motoz/HMF
06-21-2004, 04:20 PM
ALL new machines both on and off road must pass EPA emissions tests.
BEFORE you do ANYTHING involving jetting or tuning do this FIRST.
You need to set the fuel screw (on the bottom of the carb between the float bowl and the intake manifold) which is usually up in a tube cast into the carb body. You will need a narrow flat blade screw driver to do this.
Some people have been just going "3 turns out" or something like that..
You need to bottom the screw (lightly don't crank it down, you'll ruin it) and while the machine is running (it should be warmed up) turn it out from bottomed out to where you get the HIGHEST SMOOTH idle. It will get hi idle then start to get rough..turn it back in until it is smooth. Then set your regular idle to where you like it.
Adjusting the fuel screw will also tell you if you are too rich or lean in the pilot jet. OUT will RICHEN the mixture and IN will LEAN the mixture.
EXAMPLE: If you are at approx. 3.5 turns out from bottomed on the fuel screw this means that the adjustability of the fuel screw is at it's maximum (it will unscrew completely at approx. 5.0 turns out), you will need to go RICHER on the pilot jet.
If you are 1.5 turns out on the fuel screw that means you are at it's minimum (almost bottomed out), this means you are too RICH on the pilot jet and need lean out the pilot jet.
IF you do change the pilot jet to a different size be sure to RE SET the fuel screw to its highest smooth idle then set the regular idle screw to where you like it.
You should also re set the fuel screw whenever the temperature or humidity change. (say 90 degrees one day and 55 the next)
On the TOP end of the RPM range if things seem to be running bad DO THIS FIRST.
Get up to the RPM area where you think things are running bad and hold the throttle at a constant position, let the engine settle into that RPM then slowly back off the throttle...if the RPM seems to pick up and the machine runs better you are too LEAN and need to richen the main jet.
OR you can (while keeping the trouble RPM steady) pull the choke, if things get BETTER you are too LEAN and need to richen the mixture, if it gets WORSE you are too RICH and need to lean the mixture.
sO, don't get all flustered when you add a pipe or filter and it won't run. Do the above and you'll be on the right track
In MOST cases (because of that EPA static emissions test) you will be LEAN on both the fuel screw AND pilot jet.
Remember rich is good lean is bad.
Welcome to the world of high performance !
BEFORE you do ANYTHING involving jetting or tuning do this FIRST.
You need to set the fuel screw (on the bottom of the carb between the float bowl and the intake manifold) which is usually up in a tube cast into the carb body. You will need a narrow flat blade screw driver to do this.
Some people have been just going "3 turns out" or something like that..
You need to bottom the screw (lightly don't crank it down, you'll ruin it) and while the machine is running (it should be warmed up) turn it out from bottomed out to where you get the HIGHEST SMOOTH idle. It will get hi idle then start to get rough..turn it back in until it is smooth. Then set your regular idle to where you like it.
Adjusting the fuel screw will also tell you if you are too rich or lean in the pilot jet. OUT will RICHEN the mixture and IN will LEAN the mixture.
EXAMPLE: If you are at approx. 3.5 turns out from bottomed on the fuel screw this means that the adjustability of the fuel screw is at it's maximum (it will unscrew completely at approx. 5.0 turns out), you will need to go RICHER on the pilot jet.
If you are 1.5 turns out on the fuel screw that means you are at it's minimum (almost bottomed out), this means you are too RICH on the pilot jet and need lean out the pilot jet.
IF you do change the pilot jet to a different size be sure to RE SET the fuel screw to its highest smooth idle then set the regular idle screw to where you like it.
You should also re set the fuel screw whenever the temperature or humidity change. (say 90 degrees one day and 55 the next)
On the TOP end of the RPM range if things seem to be running bad DO THIS FIRST.
Get up to the RPM area where you think things are running bad and hold the throttle at a constant position, let the engine settle into that RPM then slowly back off the throttle...if the RPM seems to pick up and the machine runs better you are too LEAN and need to richen the main jet.
OR you can (while keeping the trouble RPM steady) pull the choke, if things get BETTER you are too LEAN and need to richen the mixture, if it gets WORSE you are too RICH and need to lean the mixture.
sO, don't get all flustered when you add a pipe or filter and it won't run. Do the above and you'll be on the right track
In MOST cases (because of that EPA static emissions test) you will be LEAN on both the fuel screw AND pilot jet.
Remember rich is good lean is bad.
Welcome to the world of high performance !