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Post by david3336 on Aug 18, 2013 16:14:41 GMT -5
does the idle jet give fuel at top end speeds. i found on my 150cc that at around 65mph it sputters a lil then will go on and smooth out and go on up to 70+ mph with a/f screw set at anywhere between 2 1/2 to 3 1/2 turns out but if i go to like 4 or 4 1/2 turn out it smooth all way to top speed of around 75mph i have free flow air filter and muffler on it. so i am think i need to go to a 38 or 40 idle jet right now its a 35 idle and 115 main with 112 main it sputtered at around 60 no matter what i did with a/f screw any ideas would be great i know im already running faster than most 150cc but would love to get this glitch out so it smooth all way through.
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Post by devo344a on Aug 18, 2013 18:59:33 GMT -5
I believe the Idle jet quits at around 25mph
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Post by Deleted on Aug 18, 2013 19:02:50 GMT -5
first quarter throttle regardless of speed i believe.
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Post by david3336 on Aug 18, 2013 19:17:44 GMT -5
if thats the case why does adjusting a/f screw make a diffarents in how my top end acts. i thought it cut out too at a set point its a new carb i put on when i rebuilt motor like 600 miles ago problem been here the whole time i have play with main jet and a/f setting and got it to as lil as i can. so thats why im thinking bigger idle jet cause i have to give it a lil gas to start it up too
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Post by alleyoop on Aug 18, 2013 19:38:18 GMT -5
David3336 your correct, Contrary what just about everyone believes the Pilot Jet feeds fuel all through the throttle range. As it transitions onto the Main jet it feeds less fuel but still adds fuel to the mixture along with the main jet. Alleyoop  |
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Post by david3336 on Aug 18, 2013 19:54:55 GMT -5
alley you always show up when things get tough on me here at my shop and i wanna say thanks for all your help. so i know u read my post do you think moving the needle clip will help this problem or just try 38 and 40 idle jet or am i just off base all togeather set up rt now is 112 main and 36 idle at around 65 it shutters and you can hear it from muffler as well as feel it in the bike and see it in tiny tach but if you hold wot it will pass and smooth out if u on flat ground or down hill run and go on to run rt at 75mph when it starts the rpms are rt at 8000 if that makes any diffarence and at top speed 8800 rpms at 75 mph i thought the 115 mj helped but it didnt it just moved it to a diffarent speed and kinda killed my top end a lil so the 112 mj and about 4 turns out on af screw is where it best and at where the problem is as described above
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Post by alleyoop on Aug 18, 2013 20:05:55 GMT -5
Moving the needle up will only help in the MID RANGE but nothing on the top end.
In your case you have a little stumble on the top end and runs good all the way till that point so I would leave the needle and Pilot jet that you have. Since the problem is only at the very top end I would get the next bigger Main Jet You always want to run a tade on the rich side on the top end anyway. The reason for that is that is where major damage can be caused by a lean run which can happen with any air leaks and or tight valves.
Alleyoop
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Post by david3336 on Aug 18, 2013 20:13:41 GMT -5
i tried a 115 and could not get it to act rt either
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Post by david3336 on Aug 18, 2013 20:17:48 GMT -5
with the 112 i can close down the a/f screw to a point i think it stops but then it will only reach like 65 mph tops i loose alot of top end speed. it dont even make sence to me why it does that its seems to need more fuel to reach its full speed but then when i give it more fuel it shutters. and cant find a setting between that works well
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Post by alleyoop on Aug 18, 2013 20:25:44 GMT -5
Well like i said according to your describing the problem and what you did to get rid of the stumble it is running on the edge and just needs a little more fuel. Looks like a 115 is to much fuel and a 112 is almost there so try a #38 Pilot Jet unless you can find a 113 or maybe even a 112.5 Main. On mine I am running with a 122.5 main jet a 125 was to much it would POP at the top end. It runs with a 120 but that is on the LEAN EDGE.
Alleyoop
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Post by david3336 on Aug 18, 2013 20:30:35 GMT -5
ok i try that. i got another post on here that has not got any reply will u take a look and let me know what u think it is the one kymco 50cc wont idle
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Post by david3336 on Aug 19, 2013 20:28:32 GMT -5
got a 112.5 mj and a 38 ij coming end of the week i hope, we see what happens. ill post my findings. thanks for help
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..BAD TO THE BONE..