Fouled plug, where to start?

[VentureBob]

Went on fairly long trip last weekend and notice the bike was sputtering a little and had a little backfire once in a while. Anyway, I pulled the plugs and found that the front left was much darker then the rest as you can see in the photo below.

 

Some history, I replaced the TCI with the new electronic one from the group buy, I run a shot of seafoam with every gallon of gas, I only use Premium fuel. After replacing these plugs today, I installed Skydocs Shim Mod on the sliders and since the Torx screw was not present I have to assume the previous owner was already into these carbs. Diaphragms looked new with no holes at all.

 

I do have a set of new NGK spark plug wires I bought from ebay but i have yet to install them. I know I will need to have the carbs synced soon, but I am having trouble finding a dealer that will work on this vintage in my area.

 

http://i906.photobucket.com/albums/ac264/bobandlou3/IMG_0368.jpg

[timgray]

Premium fuel is not helping. Premium burns slower than regular gas and can cause issues.

 

If your carb sync is way out of whack, that can easily cause plug fouling as it's dumping more gas into that cyl compared to the rest.

 

Syncing the bike is not hard at all if you get the right tool. http://www.carbtune.com/

 

In fact a carbtune is cheaper than any dealer will charge you to do the job, and honestly you will tune it better than the dealer will. Most dealer mechanics are not perfectionists.

 

Also, when was the last time you had the Carb diaphragms replaced? Mine looked good, but the bike would not keep sync. I replaced them this weekend and the sync was easy as pie, plus the bike has never ran so good.

 

Seeing you ride an 85, they may have holes or leaks in them causing problems.

Edited May 29, 2012 by timgray

[tz89]

Have the protective caps over the mix screws been removed? That would suggest that the PO was in there adjusting. If so, you might count the turns in and report back. Maybe #2 is set too rich.

[Evan]

If your carb sync is way out of whack, that can easily cause plug fouling as it's dumping more gas into that cyl compared to the rest.

Syncing the bike is not hard at all if you get the right tool. http://www.carbtune.com/

In fact a carbtune is cheaper than any dealer will charge you to do the job, and honestly you will tune it better than the dealer will. Most dealer mechanics are not perfectionists.

 

Good advice, in my opinion. I bought the carbtune, it is easy to use and it has sure paid for itself.

[Dano]

A carbtune may help this situation, as the #2 carb (front left, same as dark plug) is the carb that the other three are set to. If the others have been turned down, #2 is still high and the others need reset. See the instructions for carb synching, setting the vacuum on #1 (left rear) to the front one on left side (#2), move to the right side, set the back one and front one evenly then set them to the ones on the left (2 different screws). You'll need to see and read the instructions to get a better idea of how to do it tho.

 

You also need to check the plug cap, wire, coil etc. to make sure it's sending juice to the plug. Others will chime in here, I'll just bet.....

[Yammer Dan]

I'd Bet a sync and plug wires clears it up. But which one??