The HOW TO carb adjustment on Chinese quads! - ATV Enthusiast Community

Chinese Quads
Brands such as Jetmoto, Yamoto, Redcat, V-Bike, Hi Bird, and Kazuma

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Old 03-26-2007, 07:30 PM
Extreme Pro Rider
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Join Date: Aug 2002
Posts: 4,263
Default The HOW TO carb adjustment on Chinese quads!

Alot of people have a hard time starting and running the Chinese atv's when new and also when cold. Some of these come with a gelpac in the carb floatbowl for shipping so it does not ruin the float. It is supposed to dissolve when fuel mixes with it. Many make the mistake of driving the atv once started. This is a mistake. You must let it idle for at least 30min for the gel to dissolve. If you do not do this you will risk the chance of clogging the jets and the initial adjustments will not work and it will not run right untill all the gel is gone. Most of the time these will start with the movement of the choke then you can lightly feather the throttle to keep it running. If you can reach the idle screw you can turn it up till you dont have to feather the throttle. After about 30 min you can make the final adjustments. CHANGE THE OIL BEFORE YOU RIDE!!! These come with a cheap shipping oil and must be changed or engine damage will occure. It is best to use an oil that is classified JASO MA certified for 4 stroke or motorcycle engines which are made for wet clutch applications. These have no friction modifiers that are bad for clutches. You can even use diesel oil like Rotella-T 15w40. These oils can be found at your local WalMArt or auto parts store. Synthetics are fine as long as its classified the same as above.

The idle screw is the screw on the carb with a SPRING around it. The air/fuel screw is the flathead screw usually before the idle screw closest to the air filter. Some newer carbs have the a/f screw on the bottom of the float bowl. Here are some basic adjustments to get it started and to tune it once broke in.

The mixture screw had been set-up at the factory before shipment and should not have to be reset. Only a small adjustment may be needed due to climate and elevation. If necessary, refer to the adjustment as below:

1. Make sure the air cleaner is clean.
2. make sure the choke lever is OFF while running.
3. Warm the engine up for 3-5 minutes.
4. Turn the mixture screw clockwise until fully closed,
then turn the mixture screw 2 full turns out.
5. Adjust the idling screw until the engine idles EASILY.
6. Turn the mixture screw slightly clockwise and
counterclockwise until the highest engine REVs is obtained.
7. Adjust the idling screw again until the engine idles
8. Repeat step 6 & 7 till you get the best
The engine idling screw must be set correctly to get a
slowest engine idle(1500 rpm - 1600 rpm), but does not
cut out if you press the accelerator quickly.

Cold weather starting will need an additional adjustment to help aid the starting process.

Most of the manual choke carbs have an adjustable needle inside the carb. Lowering the clip (raising the needle) you will be able to open the throttle and get more fuel into the intake quicker. This helps in the cold weather because the colder the weather the leaner the mixture is. You want richer in the colder weather.

1- Unscrew and pull the top of the carb off with the cable and there will be a slide with the needle in the center. (Notice the way the carb slide came out) In step #6 it must go back in the same way it came out.
2- Disconnect the cable through a small slot in the side of the slide.
3- Now you can take the needle out from the slide.
4- The needle will have a very small e clip in a slot on the needle. The needle will have 5 slots. Lowering the clip is richer the and raising the clip will lean it out.
5- Put the clip on the lowest setting for cold weather. DO NOT DROP THE CLIP! They are very small and hard to find.
6- Reverse the process with installing the needle back into the slide, installing the cable, slide the slide back into the carb and screw the cap tight. Remember in step #1 how the slide came out. It MUST go back in the same way.
7- Now make any adjustments as stated above in the carb tuning.

Remember in step #1 and step #6 I said the slide must go back in the same way it came out? The slide will go in 2 ways. ONLY 1 way is the right way. If the slide is not put in the same way, upon start the quad will take off at full throttle. Make sure when you go to start the quad you have a hand on the kill tether or switch this way if it does take off you can dissable it. If this happens the slide was put back in 180 degrees out. This is very important for the safety of you and anyone standing in front of or around the quad.

These steps will work on 99% of these atv's. They are very hard to get running and people get upset when they turn the key and it does not run. Dont forget these are not set up at a dealer like the name brands so the most basic adjustments are done from the factory. These are built in china and the temps are hot so thats how the adjustments are done. As we all know in America the temps vary and these are not set at all for cold temps.

In some cases you will have tuned the quad and it runs very well but one day it will not idle or has poor performance. Most times it is because the carb has sucked in some debris from the tank. You will have to dissasemble the carb and clean out the pilot and main jet. Make sure you have a good inline fuel filter. This will help prevent this failure.

Hopefully this helps everyone with these concerns. These really do run good once tuned properly and with proper maintenance they will last a long time. And if you have any questions PM me and I will try to help as best as I can. Also once the temps start to get hot you may need to raise the clip for the warmer temps.

Good Luck!

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Old 03-27-2007, 06:56 AM
Join Date: Feb 2007
Posts: 92
Default The HOW TO carb adjustment on Chinese quads!

let me say thank you on behalf of those who won't. i do not have an import, but the way things are looking, i may purchase one soon. so i'm gonna save this page. I don't think i would find a more detailed explaination in any manual.
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Old 03-28-2007, 08:54 AM
Extreme Pro Rider
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Posts: 4,263
Default The HOW TO carb adjustment on Chinese quads!

Thank you very much!
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Old 03-28-2007, 09:55 AM
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Join Date: Jul 2006
Posts: 662
Default The HOW TO carb adjustment on Chinese quads!

Good job 2many, never even thought about it, but it belongs in here as well as the Kid's Quad section.[img]i/expressions/face-icon-small-smile.gif[/img]
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Old 04-17-2007, 11:39 PM
Weekend Warrior
Join Date: Apr 2007
Posts: 5
Default The HOW TO carb adjustment on Chinese quads!

2manytoys... thanks! I'm printing this out to save as well...
A buddy of mine got his entire family Polaris stuff and sold me the stuff his kids learned on...
a 50cc quad, 50cc dirtbike, and 90cc dirtbike... The quad and 90cc dirtbikes ran so-so, the 50cc dirtbike I'm still having some
issues with. With the quad and 90CC, I removed the carbs, disassembled them, cleaned 'em and put them back together, went 1 and 1/2 turns
out on the mixture screw... they fired right up, I set the idle and they've been great ever since.
I looked all over for the intitial setup on the screws and couldn't find it, so I went with what I remembered from my Holley days!! [img]i/expressions/face-icon-small-wink.gif[/img]
I think the 50cc bike is just worn out, but I haven't given up on it yet...
I'd really like to buy everyone the JetMoto quads, but it'll be a long process as I live paycheck to paycheck... anyone know if Raceway finances??
I'm looking for 6 quads... [img]i/expressions/face-icon-small-wink.gif[/img]

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50cc , 90cc , adjust , adjustment , adjustments , atv , carb , carburetor , chinese , float , quad , quads , slide , small , tuning

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