2000 50 hp johnson running on one cylinder

[Craigd51]

engine running on lower cylinder only, verified spark, timing, and compression, inspected reeds, did sync on carb linkage, carbs spotless, no fuel system leaks, found that if I disconnect linkage between carbs and crack butterfly on top carb that cylinder will fire, as soon it goes to full closed the cylinder drops out, d? I have a vacuum leak somewhere that I am missing, could that be causing not enough vacuum to be pulled through carb to correctly open the reeds, there is no lean sneezing condition what so ever, I did the old can a 2 plus 2 around the intake and carb flanges and no success, sprayed carb cleaner directly into carb throat and it wont fire. only way it will fire is if I crack the butterfly.

 

[boobie]

Sounds like an idle circuit is clogged in the carb. JMO.

 

[ob]

What does the top plug look like after the cylinder drops out as you put it? Does it appear wet with fuel mix? Did you insure that the air metering orifice at the top of #1 carburetor is completely clear. You mentioned that the carbs were spotless. I'm curious where you set the low speed/ idle mix screws on each carburetor.

 

[Craigd51]

Low speed screw is set same as bottom at 3 to 4 turns out, if i open it more that cylinder does nothing, air jet in the top of the carb is also clear, i replaced the gasket also under the plastic cover on top the carb as was well, if i spray that cylinder with raw gas when the engine is running it does nothing, habe to physically mpve the butteryfly for it to fire, just barely crack it

 

[Craigd51]

I also turned the mixture screw back in to lean it out and it did nothing

 

[Craigd51]

Got the issue taken care of, pulled top carb snd verifed idle circuits were clean, reinstalled carb and synced the linkage again, found upper carb causing rich condition, leaned out mixture screw and she came to life