Kind of confused on jetting. 3/4 turn on the air screw? Ktm 144

So Im a little stumped on jetting my bike. My bike is a 2008 ktm 144 and I am running a 45 pilot and a 202 main jet with the stock needle on the third clip position with the air screw 3/4 turn from closed. My bike has low end bog with no power down low compared to my friends ktm 125. Now 3/4 of a turn is too lean I assume and I should drop the pilot down a size? BTW my elevation is 520ft above sea level and I am running the bike at 75 degree and above.

You need a BIGGER pilot jet to richen it up, like a 45. Opening the air screw leans it out and screwing it in richens.

You need a BIGGER pilot jet to richen it up, like a 45. Opening the air screw leans it out and screwing it in richens.

Wow I had that wrong, so I should jump up to a 48? thanks a lot btw

yup, you need a larger pilot.

the airscrew preferrably to be between 1.5 - 2 turns out.

So yes on the 48?

Here is the jetting I had in my 2008 144:

202 M

45 P

#6 slide

R1470D 4th clip

The bike new had a very bad off idle bog. I would crank the air screw in and see how it runs before you do anything else. Don't be scared to crank that air screw all the way in.



PG.42 = 144sx jetting chart.


79° - 98°

AS - 1.5

IJ - 45

Needle - R1471H

POS - 3

MJ - 202

I used this manual to find the jetting thats in my bike in the first place. Thanks though.

Why are you running your AS at .75 of a turn instead of the 1.5 that the chart says?

I run the jetting chart specs in my 2011 150sx and it runs great. If I am at home I live at 62'. If I am riding in Nevada I run the specs for 4500'.

Last weekend my son won back to back motos on the 150 in his class at Fernley (4500' @70°). The bike is stock with the exception of having a 50T rear sprocket on it.

I run pump gas (91) with Golden Spectro at 52:1.

Have you looked at your plug to read the color? Do you have soot or spooge coming out the exhaust? Is your float level right?

I was only able to get rid of the bog by turning the air screw in to .75 turns.

I originally set it to 1.5 turns and it was horrid.

I run 93 pump with mogul 800 at 40/1.

I plugged the plug and it looked perfect.

No spooge as well.

And yes my float height is correct, I did what the manual said to do (45 degree angle etc.)

I bought a 48 pilot and am putting that in today to see if that helps

Other things to look for are an air leak, broken or cracked reed, bad crank seal on the dry side.

Good luck.

Other things to look for are an air leak, broken or cracked reed, bad crank seal on the dry side.

Good luck.

thanks Larry appreciate everything

Mabe your exhaust valve is stuck open?

Mabe your exhaust valve is stuck open?

tearing apart my bike tonight, thought this may be the culprit as well

There is an inspection window on left side of cylinder with vent tube attached to it. Take off cover, mark on right should move down when you rev the bike if it is working. There is two horizontal marks. Left is stationary, right moves down as exhaust valve opens.

Before you tear everything apart, did this happen like over night?

The pj gets easily plugged with the crap ethanol gas [brown sludge]. Take it out and clean, shoot some brake cleaner up the pj hole in the carb when the pj is out.

Despite what everyone says including the manual there is no set position for the a/s. It has to be where it NEEDS to be for the conditions. The manual just gives a STARTING position. It's a SCREW FOR A REASON.

With a hot engine and the bike on the stand whack the throttle open. If there is any hesitation turn the a/s in by 1/8 turn and try again. Start at 1.5 out. Allow about 10 seconds between tests for the crankcase to clear and try again. Keep turning in until there is no hesitiation. If you are less than 1 turn out go to the next larger size pj and tune again. If you get no hesitation starting at 1.5 out turn out by 1/8 turn until you do get a hesitation. If your out 2.5 or more go a step smaller on the pj and tune again.

bike is running beautifully with the 48 pilot jet, when it gets a little hotter out I may throw the 45 back in. Bike really screams and makes good power. Last lap or so of practice the bike felt a tad down on power so I am going to perform a compression test, Anyone know what psi it should kick cold and hot? Here's some eye candy as well. :ride:


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now