Carb Tuning Help

whitney1207 · 05-05-2014, 08:30 PM

I downloaded a manual online for my 50cc scooter. I've been having problems with it so i cleaned the carb out but i need help tuning it.

According to the manual: http://www.chinesescooterreference.c...otermanual.pdf

1. Adjust idle 1800 rpm for the 50cc with idle screw.
2. Turn air/fuel mix (fuel volume regulation) screw all the way in gently.
The engine should stop.
3. Turn the air/fuel mix screw out 1 ½ turns on the 50cc.
4. Start engine and increase idle (with idle screw) to a fast idle.
5. Slowly turn the air/fuel mix screw out until maximum idle speed is
achieved.
6. Readjust idle screw to proper idle speed.
7. Check for stability by accelerating a few times. If engine doesn t
accelerate smoothly, readjust.

1. i have to adjust the idle to more like 14-1500 to get it to cut out with the air fuel screw all the way in.

2. They say adjust to a "fast idle" and I dont know what that is. (I tried 2000 RPM's)

3. When i keep backing the air/fuel screw out it does not increase the idle at all.

blueboy5000 · 05-07-2014, 06:44 AM

That's wrong. Seat the mixture screw and turn it out 2 and 1/2 turns, do not worry about idle, if the bike stalls with the mixture screw set to that, turn up the idle screw till it stays running.

Then turn the mixture screw out another 1/4 turn and see if the RPMs increase. If they do, repeat until the RPMS no longer increase. Once you have found the MAXIMUM RPM, turn the mixture screw IN 1/2 turns and LEAVE IT. This should be a slightly rich mixture, which should be ideal.

Then set your idle between 1600 and 1800 RPMS.

dwint51 · 05-07-2014, 08:48 AM

make sure the engine is totally warmed up

4getful2 · 05-07-2014, 06:03 PM

An idle of 1600-1800 sounds a bit high. you may just want to put the machine on it's center stand, if it's not already, and check that the rear tire is not spinning and it shouldn't be.

whitney1207 · 05-07-2014, 09:16 PM

the clutch doesnt engage till 4500 or so.. i usually do the adjustments on the center stand just in case it does engage it doesn't go flying

Thanks for the advice I will try it

twowheeler · 05-07-2014, 10:36 PM

If adjusting has no effect your jet is plugged up.

whitney1207 · 05-08-2014, 09:51 PM

ok, thanks.. I have a weird main jet so i'm trying to figure out how to replace it.

05-07-2014, 06:44 AM	#2
blueboy5000 Join Date: Jul 2011 Location: Connecticut Posts: 493	That's wrong. Seat the mixture screw and turn it out 2 and 1/2 turns, do not worry about idle, if the bike stalls with the mixture screw set to that, turn up the idle screw till it stays running. Then turn the mixture screw out another 1/4 turn and see if the RPMs increase. If they do, repeat until the RPMS no longer increase. Once you have found the MAXIMUM RPM, turn the mixture screw IN 1/2 turns and LEAVE IT. This should be a slightly rich mixture, which should be ideal. Then set your idle between 1600 and 1800 RPMS. __________________ 2011 Roketa MC-23-150 4T 150cc 157 qmj 24mm carb w 115 main jet and paper cone air filter Manual petcock w Tygon fuel lines Scrappy Dog Scooters Retro-slash stainless straight-thru exhaust RED spring clutch Adjustable CDI (brand unknown, it's blue and red and works great!) KOSO high performance variator w 12g sliders Gates Powerlink 835-20-30 belt GPS verified 65mph on flats.
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05-07-2014, 10:36 PM	#6
twowheeler Join Date: Feb 2014 Posts: 46	If adjusting has no effect your jet is plugged up. __________________
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05-08-2014, 09:51 PM	#7
whitney1207 Join Date: Apr 2014 Location: Las Vegas, NV Posts: 32	ok, thanks.. I have a weird main jet so i'm trying to figure out how to replace it. __________________ D_Whitney 50cc Taotao VIP 139qmb, 18mm carb
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05-07-2014, 06:03 PM	#4
4getful2 Join Date: Mar 2013 Location: illinois Posts: 65	An idle of 1600-1800 sounds a bit high. you may just want to put the machine on it's center stand, if it's not already, and check that the rear tire is not spinning and it shouldn't be.
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