turn mixture screw which way to lean out?

[rinaldi]

My sons 90 DRX I believe is running a little rich. Turn the screw counter clockwise or clockwise to lean it out a bit?

[Logan #34's Dad]

Counter-Clockwise will lean ya a little. Giving you a little more air. I'd just change the main jet to the next lower number.

PLEASE someone correct me if I'm wrong! It can get confusing.

[hotquads1]

Rocky is right , out is leaner, but this affects the low rpm curcuit the most idle to 1/4 throttle, needle clip for midrange , main jet for WOT. you must determine where in the throttle position you are rich.
marc

[TeamNeilson]

I don't know if this helps, but for me, I use the following chart to help me figure out where the adjustments need to be made.

Basically you figure out where on the throttle you are having the issue, then you use the chart to figure out what part of the carb is responsible for that action and adjust accordingly.

The ones, that I use at the track are "Air Screw", "Clip Position", "Needle Taper", and "Main Jet". The others, I ignore..

http://chris.neilson.googlepages.com/CarbCalibrationChart.png

[Logan #34's Dad]

Hey Neilson, How do you know is the needle taper is right? I'm guessing that if I run out of clip positions then I need a different needle?

[TeamNeilson]

I find if I can't get the motor to behave at the mid throttle position (the motor still bobbles at half throttle), and i've gone through all the clip positions, then ya, i'll move to a new needle.


The absolute most important thing for me is documentation. Everything you try should be written down and noted in case a certain combination gets you better than you had before (or worse). This also helps if you get stuck and can't figure out the problem, pasting the notes here, or relaying the info to your favorite tuner will get you back to the way you need it quickly.

I've got a little black book that is chock full of notes. Every track has a 'section'. (oh goodness, don't get me started on my 'black book'. hahah)

[skyeryder]

got a question along this same thought... his 50cc pipe broke at the head tonight so I had a two piece 90cc pipe in the waiting that we put on, now we lost alot of low end, but once he gets 3/4 throttle in the pipe it flys. So my question is will the air screw help that much or do we need to rejet or port&polish or ..... Anyone that has put a 90 pipe on a 50 your help is appreciated to get us pointed in the right direction.

Everyone is in Virginia so it's gonna be hard to get parts:(

[mudder700]

I bought two different pipes supposebly for a 50cc quad, when matched up to our 90cc pipe, they are identical, either I was sold two 90cc pipes or they are the same from DRR, might need to just rejet to get to run properly, I was originally told it wouldn't work putting a 90 pipe on a 50, but found that to be untrue, we ran all last year and won a championship with it on our DRR50, anyone looking for pipes contact me, they are going to be sold cheap as we don't need them anymore.

[skyeryder]

ours is the new style 90 pipe it's two piece the expansion chamber is alot further forward. top end and idle it's great, but right now we'd be dead last on a holeshot,

[hotquads1]

I think clutching will be your fix, little less roller weight and give it a try.
marc

[skyeryder]

It took the 4 gr out and put the stock 3.5 back in it helped but it won't even turn the tires over in gravel

[hotquads1]

higher rpm shoe engagement could help , (3 little springs), if it ran long with the broken headpipe you should do a compression check and verify it is good, it suck dirt in just a few seconds with a broken pipe. also which carb is it ?

[bulldogfallon]

His torque spring is weak...the belt is dropping before the clutch is engaging which is hard for the 50 with the 90 pipe to over come.

A fresh spring should at least make the tuning job more accurate.

Right now the torque spring is skewing all the tinkering....