carb idle jet question

[jy118lfd]

I have a 78 235 johnson and it runs fine at mid throttle and beyond. At idle it lean sneezes i have cleaned all the carbs and it is better I also replaced the low speed orfices with new factory sizes. The marina said sometimes you have to jet them up to get them to run better. My question is this how big do I go What is the increment to see a change in idle quality. .001 or .005 I dont know and dont want to go to big? Thanks In advance for the help

 

[WillyBWright]

Re: carb idle jet question

You're going to have to go smaller with the idle jets. You won't see much of a difference with .001. I'd go .002 smaller. The jets actually control air and not gas, so you have to go smaller with the air to draw more fuel. (That's if the idle jets are on the outside of those carbs. If they're inside and exposed to raw fuel, then the opposite is true.)

 

[jy118lfd]

Re: carb idle jet question

The Idle jets meter the fuel side not the air they are exposed to fuel. The carbs have idle air bleeds and someone prior to me owning opened them up. Causing the lean idle. I can not get smaller air bleeds cause they are part of the main body (discontinued)

 

[Dhadley]

Re: carb idle jet question

What exactly are you trying to change? The idle jets are indeed in the side of those carbs and meters fuel. There is a jet in the throat of the carb thats removable but its a pull-over jet, not an idle air bleed.

 

[jy118lfd]

Re: carb idle jet question

I am trying to change the idle mixture. The jets I Am trying to change are the ones in the main body behind the low speed orfice plugs according to the factory manual. The air bleeds I spoke about are in the throat of each barrel not the single pullover jet. The air bleeds are there to create a siphon so the fuel can be pulled out of the bowl. But it looks like they were clogged and someone stuck wire in them to clean them,now two of the carbs have larger holes than the top carb. If I partially choke the bottem carbs the lean sneeze goes away. My only real question is how much size difference do I need to go before I see a change in idle quality. .002 .005 ??