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Found 13 results

  1. I have a 1996 King Quad 300 LT-F4WDX ATV I tried to install a carburetor rebuild kit but there were no instructions and I am unable to find them. Anybody know what the "Pilot Screw" is set at? The engine starts but seems to be flooding- very difficult to get the rpms up and engine acts flooded. I set the screw to 3 turns from closed. It is called the "Pilot Screw" on exploded views of the carb. It is a Mikuni BST 31 single carb. Thanks for any help! Bill Roberts
  2. Found this on another site, just wanted to share ,,, its very good !! First off, there's 2 basic fuel related problems. You either have a rich mixture, or a lean mixture. A rich mixture is caused by too much fuel compared to the amount of air being used during combustion. Rich conditions can be detected by the engine spitting and sputtering, blurbling, or acting like a rev limiter, rapidly losing and regaining power. In severely rich conditions, you may be seeing black smoke coming from the exhaust. The black smoke you see is actually raw fuel that is not being burnt and is being wasted. By looking at the spark plug, a rich condition can be detected by a black, sooty plug. A lean mixture is caused by too little fuel compared to the amount of air being used during combustion. Lean conditions can be detected by the engine losing power, yet retaining it's engine speed. For instance, the engine sounds to be accelerating to higher RPMs, yet feels as if it has no power. By looking at the spark plug, a lean condition can be detected by a white, blistered plug. Secondly, there are 3 basic carburetor circuits: Pilot Circuit, Mid-range Circuit, and Main Circuit. These 3 carburetor circuits can be troubleshooted by knowing the throttle opening they control. The Pilot circuit is responsible for throttle openings from Idle (0 throttle) - around 1/4 throttle. This circuit consists of pilot air jet(s), the pilot fuel jet(s), a pilot screw (either fuel or air screw), and pilot ports inside the carburetor throat (a.k.a. Venturi). There are 2 types of pilot screws: a fuel screw and an air screw. The fuel screw is located on the engine side of the throttle slide in the carb, and controls the amount of fuel that is drawn into the Venturi by the pilot ports. By turning the fuel screw out, you are allowing more fuel to pass the screw, effectively richening the mixture. By turning the screw in, you are restricting fuel, effectively leaning the mixture. Another way to determine whether it is an air or fuel screw is that a fuel screw has a rubber o-ring to keep air from entering the pilot circuit around the screw. The air screw is located on the airbox side of the throttle slide in the carb, and controls the amount of air that is drawn into the Venturi by the pilot ports. By turning the air screw out, you are allowing more air to pass the screw, effectively leaning the mixture. By turning the air screw in, you are restricting air, effectively en richening the mixture. The air jets are hardly ever changed, so we won't go over that. The pilot fuel jet(s) can be changed to bigger (richer) or smaller (leaner), depending upon your problem. A good rule of thumb to use is that if you have to adjust the pilot screw more than two turns either way if it's stock setting, then you need to accommodate by changing the pilot air or pilot fuel jets accordingly. Remember, the Pilot Circuit is only effective from 0 throttle to around 1/4 throttle. It still functions during the rest of the throttle positions, but it's effect is minimal, and goes un-noticed. The Mid-range circuit is responsible for throttle openings from 1/4 throttle - 3/4 throttle. This circuit is controlled by 2 things: the Jet Needle, and Needle Jet (a.k.a. the Main Jet Holder). The Jet Needle, or needle as many call it, is attached to the throttle slide, and drops into the Needle Jet. All needles are tapered. Either the Jet Needle is adjustable or it is not. If there are more than 1 grooves for the needle clip to sit in, then it is adjustable. By raising the clip on the needle, you are allowing the needle to sit deeper into the needle jet, which restricts fuel, effectively leaning the mixture. By lowering the clip on the needle, you are raising the needle out of the needle jet, which allows more fuel to pass, effectively en richening the mixture. When the slide raises, it raises the needle out of the needle jet, allowing fuel to pass by the needle and into the Venturi. This is where needle taper comes into play. Unless you are extremely fine tuning the carb, you don't need to worry about taper. You change which part of the taper is in the needle jet by the position of the clip. Remember, the Mid-range circuit is only effective from 1/4 throttle - 3/4 throttle. None of the other circuits have a drastic effect on this circuit, so if your problem is in the mid-range circuit, then it can't be the main jet or the pilot jet. The Main circuit is responsible for throttle openings from 3/4 throttle - Wide Open Throttle (you'll see me refer to this at WOT later on). This circuit is controlled by 2 things: the Main Jet, and the main air jet. The Main Jet is the #1 thing that people change in a carburetor when it comes to tuning them. This is often a big mistake, as it only controls 3/4 - WOT, and NOTHING ELSE. Remember that. A larger main jet will allow more fuel to pass through it, effectively en richening the mixture. A smaller main jet will restrict fuel, effective leaning the mixture. With the main air jet, it allows air to premix with fuel as it goes up into the Venturi. The Main Jet only functions at 100% when the slide is open and the jet needle is pulled completely out of the needle jet. At this time, the only thing restricting fuel flow into the Venturi is the size of the Main Jet. Now for tuning. If you read above, you should know the difference in feel of rich and lean mixtures. By knowing at what throttle opening the problem is occurring at, you can figure out what circuit the problem is occurring at. If it's the pilot circuit, there are 3 basic way to tune the circuit. You can adjust the pilot screw, change the pilot air jet, or change the pilot jet. Adjusting the pilot screw is simple. With the engine running at idle, warmed up to normal operating temps, turn the screw in until it starts to idle rough, then turn the screw out until it starts to idle rough, then turn the screw so it's between those two extremes. To check the position of the screw, you can count the number of turns as you turn the screw in until it seats SOFTLY with the carb body. Reason I capitalized SOFTLY is that the screws (especially the fuel screws) are easily damaged if over tightened. So screw them in until they SOFTLY seat the carb body. Compare your counted number of turns to soft seat and compare it to stock settings (stock settings are determined by counting turns until soft seat before you do any adjustments whatsoever). Again, if you had to turn the screw more than 2 turns either way, you need to change pilot jets (air or fuel) accordingly. In the mid-range circuit, there are 2 basic ways to tune the circuit. You can adjust the jet needle, or change the needle jet. Raising the clip will lower the needle, leaning the mid-range. Lowering the clip will raise the needle, en richening the mid-range. You can also change the needle jet, but only if your jet needle adjustments make no difference in the way the mid-range circuit operated. If you are running lean on the mid-range, and you've raised the needle as far as it will go and it doesn't get any better, then you should go up in the needle jet size. Many carb manufactures don't have different sized needle jets, so the aftermarket may offer them, or they may not. In the main circuit, there are 2 basic ways to tune the circuit. You can change the main jet, or change the main air jet. Changing to a larger main jet will effectively en richen the circuit. Changing to a smaller main jet will effectively lean the circuit. You can determine which you need to do by first determining whether you are rich or lean. Changing main air jets, again, is for very fine tuning. Once you have the main circuit functioning properly, you shouldn't have to worry about the main air jet, because the air for the circuit is mostly provided by the air passing through the Venturi. On many carbs, the main air jet is not changeable. They may be pressed in. So there you have it. I basically touched base with carburetor internals and how to adjust them to tune the carb. Every brand carburetor has different ways of accomplishing the same main goal of every carburetor. That goal is to precisely and efficiently mix air and fuel in the right ratios for efficient engine operation. This efficient operation comes from complete combustion, which cannot occur if you are too rich. Whether Mikuni, Keihin, or whatever, they all do the same thing, just in different ways. Hopefully this will help some of you to understand the functions of the carburetors internals. Lastly, you all need to know... ***This is only a reference guide. This is not to be used as a manual for any specific carburetor, as every carb is different. This is only a guide to be used to base your carb tuning off of. In no way am I responsible for the adjustments, or their results, you make on your own machine.***
  3. I was just given a 1996 wolverine for Christmas from my father in law, needs a new carb. The cheapest that I can find a new one is $500, looks like it's an oddball carb. Is it possible to use a warrior carb which is a lot less expensive and more available? I found an aftermarket wolverine carb for like $170, anyone had any luck with these? Thanks!
  4. Hello to all, I am new to your site. Need to pick your brains, I recently bought and older quad for some work around the house. It runs alright but it looks like over the years some things have been cobbled up. My main thing is the carburetor, Its not the original mikuni it has some japan thing that has been modified to fit and it has been a pain. I want to put a mikuni back on it, the clymer manual shows the original as a vm22sh mikuni carb. Kinda hard finding one, I was thinking of going that way, then rebuild it. Or can I get another vm22 model and put on it, or will that be more of a problem? I have been seeing them on ebay for about $75 I have noticed the jetting is really different then what they are calling for in the manual. Any help would be appreciated thank you. Once again this is for a 86 yfm 200.
  5. What are the starting point settings for the carb for this machine? Thanks Bruce
  6. When I get to mid throttle (slide is 1/2 way up) the engine sputters. All other ranges are fine. It all started back when my gas cap was not tight and all the gas evaporated. Sputter problem has remained since then. If I fully clean the carb, install it, it runs good, but the next day, the sputter returns. When it is cold, no sputter, but returns as engine warms. When the peocock valve is turned off, the sputter stops, then it runs out of gas (that tells me the sputter is caused by running to rich, right?). Things I've done but problem returns. -disassembled carb (about 10 times) and cleaned all jets, passages, rechecked float level -ran without air filter -changed to smaller jets (main and pilot) -moved needle valve to next leaner position -set float level too hight and too low -cleaned peacock and inline filter -ran with gas cap loose -checked spark plug--black with a little bit of white My only idea now is that the plastic around the needle jet has deteriorated causing it to run rich. I don't have a smaller needle jet, but adjusting the needle position didn't do anything. Ideas? Thoughts? Thanks. Jim
  7. What makes the value piston work up and down. Its will run idle but when you give it the gas the piston in the carb will not move up. First time to ever work on carb on this type atv. Need help Please. This is a 2005 Suzuki Quad Vinson 4x4. Thanks Mowerman
  8. My dad said if I wanted a four wheeler I had to build it. Well it took me over a year to do it but now I am having troubles with the carubretor. My dad and I tried to rebuild it and we took our time doing it but the problems we are have are: we are getting exhaust blow out of the carburetor and exhaust out of the tailpipe it back fires at a high rpm and when we put the air box on the carburetor we have no acceleration. We have stop at a couple dealerships but they don't work on anything as old as my 88 warrior and have no idea. Can anyone help please. You can email me at [email protected] Tags: Rebuilt Engine Carburetor
  9. My dad said if I wanted a four wheeler I had to build it. Well it took me over a year to do it but now I am having troubles with the carubretor. My dad and I tried to rebuild it and we took our time doing it but the problems we are have are: we are getting exhaust blow out of the carburetor and exhaust out of the tailpipe it back fires at a high rpm and when we put the air box on the carburetor we have no acceleration. We have stop at a couple dealerships but they don't work on anything as old as my 88 warrior and have no idea. Can anyone help please. You can email me at [email protected] Tags: Rebuilt Engine Carburetor
  10. Can anyone direct me to a place where I can buy a carb rebuild kit for my 2005, arctic cat, 400, 4X4 ? I have been searching the internet and I can't find the kits for any arctic cats... Thanks for any assistance.
  11. I have just recently purchased a 1998 artic cat bearcat 454 2x4! It had been sitting up for about 2 years and needed some major work! I replaced the cdi unit and regulator and freed up the brakes! Now I was breaking down the carb, cleaning the jets and all and noticed that one of the ears that hold the float in place has been broken off!! I opoxyed it back on, and everthing seems to be fine now! But as I was looking for carbs I can't find an aftermarket carb anywhere! A brand new one is from 400 to 500 bucks and I can't find a used one! Does anyone know a different brand or an aftermarket carb I can use on my 98 bearcat 454?? Thanx alot!!
  12. Carburetor Theory Whether carbureted or injected, the fuel system is designed to provide the optimum mixture of air and fuel to the engine under varying conditions. This optimum air/fuel ratio (do not call it the fuel/air ratio!) is called the stoichiometric ratio and in theory is approximately 14.7 parts of air to 1 part gasoline (14.7:1) based on weight, not volume. However, this air/fuel ratio must be modified under different atmospheric and running conditions. A ratio numerically higher than 14.7 would be considered a lean air/fuel mixture, numerically less than 14.7 would be considered a rich mixture. There are several principles of physics that affect the design of carburetors. Among these are; a liquid will take the shape of the container it is in liquids are not compressible liquid in two containers joined with a passageway will be at the same level if the atmospheric pressure above them is the same air will flow from a high pressure area to a low pressure area to try and equalize the imbalance air flowing through a restriction in a passageway (the venturi of a carburetor) will increase in speed and decreases in pressure at the point of restriction a liquid can be atomized and vaporized There are three basic types of carburetors, fixed venturi, mechanical slide and constant velocity (CV). Despite their differences, they all use the Venturi Principle which states that air flowing through a restriction will increase in speed and decrease in pressure. It is the decrease in pressure in the carburetor venturi that allows atmospheric pressure to push fuel into the venturi through passageways that are machined into the carburetor body. These passageways contain jets that control the amount of flow through them. In order to burn properly and efficiently, the fuel must be first atomized (broken down into a fine mist) and then vaporized, that is, changed from a liquid to a vapor. When the air/fuel mist enters the combustion chamber, engine heat helps vaporize the fuel. However, when the engine is cold the fuel does not vaporize as completely, so we must supply more fuel so that enough of it is vaporized for the engine to run. This is the purpose of the cold start mechanism (commonly called the choke) used on carbureted engines. Carburetor Cold Start Mechanisms There are currently two type of cold start mechanisms used in carburetors, the choke plate and the enrichener. The choke plate pivots to block off some of the incoming air, while the enrichener adds more fuel. Both methods result in the same condition, that is, a rich mixture in the neighborhood of 3:1. A fuel injection system does this by automatically increasing injector duration, which is how long the injector sprays fuel into the combustion chamber. The longer the injector duration, the more fuel is sprayed into the engine and the richer the mixture. Running a carbureted engine that is at or close to operating temperature with the cold start mechanism on will result in a rich mixture when it isn't needed and can result in fouled spark plugs. Carburetor Circuits Carburetors are mechanical/hydraulic/pneumatic devices that have several functions. They allow us to change engine speed by allowing more or less air/fuel mixture to enter the engine, they help atomize the fuel for better vaporization, and they provide varying air/fuel ratios under different throttle positions. For an engine at operating temperature, there are three basic fuel circuits. Pilot Circuit Also known as the idle circuit or the slow speed circuit, it controls the air/fuel mixture while the engine is idling and up to about 1/8 throttle opening (it also flows fuel at larger throttle openings but the effect is negligible). Because of the small amount of fuel that is required at idle speeds, the pilot fuel passageway is restricted by the pilot jet. Carburetor jets (of any type) are usually made out of brass and come in different sizes. A number is stamped on the jet during manufacturing, the larger the number the larger the opening in the pilot jet and the richer the mixture would be. Because of the very small size of the opening in a pilot jet, is can easily be blocked by dirt, rust, stale fuel deposits or other debris. When this happens, the engine will not idle properly and the carburetor(s) will have to be removed, disassembled and cleaned. Mid-range Circuit As we open the throttle to accelerate, the carburetor allows more air to enter the engine, and there must be a corresponding increase in the amount of fuel flow. In most cases, this is accomplished by the use of a slide and jet needle, whether it is a mechanically operated slide or a vacuum operated slide. The jet needle raises and lowers with the slide and fits into a brass tube called the needle jet. Do not get confused between the two, the jet needle moves up and down while the needle jet is stationary in the body of the carburetor. The jet needle is tapered so that as it is raised in the needle jet, there is more space between the two and more fuel is allowed to flow. This circuit regulates the air/fuel mixture primarily from 1/8 throttle to about 3/4 throttle. Main Circuit As the throttle is opened approaching full throttle, the carburetor allows even more air to enter the engine and the main jet now controls the amount of fuel that is supplied. As with the pilot jet, it is usually made of brass, comes in different sizes and has a number stamped on it. Again, the larger the number, the larger the opening and the more fuel is supplied for a richer mixture. Larger main jets are often required with changes to the intake and exhaust of the engine. The opening in a main jet is much larger than a pilot jet and is less likely to be blocked or restricted. This circuit regulates the air/fuel mixture primarily from 3/4 throttle to wide open throttle.

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