Hey guys, I've searched the forums and I'm still having trouble so I'm hoping someone can help me out.


Some background: I'm working on a neighbor's 2005 ZRX1200R that had a leaking fuel petcock about 3 years ago and so he just parked it and let it sit. He tried some things to get it running again before I took over and gave it a shot.


What I've done/checked so far:

• Replaced the fuel petcock and main fuel line (no more leak now)
  
• cleaned the carb and jets several times. I don't know if I could make them any cleaner. I haven't gone the carb rebuild kit path yet.
  
• checked the floats and confirmed they're all in tolerance.
  
• set the fuel/air mix needle at 2.5 turns out.
  

So after all this the bike idles really well but seems to bog due to being rich when you rev it. it also emits black smoke from the exhaust, i believe due to rich mixture. The spark plugs are also turning black which also leads me to think its too rich.


I have tried turning the fuel/air mix needle ALL THE WAY IN to see what happened, thinking it wouldn't idle. It idled just fine. I was confused.


I have noticed that I can see fuel entering the carbs via the main jet (where the needle drops into and lifts up with throttle input. My expectation is that no fuel should be coming through this jet at idle, and yet it does. So I turned the idle down as low as it could go and it's still pulling fuel through that main jet.


My gut says to lean it out but I don't know how to beyond what I've already tried. as far as I know they are stock jets too...


Any ideas guys? I've been all through the manual and just can't figure it out.


Any suggestions would be greatly appreciated!

 

2 to 2,5 Turns out is about right.
From your description it sounds like the Carbs are flooding on 1 or more cylinders so maybe time for the rebuild kit as I suspect the Float Valves have gone hard and not making a good seal with their respective seats.
Or your Float heights are set wrong despite you saying they are.