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Post by rcq92130 on Feb 16, 2015 20:29:17 GMT -5
Yes, but it PRIMARILY is to adjust mixture at idle and low rpm.
To get good open throttle performance you THEN need to attend to the main jet
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Post by JoeyBee on Feb 16, 2015 20:35:56 GMT -5
I surprised you are even taking it out. The news keeps claiming you guys are getting a "biblical" amount of snow. My scoot would be sitting in the garage waiting for warmer weather. But it looks so sexy at night in the snow!  I see so the mix screw only changes the pilot, but would't that still affect the mix of the main jet as well since the pilot jet doesn't shut off when the main jet is in use does it? I found this chart very helpful when tuning my carb.  |
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Post by alleyoop on Feb 16, 2015 20:37:19 GMT -5
Bogging on take off has nothing to do with the main jet PERIOD. Main jet comes in around 40mph.
So if it is bogging on takeoff when you twist the throttle it is GETTING TO MUCH AIR not enough fuel. So you have TWO options cut some of the air off or feed it more fuel.
The Pilot Jet feeds fuel all through the throttle range of course little less as the needle is coming out around 40 or so mph or on the 50s 20 or so mph.
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Post by lain on Feb 16, 2015 20:52:45 GMT -5
But it looks so sexy at night in the snow! I see so the mix screw only changes the pilot, but would't that still affect the mix of the main jet as well since the pilot jet doesn't shut off when the main jet is in use does it? I found this chart very helpful when tuning my carb. Saved that image, should be helpful thanks! |
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Post by JoeyBee on Feb 16, 2015 21:16:24 GMT -5
lain. No problem. alleyoop had posted on several forums. I printed it out and posted next to my workbench.
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Post by JerryScript on Feb 16, 2015 21:31:57 GMT -5
alleyoop, I'm a bit confused, I didn't think the time when the needle/throttle rises had anything to do with speed, but only RPMs? If so, and your RPMs are rise significantly at takeoff, then the needle is rising before you reach speed?
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Post by lain on Feb 16, 2015 21:37:07 GMT -5
lain. No problem. alleyoop had posted on several forums. I printed it out and posted next to my workbench. What is throttle valve cutaway? |
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Post by alleyoop on Feb 16, 2015 21:41:01 GMT -5
lain. No problem. alleyoop had posted on several forums. I printed it out and posted next to my workbench. What is throttle valve cutaway? That is WIDE OPEN BUTTERFLY the butterfly is horizontal and allowing all the air in. |
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Post by rcq92130 on Feb 17, 2015 13:19:22 GMT -5
Bear in mind, Lain, that it is incorrect to believe your carb will switch between pilot and main jets based upon how fast your scooter is going. Your scooter engine has no idea what the road velocity is and knows only the load you are demanding from it.
the load on an engine is related ONLY to rpm and throttle (vacuum of the engine). If your engine is operating at WOT and 7,000 rpm it does not matter if the scooter is traveling at 10mph or 50mph - the engine load will be the same. At low speed the engine's output will be used to accelerate; at high speed to overcome air resistance. But the engine output will be the same --- and the carb. responds according to load, not road speed.
So, to understand what in the carb is not quite right, try to pay attention to where in the power curve it is bogging. If it's at moderate throttle, low engine speeds (lower rpm), low acceleration you have a pilot adjustment to do. If it's at WOT (regardless of road speed) and high rpms you have a main jet to adjust.
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Post by lain on Feb 19, 2015 15:03:39 GMT -5
So after riding it a few more times and listening to it and paying attention, I find that the bogging happens (in reference to the carb tuning graph picture) from right off idle to about 3/16 throttle to where the jet needle kicks in, then it speeds up rapidly to about 1/3 power and does not bog over that point. So should I raise the needle? I tuned the fuel/air mix but cannot get any better than what I have it at now. It is set slightly rich right now. Tuning it lean does not get rid of the bogging.
The high end seems to be "wanting." Like I feel at about 3/4 throttle that no more throttle above this will make it go any faster. It also makes a higher noise than normal if I try to go full WOT, but does not go faster than 3/4 throttle. Would this be something to tune by changing the main jet or air intake, not sure which?
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Post by JoeyBee on Feb 19, 2015 16:11:30 GMT -5
So after riding it a few more times and listening to it and paying attention, I find that the bogging happens (in reference to the carb tuning graph picture) from right off idle to about 3/16 throttle to where the jet needle kicks in, then it speeds up rapidly to about 1/3 power and does not bog over that point. So should I raise the needle? I tuned the fuel/air mix but cannot get any better than what I have it at now. It is set slightly rich right now. Tuning it lean does not get rid of the bogging. The high end seems to be "wanting." Like I feel at about 3/4 throttle that no more throttle above this will make it go any faster. It also makes a higher noise than normal if I try to go full WOT, but does not go faster than 3/4 throttle. Would this be something to tune by changing the main jet or air intake, not sure which? Okay, from how you describe it, sounds like right you are running rich then lean. Try raising your needle and upping your main jet one size. |
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Post by lain on Feb 21, 2015 11:48:12 GMT -5
So after riding it a few more times and listening to it and paying attention, I find that the bogging happens (in reference to the carb tuning graph picture) from right off idle to about 3/16 throttle to where the jet needle kicks in, then it speeds up rapidly to about 1/3 power and does not bog over that point. So should I raise the needle? I tuned the fuel/air mix but cannot get any better than what I have it at now. It is set slightly rich right now. Tuning it lean does not get rid of the bogging. The high end seems to be "wanting." Like I feel at about 3/4 throttle that no more throttle above this will make it go any faster. It also makes a higher noise than normal if I try to go full WOT, but does not go faster than 3/4 throttle. Would this be something to tune by changing the main jet or air intake, not sure which? Okay, from how you describe it, sounds like right you are running rich then lean. Try raising your needle and upping your main jet one size. Can I just adjust the fuel/air mix screw and up main jet? What does raising the needle do? I can adjust the pilot to be leaner if I needed, but the way I have it set now it starts really easily and stays idling in negative temperatures. |
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Post by jerseyboy on Feb 21, 2015 13:00:11 GMT -5
Did you try raising the needle a little bit,,I never played with mine,,not even sure if it has a clip with different slots,,or you have to shim it with small washers?
I know when playing with motorized bike motors the needle being moved up/down plays a big role in how they run through the band....not too sure on GY6's.
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Post by JoeyBee on Feb 21, 2015 13:04:43 GMT -5
lain. Raising the needle leans the carb before the main jet kicks in. Try raising it one notch to see if the bogging at take off reduces. After raising it you may have to richen the fuel mixture screw a dat to balance the idel. But just a little.
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Post by lain on Feb 21, 2015 13:37:52 GMT -5
lain. Raising the needle leans the carb before the main jet kicks in. Try raising it one notch to see if the bogging at take off reduces. After raising it you may have to richen the fuel mixture screw a dat to balance the idel. But just a little. wouldn't raising it open up the jet a bit and allow fuel in earlier making it rich? |
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..BAD TO THE BONE..
