After racing motorcycles for 15 years, jetting was important and here is the way Pro racers jet a 4-stroke carburetor.
Warm up motor, then run at full throttle under load for approx. 2 min. Hit kill button. Take out spark plug and look to see if too rich or too lean. A rich carburetor will make the outer edge of the spark plug black, and a lean motor will make the plug look same a new [white or very light gray].
This test only checks the main jet and the object is to have a spark plug a medium brown.
Never do this test without a warm motor.
Best way to save money is to solder a jet close and use a number drill set to arrive at the correct opening.
If you are using the Honda GXH50 carburetor, the main jet is smaller than the HS 142A motor by 2 sizes.
A restriced intake breather will RICHEN the mixture not lean it as it acts like a choke. Less air more fuel.
A tuned exhaust on a 4 stroke WILL have a major influence on jetting, and normally leans out the mixture.
The HS142A motor has a much higher top speed than the Honda motor and all is because of the main jet in the carburetor [both use a 15 MM carburetor].
One of our test bikes has the Honda motor and uses a stock HS 142A carburetor [original main jet] with a tuned pipe and the jetting is 100% on the money at sea level.
Have fun,
Warm up motor, then run at full throttle under load for approx. 2 min. Hit kill button. Take out spark plug and look to see if too rich or too lean. A rich carburetor will make the outer edge of the spark plug black, and a lean motor will make the plug look same a new [white or very light gray].
This test only checks the main jet and the object is to have a spark plug a medium brown.
Never do this test without a warm motor.
Best way to save money is to solder a jet close and use a number drill set to arrive at the correct opening.
If you are using the Honda GXH50 carburetor, the main jet is smaller than the HS 142A motor by 2 sizes.
A restriced intake breather will RICHEN the mixture not lean it as it acts like a choke. Less air more fuel.
A tuned exhaust on a 4 stroke WILL have a major influence on jetting, and normally leans out the mixture.
The HS142A motor has a much higher top speed than the Honda motor and all is because of the main jet in the carburetor [both use a 15 MM carburetor].
One of our test bikes has the Honda motor and uses a stock HS 142A carburetor [original main jet] with a tuned pipe and the jetting is 100% on the money at sea level.
Have fun,