difference between the cylinders but all are within the 115psi - 120psi range. Just the one with problem is at 115psi. Haven't used am actual tester buy have removed the plug wire and can hear spark arcing, also moved spark plug to see if that was problem and same problem happened. Also, gave a shot at moving a different ignition coil and still that had no effect on it. Could it possibly be powerpack just isn't sending enough juice through? Or maybe could just keep it in bucket and run for like 20min to see if just has a real bad carbon build up inside?

 

[Lentine95]

It doesn't sputter, backfire or kick around like it's missing. Honestly wouldn't have even known the plug was dirty if I didn't pull, since doesn't act like any other bad plugs I've had before

 

[Lentine95]

Video of it running

 

[Lentine95]

Video of it running

 

[racerone]

Some will argue.------Remove high speed jet for inspection on that cylinder.------Check the reed valves for that bad cylinder.---Remove bypass cover to look at piston and rings.-Does spark jump a gap of 7/16" , yes or no ?

 

[Lentine95]

No Title

Just realized I had the throttle cable adjusted very poorly making it idle at 2500rpm.. adjusted it better and now the spark plug is looking a lot better. No build up, just fuel and looks to have few little water droplets on it.

However, motor doesn't want to stay idling now and it surges up and down around 1000-1500rpm. Stays running if give little throttle to about 1700rpm. Getting fuel, and primer bulb stays hard so figuring need to pull carbs and give them a cleaning. But now all plugs looking good and not sure if 7/16th gap but can unplug boot while running and can watch and hear spark jumping from boot to plug.

 

[ondarvr]

Primer bulb shouldn't stay hard, it will be soft once the motor starts.

​Clean the carbs, it should idle in gear on the water at 750-800.

​These motors can idle very well when tuned correctly.

 

[Lentine95]

It does get a little soft, like can squeeze a little not rock solid. Also, I "cleaned" carbs once, just let sit with carb cleaner for a little and blew out jets with compressed air, never took out jets.

Figure now would be best I take them out and really inspect and clean. Does anyone know how many turns out they should be once I take them out and put them back in? Think I remember reading once 1 1/2 turns.

Also, think running in a barrel the RPMs should be little higher since its okay under load and circumstances like on water.

 

[racerone]

There are no adjustable carburetor jets on a 77 model 200 hp.-----Not sure where you read about turning them out 1-1/2 turns.

 

[Lentine95]

Sorry, was talking about the orifice for idle. Didn't know if I unscrewed and took out to clean if should be set X amount of turns out or just screw till snug. Or should I just use some thin wire to just clean with them in carburetor and not worry about taking them out