#4 plug black and sooty

[flick250]

I have a 1989 fj 1200 I changed the plugs a couple weeks ago and # 4 plug was black but not wet. I did a compression test and all were 150-160 so I cleaned the carbs put new needle and seats and new pilots and mains synced the carbs. Ran it 150 miles still not perfect so I pulled  the plugs # 4 black I checked the others are fine. I played withe the fuel screws the rest are at 2.5 turns #4 after a half a turn it gets black. Ichecked for spark it looks ok. I cleaned the conections on the coil no help. I pulled the plug wire to each cylinder and 1 2 and 3 the rpm dropped but it didnt change much on number 4. I would appreciate any help I'm running out of  ideas thanks Flick 250

[racerman_27410]

   there could be an issue with the oil control rings on that cylinder.... wouldnt affect compression but could be letting oil get up into the cylinder.

how often do you have to add oil? is the exhaust sooty/wet?



KOokaloo!

[movenon]

First I would put a new spark plug in and make sure the ign. wire and plug cap are in spec. Is the spark produced as good as the in the other cyl ?

Then I would pull the #4 carb off and really clean it, check everything... float height, choke plunger for a good seal, fuel inlet needle valve not binding, float not cracked or leaking, function check diaphragm for correct operation etc.. take your time and check everything.  I think in the "files" section there is a real good write up with photo's on rebuilding the carbs.

As stated it could be a oil control ring. But hopefully its just a carb problem. Think simple... It seems natural to think or gravitate toward the most obscure or difficult/expensive solutions. I think its panic . Black sooty plug = to much fuel, no or min spark, bad plug, oil getting into the combustion area ?

As preventive manit. if I pulled the carbs off I would pull the intakes off and replace the manifold  "O" rings. They are cheap and after 20 plus years I would just do it. It is NOT causing your current problem but might prevent a future problem.

Things to think about

[flick250]

Ive put 600 miles on it since the oil change and it really hasnt changed much in the oil window. I think I'll try a new cap I'm off monday I'll go get one and try it I think they just unscrew and screw in I'll letyou know how it turns out

[flick250]

I checked the secondary checking between 1 and 4 I got 237 kohms I pulled the cap and cut the end and checked it and I got 23k I checked the cap and I got 10k checked the primary it was 1.9 after putting the cap back on the wire it was 33 I also checked 2 and 3 that was 34k I guess I need caps and plug wires should I get them from the dealer or somewhere else. Do the plug wires unscrew from the coil like the caps do. Thanks for all your help flick 250

[racerrad8]

The wires are just 7mm solid core wires, I get mine from my local NAPA store as they have it in bulk. They are glued into the coils and will come out with moderate pulling force. There is a needle down inside the coil that penetrates the wire when you reinstall.

Here are the Spark plug boots

You should switch #1 & #4 wires on the plugs and see if the problem moves to the #1 cylinder. If it does that confirms the secondary ignition system for that coil is having troubles.

If the problem does not move then you are back to carbs.

Randy - RPM

[flick250]

thanks randy I will go to napa monday and get those wires what is the right glue for putting them in thanks flick 250

[movenon]

The wires are just 7mm solid core wires, I get mine from my local NAPA store as they have it in bulk. They are glued into the coils and will come out with moderate pulling force. There is a needle down inside the coil that penetrates the wire when you reinstall.

Here are the Spark plug boots

You should switch #1 & #4 wires on the plugs and see if the problem moves to the #1 cylinder. If it does that confirms the secondary ignition system for that coil is having troubles.

If the problem does not move then you are back to carbs.

Randy - RPM

I agree with Randy. Before you spend the time and money do a quick test to verify. Although on an older, bike new wires and caps wouldn't hurt anything I have given some thought about it myself and I have no current problems. To many years working on airplanes.... Always seemed better to time change out certain items. Its embarrassing when they fail in flight

[wakdady]

Anyone got a pic of these manifold orings?

[racerrad8]

Anyone got a pic of these manifold orings?

Sure, you need not look any further...

Intake Manifold O-Ring

Randy - RPM

[wakdady]

Oh yeah! I got those with my rebuild kit but I have no idea where they go!

[racerrad8]

Oh yeah! I got those with my rebuild kit but I have no idea where they go!

On the back side of the rubber intake manifolds between the head & manifold.

Randy - RPM

[wakdady]

So I gotta remove those black boots to install them?
I gotta come see you in the next couple weeks randy. Watch a doin this weekend?

[racerrad8]

So I gotta remove those black boots to install them?
I gotta come see you in the next couple weeks randy. Watch a doin this weekend?

Yes, pull the heat shield & the allen bolts to remove the intakes.

I should be here, give me a call and let me know.

Randy - RPM

[flick250]

well i put new caps and plug wires I was pretty sure it would fix it but it didnt guess I'm going back in the carbs any suggestions could the float be sinking I put new needle and seats and new pilots and mains I thought they were really clean I took my time I guess I'm pretty bummed I thought for sure the wires and caps would fix it I did switch #4 and #1 the problem didnt switch