how many turns out?

how many turns out????

  • Total voters
    24
Bacchus

Bacchus

Senior Member
Supporting Member
Joined
Sep 11, 2007
Messages
3,174
Reaction score
7
Location
USA Arizona, Phoenix
to my understanding the "correct" baseline setting for the mixture screws located ont he bottom side of your carbs is 2.25-2.5 turns out. I ran a search to find this information and what I found after reading all the threads I could on this is that settings vary wildly... some guys post up 1.25 turns, others post up 2 turns, somebody says 4+ turns....

I figured a poll was in order to establish where the actual baseline realy is..

THIS IS MULTIPLE CHOICE, SO IF YOUR SETTING IS 2.75 FOR EXAMPLE, YOU SHOULD PICK 2.5 & 3.0
 
Last edited:
I'm at 3.5 Its too rich but helps cool it a little at slow speeds. (stoplight stuff) I'd rather run a little rich and have a happy healthy motor, might not amount to much but I feel better.
 
LOL

Seriously though. 2 1/8 turns out is where to start with per the factory manual. If running pods then try maybe lets say 2 3/4. Best to use some type of A/F meter to get these correct
 
here is an interesting observation on this subject for you guys....

I was working on a set of zl9 carbs yesterday, these carbs were torn down on the bench, when I re-assebled them I set the screws to 2.25 turns out, then I looked at the engine side of the carbs where the needle end of the screw sticks into the little hole and I noticed that although I had set all four to the exact same setting they were obviously not the same. I could tell by the amout of the needle visable through the hole.

I checked and reset...same result. so if I set them by "turns out" I did not have equally tuned carbs. I set them to be in the same position, which is with a small bit of needle visiable beyond the hole.

anybody got comments on this????????
 
Manufacturing tolerances / The turns out are the best method available for most people. It is not uncommon for me to run different main jets from 1 cylinder to another on snowmobiles though it does require extra work and effort.(testing/drilling) I have found that there are lots of things that affect mixtures such as coolant flow and will the inside cylinders run hotter than the outside? Inlet air distribution, air inlet temp can vary with pods, is one cylinder receiving a little different ram air effect, Does your compression vary some from cylinder to cylinder? etc. This is why I am a proponent of the Recordable EGT. Been using them for over 20 years on2 strokes/ 4strokes/ single cyl/ multi cylinder. I have used them on all our race vehicles...I just don't have the time or inclination to use them on a bike. If I ever build a race bike I will, but I'd rather be building a racing sled. Anytime you shove something up a tailpipe you are getting the overall reading not an individual reading from an individual cylinder.
 
Last edited:
i personally feel vacuum gauges are the most reliable way to set the correct idle mixture .more complicated on four individual carbs each running its own cylinder. setting the idle to the desired speed, then tuning each mixture screw to acheive the highest vacuum at that idle speed. this co-insides with syncing the carbs.i like to get these the best i can(usually repeating these steps several times until no more gain is acheived).this can usually be verified by turning each screw in an eighth of a turn and seeing the idle speed drop a little. once all thats done i like to put another eighth turn out on the mixture screws to make sure it "pops right off" when you hit the start button once its warmed up a little. there is a certian amount of "feel" that comes with the experience of doing it a few times, for instance poping from the exhaust on deceleration is a sure sign of a lean idle mixture. don't know if this helps or you guys think i'm full of it, this method is tried and true for me and i have tuned multiple carbs on various machines and the people are always very pleased with improved drivability and low end throttle response. my zl900 will pull 6th gear at less than 2000 rpm (pretty flat ground) i like it this way so it doesn't spin the tire so bad on the crappy gravel road i live on. by the way my screws are at about two and ahalf with pods and no mufflers on other wise stock exhuast. man i hate typing!
 
:iamwithstupid: Din't actually mean stupid but can't find the "yeah that" sign so this works...gotta admit though it is kinda funny...another good way to skin a cat.
 
wish i had access to the EGT set up you spoke of lowlife, i think that would be a nice addition to my tool box for tuning purposes,understand the way it works just have no experience with it. you do multi-cylinder 2 strokes in your sleds? i have done lots of Jet-Ski work over the years and believe them to be similar, may have to get on that subject one day,different thread maybe.
 
If they have never been adjusted, you will not see them - they are covered by little inserts (first pic) - drill a hole - carefully - put a hook or self tapping screw in them and pull them out. Then you will see the little brass screw (2nd pic). These are on the bottom, front of each carb. Later.
 

Attachments

  • 06140909521.jpg
    06140909521.jpg
    37.3 KB · Views: 31
  • 0614091005a.jpg
    0614091005a.jpg
    37.2 KB · Views: 33
Jarney said:
If they have never been adjusted, you will not see them - they are covered by little inserts (first pic) - drill a hole - carefully - put a hook or self tapping screw in them and pull them out. Then you will see the little brass screw (2nd pic). These are on the bottom, front of each carb. Later.
Click to expand...

Thanks jarney. That was really helpful :thumbsup:
 
I'm so glad Blag was willing to ask that! It was a great mystery to me 'till couple of years back, had to look at someone elses bike to figure out why I didnt have any adjuster screws on mine!!
 
zot said:
I'm so glad Blag was willing to ask that! It was a great mystery to me 'till couple of years back, had to look at someone elses bike to figure out why I didnt have any adjuster screws on mine!!
Click to expand...

You wouldn't mind, I stripped the carbs down completely in 2008. Ya think I'd have remembered whats what.... :roll:

I am so glad I asked a few dumb questions about the carbs... My god, the bike is running sweeter than I can ever remember!! She's always been a little rough at idle, as long as I've owned her. I spent a couple of hours dialling her in and man, she's like a new bike!! And all for a little tuning.

I'll be going to a fund raising "dyno day" this weekend, I might put her up and see what she's making....:devil:
 
Blagadán said:
You wouldn't mind, I stripped the carbs down completely in 2008. Ya think I'd have remembered whats what.... :roll:

I am so glad I asked a few dumb questions about the carbs... My god, the bike is running sweeter than I can ever remember!! She's always been a little rough at idle, as long as I've owned her. I spent a couple of hours dialling her in and man, she's like a new bike!! And all for a little tuning.

I'll be going to a fund raising "dyno day" this weekend, I might put her up and see what she's making....:devil:
Click to expand...
Cool! Get that dyno data!! it will be the first for a 750!
 
Bacchus said:
here is an interesting observation on this subject for you guys....

I was working on a set of zl9 carbs yesterday, these carbs were torn down on the bench, when I re-assebled them I set the screws to 2.25 turns out, then I looked at the engine side of the carbs where the needle end of the screw sticks into the little hole and I noticed that although I had set all four to the exact same setting they were obviously not the same. I could tell by the amout of the needle visable through the hole.

I checked and reset...same result. so if I set them by "turns out" I did not have equally tuned carbs. I set them to be in the same position, which is with a small bit of needle visiable beyond the hole.

anybody got comments on this????????
Click to expand...

It sounds like its just a manufacturing difference. Turns out would still be the same per carb, its just that the seat which the needles pressing against isnt drilled as far down (upside down) on the ones you cant see as easily.
 
You must log in or register to reply here.
Back
Top