idle mixture screw does nothing

[Fishstick1962]

Hey guys:
I'm working on a 2005 90ELPTO OL114324.
It was idling rough a coughing a bit so I pulled the Carbs, cleaned them with Power Tune really good, Blew out all passages and re-installed them. Adjusted carbs with a vac gauge all was really sweet. Motor purred. Motor sat for a couple days and when I started it again it ran like sh**! Started going through the carb adjustments again and found that carb #3's idle mixture screw has no affect on the idle. Pulled carb and I think the carb base seal is bad. It is an O-Ring and doesn't have much "O" left in a few places. My experience says that if the mix screw does nothing then the base gasket is bad. What do ya'll think. Any input would be greatly appreciated.

 

[Texasmark]

Re: idle mixture screw does nothing

Agree. Since it sounds like you know what you are doing and didn't screw the screws in too tight and screw up the seal (which can do the same thing), then air coming in after the carb will definitely shunt the fuel air mix and do as you said.

But why did it take a couple of days of sitting to expose it? You'd think you'd have that problem right off.

Mark

 

[Chris1956]

Re: idle mixture screw does nothing

Fishstick, Amother possibility is that the cylinders that use that carb are not operating, due to ignition failure or some other issue. That would explain why after some days it started running poorly.

 

[Fishstick1962]

Re: idle mixture screw does nothing

Hey guys, thanks for the input.
Did a little more T/Sing today and ended up pulling the carbs off again. Started cleaning once more and found a jet hiding under a rubber stopper(for lack of a better word) that I missed before, turns out that this jet was very very dirty on the three carbs that where not acting right. I'm sure there was some loose trash in there. Haven't put back on yet. Will do that tomorrow and let yall know what I find out. Thanks again for the input.

 

[Fishstick1962]

Re: idle mixture screw does nothing

Got her back together and in the water. She runs GREAT! I can't believe I missed the other jet hiding under the rubber stopper. And a bit of info for others with this motor...you MUST have the air intake installed when syncing and adjusting the carbs. It ran me in circles until I put the air breather back on.
But all is well and she puuuurrrrrs!
Thank for the input guys.