Cylinder 3 running rich

[CLYNT BEASTWOOD]

My #3 cylinder is running rich but 1,2,4 seem fine. Any thoughts? Oh it's an 89 750

The plug gets sooty black after about an hour of riding.

I know the carbs need synced but would that cause one cylinder to run lean?

[92xjunker]

Couple. Float needle worn, debris stuck in it or sticking. Float height maybe off, loose fitting float (worn or torn O-ring/seal) or a bad plug or plug wire. I'd include worn jets but, usually they wear out together.

[CLYNT BEASTWOOD]

Well, I just replaced the o-rings in the carbs a few months ago, I had a problem with the float needle in carb 1 being stuck. I checked and cleaned the other float needles from any debris at that time. I have 02 gsxr COP's how can I check to see if that particular coil is firing?

Duh, I guess I just pull the plug and see if I get spark like normal

[92xjunker]

Same procedure as a standard test, just use the COP as the wire. FYI you'll have to tape the plug in the COP. Safety first, if the plunge falls out during testing you will feel if it works...

[CLYNT BEASTWOOD]

The bike runs incredible and pulls like hell through all the gears but when it warms up it lags a bit off the line, due to the plug foul I would guess

Got ya, I don't need to feel if it works, safety first.

[92xjunker]

You may want to turn the A/F screw back a little to see if it's a mixture issue. Better yet, do the drop down adjustment on them. The procedure is in the WIKI.

[CLYNT BEASTWOOD]

Ok, I'll check it out in the morning

Hey, junker, I'm unfamiliar with the wiki, what article is it under?

[arsenic]

Are you using Mikuni main jets or DynoJet main jets? What specific jetting? I don't know dick about the wiki either, sorry man. I have a basic understanding of how the drop down method works, and I think it's a waste of time and energy. I'm betting it's a main jet issue more than a mixture issue. What are the A/F screws currently set at?

[CLYNT BEASTWOOD]

I'm using Mikuni main jets. My A/F screws are all currently set a 2.5 turns out.

[arsenic]

What needles? What size main jets?

[CLYNT BEASTWOOD]

Stock

[arsenic]

So, basically you have no idea what size they are? If you look and realize that 1, 2 & 4 are 105 and #3 is 110. That's not the problem. They are supposed to be that way.

[CLYNT BEASTWOOD]

No, basically I don't. I was trying to avoid taking the carbs back off, if at all possible. Thanks for the info

Why would it be different on carb 3?

[arsenic]

Why would it be different on carb 3?

I couldn't tell you what the engineers reasoning for that is, but I know I'm not smarter than them. I'm guessing there is a valid reason.

[CLYNT BEASTWOOD]

Ok, thank you, arsenic