One plug fouling, wondering why

[Marauder03]

So my new to me 1989 Vmax which I’ve had now about 9 months seem to foul out only one plug. The cylinder on the rear left of the engine as you sit on the bike, I think it’s no.2 I’m probably wrong but anyway that’s the guy that’s fouling the plug. All the others are running normal according to visual inspection of the plugs. So I’ve changed spark plugs since I’ve owned it and put champions in it and I get about 300 miles before I can feel a little miss, then pull that plug and clean it and back to running great. I’ve tried running some sea foam through the carbs to see if that would help. The bike runs really good so I’m hesitant to take the carbs off yet, I’d rather wait until winter for that project if I can. So my questions are should I try an adjustment to the a/f mixture screw first, perform the peashooter or shotgun procedures and maybe set my plug gap at .030 instead of .035 this bike runs really well like I said it is not that big of a deal to pull and clean plugs so that’s why I haven’t touched anything yet, I don’t want to screw this up, other than that one plug this thing idles perfect and will rocket to the high rpms. Any suggestions, advice would be greatly appreciated.

 

[MaxMidnight]

As it is fouling that indicates that something is wrong.

Is the fouling sooty or oily?

Assuming it is sooty then you need to establish why it is running over rich.
If not already done so balance the carbs.
Given that the idle circuit, even if rich, won't be adding a huge amount of fuel at road speeds I doubt if that is you issue but still worth checking unless the tamper proof plugs are still in place.
If they aren't the 2 1/2 turns out is a good starting place.

If none of the above helps then the first thing I would do is to check that the choke plungers are fully seated when off.

 

[Marauder03]

Hi thank you for your reply, I have not balanced the carbs yet and the brass plugs have been taken out already. I probably should have added it has a header which I’m assuming means they had to rejet the carbs. The plungers will be my first visual inspection, I totally did not think of that. I’ll need to get a synchronizer for balancing the carbs correct? Can you recommend one? I’ve been thinking of getting one anyway because I need it for my Madura as well. Thank you.

 

[dannymax]

Carbtune

...Unless you have a stg 7 with the V Boost eliminator

 

[Marauder03]

I do not have the stage 7, I’m not sure what the po did as far as jets or a kit. Would I be wrong to guess a stage 1? It has a header with a holeshot muffler I’m not sure what the set up would be with this type of exhaust. I’ll check into the carbtune thanks for the recommendation.

 

[dannymax]

Couple more ideas, you may have a float level issue or maybe some corrosion on the plug lead ends or in the plug cap.
I doubt a jetting issue as it only seems to be the #1 carb giving you trouble.

 

[Fire-medic]

Try switching the left rear and right rear coils, and see if the 'miss' or fouled plug migrates to the new cylinder.

 

[Marauder03]

Thanks guys some great ideas! I feel kinda dumb now I haven’t done some of these steps already. Maybe I’m overthinking it, I was thinking the float idea the other day only because it be way the bike sits on the kickstand and the carb fouling the plug is the lowest point of fuel to sit but I didn’t think anymore about it. If it is a float problem I assume the carbs have to come off? Is this true? I now have a go take a look at some of these things on my bike, thank you so much!

 

[MaxMidnight]

You can check the float level with the carbs on the bike, the Service Manual shows how.
I ran Holeshot headers and silencers and the bike ran fine without any re-jetting.

 

[Marauder03]

I did just read an article on how to do the float test which I’m going to do as soon as I take this thing for a ride. It is beautiful out today and maybe I can clear it out with some wot pulls. Can’t hurt to try, right. Lol

 

[veebooster]

Long shot here: Open your air box, rev the bike a bit, and make sure your needles are all moving smoothly. Pay special attention to the suspect cylinders needle. I had one hanging up a bit. Caused exhaust popping and carb spitting.