90cc airbox removal/Jetting???????
#21
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Bendman, I may have mistakenly assumed the dealer checked for proper fuel flow to the carb when you took it in the last time. You said they found trash in the system. Just as a check, take the fuel line off the carb and turn the fuel on. It should have a steady flow of fuel. That line is much much bigger than the hole in the needle seat, so it should flow enough if no blockage in the tank, petcock, or fuel line.
You have drilled out to .080" on the needle seat, which should be more than enough. To check it on a stand, you'll have to hold the throttle wide open for awhile to give it time to run the float bowl dry. You can check it this way if the rev limiter is still in place. I know its frustrating, but a lean mixture can cause similar misbehavior. The stock jet may have to go up one size if the weather is real cold and dry where you are or if the air box system has been modified any at all.
Mars, just to be clear, we are drilling the float needle seat, not the main jet. But if we were drilling the main jet, I'm not sure I understand the problem your talking about on the main jet taper - I may have misread your post, though. The needle slides down inside the main jet at idle, but fuel flow is metered at the top of the needle where it meets the carb bore, not at the main jet; once you begin to open the throttle, it leaves the main jet completely and fuel is regulated by the varying taper of the needle at the carb bore.
222
You have drilled out to .080" on the needle seat, which should be more than enough. To check it on a stand, you'll have to hold the throttle wide open for awhile to give it time to run the float bowl dry. You can check it this way if the rev limiter is still in place. I know its frustrating, but a lean mixture can cause similar misbehavior. The stock jet may have to go up one size if the weather is real cold and dry where you are or if the air box system has been modified any at all.
Mars, just to be clear, we are drilling the float needle seat, not the main jet. But if we were drilling the main jet, I'm not sure I understand the problem your talking about on the main jet taper - I may have misread your post, though. The needle slides down inside the main jet at idle, but fuel flow is metered at the top of the needle where it meets the carb bore, not at the main jet; once you begin to open the throttle, it leaves the main jet completely and fuel is regulated by the varying taper of the needle at the carb bore.
222
#22
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222 Thanks for your help. I checked the fuel line to make sure it was getting fuel. It has a steady stream of gas coming out it’s not much but its steady. I checked the plug and for my taste it’s a little light. I don’t know though. The color is kind of like a light gray with a purple hue. Too lean maybe like you were saying?? Thanks to you I know where the main jet is know I could change it.
#24
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Originally posted by: 222
BIG SNIP>
Mars, just to be clear, we are drilling the float needle seat, not the main jet. But if we were drilling the main jet, I'm not sure I understand the problem your talking about on the main jet taper - I may have misread your post, though. The needle slides down inside the main jet at idle, but fuel flow is metered at the top of the needle where it meets the carb bore, not at the main jet; once you begin to open the throttle, it leaves the main jet completely and fuel is regulated by the varying taper of the needle at the carb bore.
222
BIG SNIP>
Mars, just to be clear, we are drilling the float needle seat, not the main jet. But if we were drilling the main jet, I'm not sure I understand the problem your talking about on the main jet taper - I may have misread your post, though. The needle slides down inside the main jet at idle, but fuel flow is metered at the top of the needle where it meets the carb bore, not at the main jet; once you begin to open the throttle, it leaves the main jet completely and fuel is regulated by the varying taper of the needle at the carb bore.
222
I'll go back to my corner now.....
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