KF GY6 150cc carburetor

Reveeen · 11-27-2009, 05:54 AM

Otherwise known as the PD24J.

I bought 2 brand new ones (from GIO), both came with a 103 main jet, some tuning info:

Main jet sizing at sea level:
With UNI filter 120-125
With UNI filter and low restriction exhaust 130-135

Test procedure:
1. Run engine at less than half throttle a minimum of 15 minutes to close electric choke
2. On a 300' or 100 meter stretch or greater, run the engine at wide open throttle
3. While still holding it wide open, cut the ignition (this is called a "plug chop")
4. Remove the spark plug and inspect end for color
a. White - Increase jet size
b. Tan/Brown - Correct jet size
c. Black - Decrease jet size

Hints:
1. Change jet size by 2 or 2.5 for fine adjustment by 5 for coarse adjustment
2. Reduce jet size by 2 or 2.5 for every 1500 ft or 500 meters of elevation
3. Stock fuel delivery may not be sufficient above a 130 main jet and may require larger diameter fuel lines and less restrictive fuel filter
4. Once main jet is selected, the air/fuel mixture screw can be adjusted for optimum idle

Mostly stolen from here:
http://www.buggydepot.com/buggy-tech...-rejetting/18/

Note:
The fuel bowl is sealed with a formed "O" ring, once removed it will no longer fit, running hot tap water over the O ring and stretching slightly between your fingers will "grow" it enough to fit "like a new one".

EDIT:
A #56 drill is "near as dammitt to a 127 jet

Weldangrind · 11-27-2009, 10:52 AM

Thanks for the info. My daughter's 150 Monster has a top end hiccup that could be described as a surge. I was thinking that the main jet was too fat at 120, but now I think it's too lean. I'm gonna buy more jets and see how it performs, since it has a Uni and a performance exhaust.

Reveeen · 11-27-2009, 03:03 PM

There have been reports of the intake manifold cracking, due to vibration, and the unsupported condition the carb is left in with the stock air box removal. So keep your eyes peeled.
The so-called "heavy duty" manifolds
http://www.partsforscooters.com/169-...category=74091
ALL seem to be aimed towards the mounting of a 30mm carb.

Weldangrind · 11-27-2009, 07:03 PM

10-4. I'll check to see if the manifold is loose or cracked at my next opportunity. I added some ABS as an extension so that the Uni could be placed under the seat; that could pose a bigger problem.

Thanks!

11-27-2009, 05:54 AM	#1
Reveeen Join Date: Jun 2009 Location: orbital platform Posts: 741	KF GY6 150cc carburetor Otherwise known as the PD24J. I bought 2 brand new ones (from GIO), both came with a 103 main jet, some tuning info: Main jet sizing at sea level: With UNI filter 120-125 With UNI filter and low restriction exhaust 130-135 Test procedure: 1. Run engine at less than half throttle a minimum of 15 minutes to close electric choke 2. On a 300' or 100 meter stretch or greater, run the engine at wide open throttle 3. While still holding it wide open, cut the ignition (this is called a "plug chop") 4. Remove the spark plug and inspect end for color a. White - Increase jet size b. Tan/Brown - Correct jet size c. Black - Decrease jet size Hints: 1. Change jet size by 2 or 2.5 for fine adjustment by 5 for coarse adjustment 2. Reduce jet size by 2 or 2.5 for every 1500 ft or 500 meters of elevation 3. Stock fuel delivery may not be sufficient above a 130 main jet and may require larger diameter fuel lines and less restrictive fuel filter 4. Once main jet is selected, the air/fuel mixture screw can be adjusted for optimum idle Mostly stolen from here: http://www.buggydepot.com/buggy-tech...-rejetting/18/ Note: The fuel bowl is sealed with a formed "O" ring, once removed it will no longer fit, running hot tap water over the O ring and stretching slightly between your fingers will "grow" it enough to fit "like a new one". EDIT: A #56 drill is "near as dammitt to a 127 jet
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11-27-2009, 10:52 AM	#2
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Thanks for the info. My daughter's 150 Monster has a top end hiccup that could be described as a surge. I was thinking that the main jet was too fat at 120, but now I think it's too lean. I'm gonna buy more jets and see how it performs, since it has a Uni and a performance exhaust. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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11-27-2009, 07:03 PM	#4
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	10-4. I'll check to see if the manifold is loose or cracked at my next opportunity. I added some ABS as an extension so that the Uni could be placed under the seat; that could pose a bigger problem. Thanks! __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

11-27-2009, 03:03 PM	#3
Reveeen Join Date: Jun 2009 Location: orbital platform Posts: 741	There have been reports of the intake manifold cracking, due to vibration, and the unsupported condition the carb is left in with the stock air box removal. So keep your eyes peeled. The so-called "heavy duty" manifolds http://www.partsforscooters.com/169-...category=74091 ALL seem to be aimed towards the mounting of a 30mm carb.
	0