Only 1 Sparkplug Burned Up?

[Jetjon24]

I have a 1998 GTX LTD installed in a 14ft jon boat. I bought it 9 months ago with the engine and pump (lower half of the ski) installed, but the engine had sat for 2 years at least. So far I bought a key, rebuilt the jet pump (twice), cleaned the carb. I finally got it pulling fuel and running on that a few weeks ago. The engine ran away on me (didn't shut off when i pulled the key, revved up really high, and scared the crap out of me) but i shut it off after frantically jumping in my boat ripping out fuel lines. I took it out on the water and after running out of both gas and battery while trying to start it, i gave up and tried again the other day. I got a new battery and ran it today. The boat has some trouble starting, it bogs down at low throttle, and when racing a skiff with a 20hp motor, it lost. It gets on plane but it is ridiculously slow for a 130hp motor. When trying to figure out the issue the first thing i did was remove the spark plugs. One plug looked in pristine condition with a nice glimmer of oil on it, and the other was black. This seems like a really serious problem. Am I only running on 1 cylinder? What would cause this to happen, and what should I do to fix it?

 

[Ankeneyou]

Do a compression test first. I'm betting at least one cylinder is toast. you should have 130 to 135 psi on a fresh 951. Anything below 105/110 or so you'll have a tough time starting in water and low power.

 

[Chester]

Next time it runs away, pull the choke to kill the engine.

Chester

 

[Jetjon24]

I called my boat mechanic and he said that on these 2 strokes, the spark plugs are supposed to turn black. I ran the engine and then pulled the cap on the spark plug that was clean, and the engine kept running the same. The engine stopped when I pulled the cap on the black plug. The plug that was black was working just fine, so i guess the clean plug is clean because it isn't sparking. I noticed that I had two places to ground on my ignition coils, but three wires were grounded to one side of the coil and there were no wires grounded to the other. Is this my issue? I looked through the manual, but couldn't figure it out. And thanks for the advice on it running away. It only runs away on the trailer, it is fine in the water.

 

[mikidymac]

So these ignitions fire both plugs for every compression cycle. The spark isn’t your issue. Typically one plug is white because it’s running lean and that cylinder isn’t getting enough oil/fuel mixture. It will eventually seize that piston.
99.9% of the time it’s from a dirty carb and/or fuel system.

 

[Chester]

Try new spark plugs. Sometimes even a new one fails. Also, test the resistance of the plug caps and the ignition coil. Have you tried cutting back the plug wires a little?

Chester

 

[Jetjon24]

Yesterday i did a compression test, I got about 135 on each cylinder. I took the sparkplugs out and held them against metal and they both sparked. I sanded down the grounds on the ignition coil. Also, I unplugged the cylinder with the "working plug" (the black one) and sprayed starter fluid in the other, and it started and died off. I just recently had my carbs rebuilt and I replaced the fuel lines. The only thing I haven't touched is the oil system. Long story short, I have good compression, I'm getting at least some spark, and my fuel lines and carbs shouldn't be the problem. One of my friends who's a good mechanic is kinda baffled and he said maybe It's just the fact that you are running a twenty year old motor that has sat for over two years and it will just take time and seafoam to clean it out. There aren't any issues from the oil system that would cause one cylinder to run fine and the other to run lean are there?

 

[Jetjon24]

Also, Happy Easter. I am going to replace the plugs again, I have not cut back the wires, and I am going to have a friend come over who has the stuff to test resistance.

 

[mikidymac]

Do not run seafoam it will remove the 2 stroke lubrication oil. There is nothing that a fix in a bottle will cure in these skis.
I still suspect carbs.
Did you rebuild with genuine Mikuni kits?
Did you install genuine Mikuni needle and seats?
Did you replace the springs?
Did you check popoff and leak down?

 

[wrench2ride]

check your reed valves, if you reeds look good then I would bet your problem is in the carbs.

 

[Jetjon24]

Update... I Removed the carb and found some interesting things. 1st, the reeds were good. 2nd, the plate that opens and closes in the back of the carb (the throttle plate thing...) that goes to the LEFT cylinder was tarnished and faded, and the one on the RIGHT was shiny (I'm attatching pictures). Also. The little metal piece that sticks up in the engine between the carb and the reeds (I have pictures of this too because I'm probably not making any sense) in the LEFT cylinder it is 100% dry and in the Right cylinder it is all shiny and oily. So a recap of everything
left cylinder: black spark plug, runs by itself, everything is tarnished, and the small metal piece that sits between the back of the carbs and the reeds is completely dry.
right cylinder: Clean, shiny, oil covered plugs, everything is shiny in the carb, it starts but doesn't run when the other cylinder is unplugged, and the little metal peice between the carb and reeds is oily and shiny.
I am very confused on what the issue is here. Why is the cylinder that's not getting oil the one that is black and also the one thats running better? Why would a cylinder with a lot of oil that fires up not continue running? I'm pretty sure my carbs are set to what the manual says. Any Ideas on whats going on?
This is the metal peice in the LEFT cylinder

This is the metal peice in the RIGHT cylinder

 

[mikidymac]

First I can see you still have tempo lines which is bad and you haven’t changed the old oil injection lines either, also bad.
The nipple in the last pictures is the oil injection. If it’s dry you are not getting any oil. Also if your butterfly on the carb is dry then you aren’t getting any fuel. I don’t think your carbs are clean and/or working correctly.

 

[Jetjon24]

Ok. Thanks. I'll look into the carbs. If the oil injection is dry, do you think that might just be that one of my oil injection lines is clogged or do you think that is something wrong with the pump itself? Also, my boat mechanic said he thinks that he could remove the oil pump and i can run premixed fuel. Is that something you can do with skis? Would you recommend this? Also, thanks for putting up with my excessive random questions, I don't know much but I am here to learn.

 

[mikidymac]

No, don’t remove the oil injection. I have never seen one side go bad on the pump but you can put the pump on a drill to verify flow. Also spray the brass check valve in your picture from the clear line with brake cleaner to make sure it isn’t plugged.

 

[wrench2ride]

I agree with mikidymac, don't delete your oil injection system, it is a pain to be mixing fuel and you will end up having it run too rich at low speeds and too lean at w.o.t. your running issue isn't the oil injection system but that is something we need to verify since you say it looks so dry, it will cause an issue if you continue to run it without lubrication.
Go through your carbs and and replace the fuel lines, that would be a good time to verify your fuel shut off valve also.

 

[Jetjon24]

The oil pump is all good. When I removed the oil lines, they were both full of oil (which made a mess). I was adjusting the carb and the low speed screw on the left carb was squeaking and creaking when I turned it. I removed the needle and cleaned up that spring. Then I reinstalled it and it was sitting in a different place. Maybe the dirty spring made the person who set it last feel resistance before it was all the way in so he adjusted it from that point and left the low speed set to enrich the mixture way more (he didn't tighten it enough), therefore making that cylinder and carb be the one that is turning black. Does that make any sense? Does that sound like my problem? I can't test it until I can get new fuel lines in the carbs (the grey ones were in descent shape but had a little of that blue gunk)

 

[mikidymac]

Absolutely not! Don’t run it again without correctly rebuild the carbs and fuel system. You have been warned.

 

[Jetjon24]

Ok. Maybe if I just rebuild everything in my boat two times over it will work. I've alredy rebuilt my jet pump twice! So from what I've read, I need to use Mikuni kits right? Anything else I need to know? Last time I just paid someone to do it, but apparently that didn't work...

 

[mikidymac]

Take a look at my carb thread below "Carb Rebuild How-To"

 

[Jetjon24]

Thanks for all the help. I checked it out and it will be really helpful for rebuilding in the near future. I just noticed one REALLY big thing though... I had a small nipple on my carb that didn't have a fuel hose on it. I went back to the forum I used when I redid my fuel lines and I noticed that the 1997 GSX duel carbs were slightly different than my 1998 GTX carbs. I am posting the picture of the nipple that had no hose. Could you please tell me where this line plugs into? I have looked all over the carbs, engine body, internet, and manuals, and i can't figure out where this dang line is supposed to go. Thanks.

 

[mikidymac]

That is for the accelerator pump. It connects to the 90 degree fitting on the carb body in the same picture. You have to use the restrictor jet that is in the hose you are missing to connect them.
If you don’t run it you have to cap it off and rejet the carbs.

 

[Jetjon24]

Wow... I didn't see the 90 degree fitting till you pointed it out. That is definitely a problem. Do you think that accounts for all of my problems or do you think there is another deeper issue behind it?

 

[mikidymac]

For sure. Air and fuel leak on that carb is a huge problem.

 

[Jetjon24]

Awesome! I'm looking for the restrictor jet that I need to buy. Is this what I'm looking for? (#72 "Recharge Jet") If not, what is the part that i need? I couldn't find anything called a restrictor jet. BTW, Thanks so much for the help.

 

[mikidymac]

Yes, that is the part.