carb tune question

[K85 Octane]

I don't know what this screw is called but I read it's for the off idle performance. I turned the adjusting screw 2 full turns counterclockwise in an effort to richen this circuit. I didn't feel anything noticeable when I drove it afterwords, and my A/F gauge didn't either.

Do I turn this IN to richen or OUT? If I'm all the way out already, this needs a new jet and start from the beginning huh?
The screw is located under the gasket on my current carb. This is a picture of my old carb which doesn't have access to this screw.

 

[K85 Octane]

Also, how do I richen the entire carb up without changing jets. I'm just looking to fatten up everything BUT idle, and then go from there.

Thank you

 

[4X4HIGH]

Also, how do I richen the entire carb up without changing jets. I'm just looking to fatten up everything BUT idle, and then go from there.

Thank you

The ONLY real way to make the mixture richer is to change to a larger jet OR decrease the amount of air that can enter through the carb (impossible to do). So looks like you're changing jets or leaving it alone.

 

[K85 Octane]

I guess I need to specify

I'm just looking to get it as rich as possible so I can drive it to a couple places. It's too lean right now. One of the places will be the dumbass carb guy I'm working with. He hasn't changed any jets yet, just likes to turn things and say "try it". He has a whole draw full of Qjet needles and jets.

So, I'm just looking to richen it up as much as possible temporarily. The screw I'm talking about in the picture is all the way out. I feel no resistance turning it, it's wobbly, but can't be pulled out.

 

[scottsdale86]

You are referring to the APT and it is ONLY used at part throttle or during highway driving. It needs to be two turns out. Its not made to richen things up like the idle mix screws are. Here is some great info I recommend reading it all its worth it. http://www.73-87.com/7387garage/drivetrain/myqjet.htm and this http://www.cliffshighperformance.com/tech_qjet_history_1.html
Doug Roe makes a great book too http://www.amazon.com/Rebuild-Modify-Rochester-Quadrajet-Carburetors/dp/1932494189

 

[K85 Octane]

I started pulling my '85 electronic carb apart and noticed the secondary metering rods and hanger are different from my late '70s carb I'm currently using.

'85 hanger = T
'70s hanger = O

According to Doug's book, hanger T is a richer hanger than O, because it puts the metering rods FURTHER down into the orifice. I can't wrap my mind around that. Everything I know about dirtbike carbs and properly setting them up has no bearing on Qjets.

I thought my '85 just came in handy offering up a richer hanger, cause I thought the more you pull the rods out, the more fuel comes out. The metering rods from the '85 are fat and slow tapered. The '70s carb has a longer/ thinner tip on it's metering rod.

Page 133, paragraph 3, line 6-7 for reference. Is this a typo?

"lean (0.520 in), average (0.570), and rich (0.615)."
smaller the number = rod pulled out further

 

[K85 Octane]

also, if I find the two "part throttle" screws to be the same between carbs, can they be interchanged? How can I tell if one is more "rich" than the other?

still trying to read the book, I guess I just need to continue breaking down my unused '85 carb to really get a grasp on things.

 

[K85 Octane]

hmm, doing some more reading and investigations. How many other people have this book? Seems everyone swears by it but Qjets still remain a bad topic among the boards.

seems these metering rods that are held up by the hanger are really "air bleeds". They are exposed to the open air inside the filter housing. Seems the more you cover them up, the less air is mixed with the fuel inside the carb BEFORE it exists into the barrels. So, a fatter metering rod and lower hanger actually makes for a richer mixture. Ok, but there are a thousand other things at work that should be looked at too. Seems there are more "air" jets than there are "fuel" jets. Damn