Carb Tuning Skinny Plz...

Yamah0

Yamah0

XFT
Location
Dubai
Hey peeps.. Im trying to tune my single 49mm and been messing with different jetting but i kind get lost at times and just call it quits till the next time.. i know it needs patience which i dont have most of the time!

Whats the best way/trick to tune a carb?
How do you know that.. ok these jets are perfect?
Lean and rich... whats the exact charastaristics of both?

Right now i have 135high, 125low, 2.3NS and 115 spring and what i was doing was i open top srew 2 turns out and low 2 turns out and started by closing on the low till it hits nice.. at least that was the plan but it was sort of hitting but not clean and clear, so i kept opening and closing till i got bored and went home:biggrin:

What should i do?

Thanx in advance:biggthumpup:
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
drop your 2.3 to a 2.0 and try that......... you are on the right track on adjusting.......... sounds like as you turn the low speed in, it getting better, but you may be running too much fuel through it........
 
keefer

keefer

T1
Location
Tennessee
What is your pop off pressure set to? If you drop the N/S to 2.0 it will raise the pop off thus leaning out the 1/4 to mid a little. Check it and start around 22 lbs.by changing the spring. If you are running high compression then the signal to the carb will be strong and make the low end a little more picky but with a 49mm you should be able to get it right. Sounds like you are on the right track. Call Paul at Jr Magoos and he can give you a more experienced direction on the best combination to start with and tuning. He has helped me big time with my setup.
 
Yamah0

Yamah0

XFT
Location
Dubai
Thanx for the replys...

So when asked what is your pop off set to... Does that mean what spring are u using, or
is there a way to controll and play around with pop off without changing the spring?

So does everyone think i definetly should swap to a 2.0?
What pop off should i be aiming for?

In a couple hours im going to get to it again.. hopefully it comes along nice this time. We'll see.

Thanx again:biggthumpup:
 
Last edited:
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
The springs will get you in the ball park and are one measure of popoff, though it's just a rough indication.

Ideally, you'll want to measure popoff with a popoff gauge, in pound per square inch (PSI).
Mikuni makes em...Paul sells em. Though I am sure you could make your own.
Anyhow...you measure your popoff, and then finetune it by changing springs or bending tabs on the spring pivot lever.
 
S

sflsurfrider

im running a single 48 mikuni with a stock flame arrestor and my settings are:

135 hi
125 lo
32 lbs popoff
both adjustors at 1 turn out.

it hits very clean on the bottom w/o any dead spots up the range.
 
S

sflsurfrider

i cant remember.... i know the n&s + whatever spring i used gave me 32 lbs popoff

question:

is there a difference between using a 1.5 n&s and whatever spring to achieve a given popoff VS using, say, a 2.0 n&s and a different size spring to achieve the same popoff? i mean, 32 lbs is 32 lbs. right?
 
Takeastand SJ

Takeastand SJ

R.I.P. 8/9/2008
Location
Washington
I am guessing you have a full spectrum, they do not work like mikunis or other carbs. The fuel circuits are way different, I would contact full spectrum for advise if you are new to tuning carbs. I have a 48mm powerbomb low 150 high 155 2.0 n/s with a 85 return line restrictor.
 
Yamah0

Yamah0

XFT
Location
Dubai
My setup is all in my signature Peeps!

Anyways six million curses five thousand head smacks few kicks here and there and a bunch of screwdrivers thrown left and right i finally got to something and i would say its 70% there..

I ended up with a 142.5 high, 127.5 Low, 2.0NS and a 95 spring which is what i had.. i wanted to try a 140 but didnt have one... anyways basically when i hit full throttle it doesnt go BRAAAAAAAAAAAP and hit hard right from the begining... it takes a sec aor two then hits..

If im at half throttle then hit the throttle full.. the punch feels better but theres still that second delay.

In other words also... if im at around idle and keep hitting full throttle on and off quickly, the punch wont come on unless i keep the throttle punched in for a sec or so.

Long story short, im still not happy with it:(

So what does this sound like? rich, lean, buy dual carbs or a different motor?

Tomorrow im taking my ski to this mechanic here thats supposedly the man that knows carbs... so we'll see what he'll do.

I'll keep u posted!

Thanx
Zane...
 
Takeastand SJ

Takeastand SJ

R.I.P. 8/9/2008
Location
Washington
Yamah0 said:
My setup is all in my signature Peeps!

Anyways six million curses five thousand head smacks few kicks here and there and a bunch of screwdrivers thrown left and right i finally got to something and i would say its 70% there..

I ended up with a 142.5 high, 127.5 Low, 2.0NS and a 95 spring which is what i had.. i wanted to try a 140 but didnt have one... anyways basically when i hit full throttle it doesnt go BRAAAAAAAAAAAP and hit hard right from the begining... it takes a sec aor two then hits..

If im at half throttle then hit the throttle full.. the punch feels better but theres still that second delay.

In other words also... if im at around idle and keep hitting full throttle on and off quickly, the punch wont come on unless i keep the throttle punched in for a sec or so.

Long story short, im still not happy with it:(

So what does this sound like? rich, lean, buy dual carbs or a different motor?

Tomorrow im taking my ski to this mechanic here thats supposedly the man that knows carbs... so we'll see what he'll do.

I'll keep u posted!

Thanx
Zane...
Click to expand...

You need to raise your low jet way up and it sounds like your high is still lean also, but I would concentrate on the low first. You also need a restrictor in the fuel return line. Unless the mechanic knows how to tune full spectrums it is useless to bring it to him, contact full spectrum for advise.
 
Yamah0

Yamah0

XFT
Location
Dubai
Ya im running a 60 restrictor in the return.

I forgot to mention that my pop off with that setup was 23psi... does that sound right?

That mechanic knows FS.. We'll see
 
Yamah0

Yamah0

XFT
Location
Dubai
Ok well i took it to that mechanic i told u about, he put a 135high 140Low
95Spring and 2.0NS... the ski feels much better but that delay in the very begining is still there... maybe for a lot of people this might be ok but me being so picky i dont like that one second delay.
Im also thinking maybe thats just the way it is and im expecting more out of it.

Now the guy said that it could be my impeller... but i dont think so. Im running an impros concord 13/15 3mm cutback... he said to try my previous 12/17 skatrak... what do u guys think?

Another issue that might tell us something is when im doing the power 360 turn, the ski will become sluggish in the middle of the trick and basically ends the turn feeling boggish with me having to blip to clear out.

ummm.....:banghead:
 
Takeastand SJ

Takeastand SJ

R.I.P. 8/9/2008
Location
Washington
If your motor "delays" for 1 second from 0 throttle it's probobally not getting enough gas. Either your popoff is too high or your low speed jet needs to be bigger. Try opening your low adjuster more and see if that helps.
 
SuperJETT

SuperJETT

So long and thanks for all the fish
Location
none
This is very hard to describe if you don't know which is which.

Hesitation - ski is lean, not enough fuel, when you hit the gas it starves for a second and rpms will drop, then it goes. If you are super lean, it will actually die.

Loaded up - ski is rich, too much fuel, when you hit the gas it will climb in rpms but slowly until it clears out and takes off.

Pop off does the same thing, however it's more of an immediate thing at very low rpms. If it's too high, the needle doesn't open as quickly as it should. If it's too low, it's too far open.

Idle speed and mixture is controlled by the idle stop screw and low speed screw. This is the very first thing you should adjust. If you ride the ski to get it warmed up, then let off the gas, it should go down to idle and basically idle forever. If it doesn't, you need to start there.

Next I check for idle response, let it idle for 45-60 seconds, then blip the gas to like 1/4 throttle. It should yank. If it dies, your idle is too low, if it's sluggish, you're too rich. I check it by going further in the direction I think I am. If I think I'm lean, I close the low screw(s) another 1/4 turn and verify that made it worse and vice versa.

Then we go to popoff. You can generally get it in the ballpark by going around 25-35 psi. I set it, ride it, then raise it the next step up and see if that leaned out the response. This is more of a transition thing you check by riding at low rpms and blipping the gas at different rpms. It's hard to tell if you're too rich, but very obvious if it's too high because it will hesitate again and if it's way too high the ski will never rev up and just run on the low speed circuitry.

Next is low jet. Ride at 1/4 throttle for a good minute, then pin it. Same checks, hesitation = low jet too small, loaded up = too big.

Then same thing for the high jet but at like 2/3-3/4 throttle. Good luck.
 
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