Alot of people have a hard time starting and running the Chinese atv's when new and also when cold. Most 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 made 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 autoparts store. Synthetics are fine as long as it has the same classifications listed 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
EASILY.
8. Repeat step 6 & 7 till you get the best
performance...
*ENGINE IDLES EASILY means:
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.

WARNING!!!WARNING!!WARNING!!!
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!
2many

 

Thanks 2many,

I'm sure that will come in handy....

Jim

 

Your wrote.. Lowering the needle will richen the idle circuit and raising the clip will lean it out. Thats the same thing. I think you miss wrote that. lol

 

lowering the needle will LEAN out the fuel mixture since it drops the tapered part of the needle farther into the main jet nozzle. however, be aware, that this affects part-throttle operation only and should have no effect on idle quality. the more common and effective, albeit complicated, cold weather adjustment is to increase the size of the main jet. 2-cycles seem to be more sensitive than thumpers.

 

2manytoys!!! Thanks for the article you wrote. This was very helpful to me. I just bought a
Kimco MXU 300 this past weekend. I bought it right off the floor so it had zero miles on it. I noticed over the weekend it was hard to start but after 2 min or so it ran fine. Then I read
your article so today I fast idled it 30 min. will see tomorrow how it works out. BTW any
suggestions on what type of oil to use when I change it.Should I go synthetic ? I bought this for my wife . I have an Bomb. Max 400 but after riding this Kimco I think it's awesome.Looks like a well put together machine with alot of detail. Thanks again. Steve

 

Increasing the main will not help much for cold weather starts or even idle.

Carburetor Circuits
Air Screw = Idle to 1/8 Throttle
The Pilot (Slow Jet) = 1/8 to 1/4 Throttle
The slide valve = 1/8 to 1/2 Throttle
Jet needle = 1/4 to 3/4 Throttle
Main Jet = 3/4 to Full Throttle

The pilot jet would be the jet to increase not the main.

2manytoys is correct by making the jet needle richer (by lowering the sir clip on the needle, raising the needle out of the venturi)will increase fuel delivery. The quads / bikes will start easier in cold weather. This is a lot easier than trying to find the correct pilot jet when you don't have the time. I think 2manytoys is trying not to get too technical on jetting principles. They are quick fixes to get the quads started so the kids can get to riding their quads / bikes.

2manytoys:

Good write up. It's too bad you can't make the post a sticky so it always stays on the first page.

 

Thanks smb05

I was going to add the carb circuits but did not want to be too difficult for the average person so I did not include it. In one of the sentences that I wrote I meant to say lower the clip NOT lower the needle. Ok so heres the beginners guide to jetting and if you have any driveability problems this can help find your problem.

Pilot circuit; 0 to 1/4 throttle

Start by bringing the engine up to operating temperature. Open the throttle slightly. Does the engine pick up speed smoothly? If it doesn't, the fuel-mixture screw may be out of adjustment or the pilot jet may be either too small or too large. To determine the pilot screw setting, adjust the idle-speed screw so that the engine is idling slightly fast, somewhere between 10 and 20 percent above the recommended idle speed. Using either the manufacturer's or the jet kit's recommended pilot screw setting as a starting point, turn the fuel screw left or right between 1/4 and 1/2 of a turn. Select the screw position where the engine speed increase is the greatest. Readjust the idle speed to the correct level.

Next, take the bike for a ride, preferably on a relatively quiet, straight section of road. Using your throttle index, run the bike at 1/4 throttle. If the pilot jetting is correct, the engine should run smoothly, and it should be easy to maintain a constant speed without varying the throttle position. If the bike surges or hunts, the pilot jet is probably too small (lean). Other indications that the pilot circuit is lean are popping or spitting through the carburetor when the throttle is opened and popping or backfiring through the exhaust when the throttle is shut. If the pilot circuit is rich, the engine will have a rough idle or may not return to idle without "blipping" the throttle. You may also notice a distinct smell of raw fuel and some eye irritation from the exhaust.

Low- to high-speed transition; 1/4 to 3/8 throttle

Although the throttle cutaway plays a significant role between 1/4 and 3/8 throttle, it is seldom changed when rejetting a streetbike, particularly a cruiser. For that reason I'll gloss over it. Basically the only time the cutaway needs changing is when the transition from the low-speed fuel circuit (pilot jet) to the high-speed circuit (needle, needle jet and main jet) gets seriously out of whack.

Medium throttle opening; 1/4 to 3/4 throttle

The fuel delivery at this stage is controlled by the jet needle and the needle jet. At one time all carburetors came with adjustable jet needles. Once the smog ***** got involved, fixed-position needles became the standard. Jet kits will usually include new needles that can be raised (to richen mixture) or lowered (to make it leaner) to suit or, less often, shims to change the height of your stock needles.

To evaluate the needle/needle-jet performance, run the motorcycle in second or third gear. Roll the throttle on from 1/4 to 1/2 throttle only. The engine should accelerate cleanly without sputtering or bogging. If so, you're all done with the midrange; if it doesn't, you'll need to do some experimenting to determine if the needle position is too rich or too lean. Assuming you've installed adjustable needles from the kit, begin your experiments by trying some alternative needle-clip positions, perhaps a step richer to begin with. If that makes the situation worse, try a step leaner. If the jetting is stock and problems crop up, it's time to order the appropriate jet kit.

Top end; 3/4 to wide-open

Main jets (bottom) may be exchanged for larger or smaller size to make the mixture richer (a greater amount of fuel mixed with the incoming air)) or leaner (less fuel) at full throttle.

At this stage of the game, the majority of the fuel flow is controlled by the main jet (remember some fuel is still flowing through the pilot jet). The time-honored method of determining main-jet size is via a plug chop. If you've never done one, a plug chop is pretty simple. Start with new spark plugs. Run the bike flat out (full throttle), in as high a gear as possible, for eight to 10 seconds (don't hold the bike at the rev limiter, as it'll give you a false reading). Without cutting the throttle or slowing down, simultaneously pull in the clutch and hit the kill switch. Coast the bike to a stop and remove the plug(s). The plug insulator should be tan to grayish-white. A white plug indicates a lean mixture; a dark gray or black one means it's rich. You then select the main-jet size accordingly.

Is It Lean or Rich?

One of the reasons I'm so stoked about jet kits is because they remove 95 percent of the guesswork. Be that as it may, even the best kits require some fine-tuning. Essentially a jetting problem can always be reduced to one of two choices: Is it lean or is it rich?

To determine if the bike is lean (to little fuel for the amount of air reaching the engine through the carburetor) at any given throttle opening, partially cover the air-filter intake with a piece of duct tape; if the carburetion improves, it's running lean. If you suspect the bike is running rich (too much fuel in the air-fuel mixture)), remove the airbox top or the air cleaner element; if the changes are for the better, the bike was running too rich.

If your bike is equipped with a manual fuel shut-off, take the bike for a ride with the fuel turned off. If it runs worse as the float bowl drains, it's lean. If it gets better, it's rich.

Troubleshooting

A lean condition is the end result of too little fuel and too much air. Slightly lean conditions create drivability problems. Worst-case scenario: Lean conditions can and do destroy engines. Holes in the pistons, burnt valves and trashed main bearings are the direct result of lean mixtures.

Rich mixtures are the end result of too much fuel and too little air. Rich mixtures waste fuel, contribute to carbon buildup and pollute the air.

Typical Lean Conditions:

- Poor acceleration; the engine feels flat.

- The engine won't respond when the throttle is snapped open, but it picks up speed as the throttle is closed. (A too-large main jet also mimics this symptom.)

- The engine runs hot, knocks, pings and overheats.

- The engine surges or hunts when cruising at part-throttle.

- Popping or spitting through the carb occurs when the throttle is opened. Or popping and spitting occurs through the pipe on deceleration with a closed throttle.

- The engine runs better in warm weather, worse in cool.

- Performance gets worse when the air filter is removed.

Typical Rich Conditions

- Engine acceleration is flat and uneven and loses that "crisp" feel.

- The engine "eight-strokes" as it loads up and skips combustion cycles.

- The engine's idle is rough or lumpy, and the engine won't return to idle without "blipping" the throttle.

- The throttle needs to be open continuously to maintain acceleration.

- Black, sooty plugs, a sooty exhaust pipe and black smoke from the tailpipe that stinks of unburned fuel.

- Poor fuel economy.

- The engine works better when cold. Performance falls off as it warms up or the ambient temperature rises.

- Engine performance improves when the air cleaner is removed.

 

You are correct, I should have specified. But my experience with these machines is that you can get them to idle reasonably well, it's just when you start to give em throttle that they die (lean).

Sorry if i sounded too critical, didnt mean to. I think we all appreciate when someone like 2many takes the time to help out complete strangers.

 

Hence the reason to raise the needle. I am a mechanic and understand how upset people get when something is not right with the vehicle they have. Most can not do any work themselves anymore because things look so much more complicated then they really are. Thats why I try to help any way I can and I like doing it. If I help 1 person in a day then I feel good. I dont know everything and also learn new things every day. Thats what makes it challenging for me.

When I found out that a member Bruinrider was having problems with her 2 Bajas and saw she lives near me I said I would help. Once I got both tuned and running, the smile on her face was worth a thousand words. Let alone the smile on her kids faces on Christmas morning. It is well worth my time knowing I just made some kids day.

 

You are a asset to this forum 2manytoys. Lots of great advice, stated simply. [img]i/expressions/face-icon-small-smile.gif[/img]

Not sure if I agree with your nickname though, [img]i/expressions/face-icon-small-wink.gif[/img] Just how many is to many? [img]i/expressions/face-icon-small-happy.gif[/img]