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just bought a 98 bayou 300 4x4 and having some carb issues. when i go to give gas and accelerate i have to turn my choke on as i ride and when i bring it back down towards a idle i turn the choke off. any body have an idea whats going on with this? also i need new tires and i was wondering if i could fit 25x8x11 on the front and 25x10x11 in the back with out issues. thanks!
 

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Welcome to the Kawie forum.

My guess is your carb needs cleaning.

Not sure on tire question, hopefully some who knows for sure will chime in.
 

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Yes and no. My first concern would be fuel supply. Typically with throttle up and up and up you will have a larger and larger fuel amount requirement. When you choke it, you give it a pseudo increase of fuel by minimizing air in the mix. In your case it sounds like it's starving for fuel as you increase the throttle. This could be jets, throttle adjustment, fuel supply blockage, float adjustment. Since your gonna remove the carb for your rebuild kit, do a couple of checks first:

Shut off fuel at petcock and disconnect fuel line from carb. Be prepared for fuel spillage.

Insert fuel line into container and turn on the petcock.

Monitor fuel flow (on level ground). Just do a common sense "yep, looks like a good flow to me" evaluation.

Remove all lines from carb and remove carb.

Remove bowl.

Invert carb body.

With a line / hose that fits snugly on carb body fuel inlet fitting, blow into the line while holding the floats up a tad from the needle.Slowly let the floats down. This will "seat" the needle. If it seats the needle, you will no longer be able to blow air in. That's what you want. The needle should easily let fuel in and stop fuel as needed. This time, with the needle closed, begin raising the floats very lightly while blowing, In just a second blowing should become easy. This represents the needle allowing fuel in the bowl. Here's a demonstration of the blow technique: https://www.youtube.com/watch?v=Kgog_Ng0-2Q

Float height adjustment is very important

Locate the setting for your application. It will be expressed in millimeters.

I use this method for setting these little pissant carburetors:

Hold the carb at approx a 45 degree angle. What you are looking for is the "tang / tab" of the float assembly just barley touching the small spring-loaded extension of the needle. That small extension will actually depress about a solid millimeter or so. When adjusting the floats, you don't want any depression, but you do want contact with the tab / needle extension.

Float measurement will be performed from the carb body surface that the gasket rests on. Oh yeah, make sure the gasket is removed and you have a new gasket at the ready.
The surface may have a raised ridge. The gasket rests on that ridge. Measure from the ridge, not the slight depression on one side or the other of the ridge. I typically use a 6" stainless metric machinist's rule for my measurements but use what ever you want. I have also used poster board, ice cream sticks, etc marked off with the measurement I need. You measure from the surface to the top (highest point) of the floats (which is actually the bottom of the floats. Sometimes a two float system is all screwed up because of human error . Bending this way and that way leaves the floats uneven from one another. You really want them near perfect as compared to each other.

The float level height adjustment is achieved by bending the tab I referred to. There are several images and videos online to learn from if you need help. After all this do what you want. Regarding rebuild kits, I normally only trust a factory or very top of the line kit when it comes to the quality and preciseness of the assorted jets, valves, etc.

Before you do anything with the carb, clean it very thoroughly and dry thoroughly.

When you make the initial measurement of your floats, it'll be interesting to see if they are adjusted a mm or 2, too high. This will cut of the flow of the amount of fuel you might need for sustained throttle up operations yet be enough fuel for idle. For most applications, it's better to have a tad more fuel than not enough. And a tad more fuel can make your machine run great from idle to WOT but when you shut it all down, you might experience fuel leakage through your over flow line. If your petcock is in good working order, as you are about to kill the engine, shut off the petcock or do it as soon as you shut down the engine.

Back to the float adjustment. Lets say your setting is 17mm. Anything past that, 18, 19, etc will shut the fuel off sooner. Anything lower will allow fuel to come in sooner.

That's about it for the moment.

One more deal. You say you must choke to increase the throttle and I said this appears to be a fuel/air issue. Before you do any of the above, do the following:

Warm the engine until it can idle on its on without the choke. Remove the seat.

With engine running, spry carb cleaner around the attaching point of the large rubber duct to the airbox. What you are looking/listening for is an increase in rpm

Do the same where the duct attaches to the carb, Don't go crazy with the spray but make sure you spray enough. Do the same at the intake where the carb attaches to the engine. Spray the whole friggin' duct. Once again, you're trying to detect extra air being sucked into the carb. If extra air is sucked in other than via the filter / airbox, that can create the need for more gas thus the need for the choke as you have indicated. If you detect leaks, try your darndest to stop them and then see how the machine runs.
 

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thanks for the info bamashooter. I am firefighter398's cousin and have been helping him work on the bike. I am very familiar with carbs, know them very well, have been a mechanic for years. So I'll narrow down a lot of the things you said to check. I know these carbs are notorious for similar issues. When we picked up the bike, it ran like shit, rpm's would not come up at all until the choke was turned on under acceleration. Took the carb apart, thoroughly cleaned and inspected. All the rubber is in good shape, from carb to jug, air box to carb, everything is in great shape and was securely/properly attached. With the carb apart, it appeared in great shape, the previous owner told us they fairly recently did a carb rebuild then started having problems. Put the carb back together, checked it all, diaphragm has good suction. Started it up, fired up immediately, idled great. Went to ride it, discovered that it would only continue to run if the choke was turned on as throttle was increased. My first thought was just as you stated, not getting enough fuel. My next thought was that the previous owner put the wrong jets in it because everything is clean and should work....yet it doesn't. So we got a rebuild kit, arrived today, will be putting it in tomorrow. I really believe its got the wrong jets in it, so I guess we'll see.

With all that said, is there anything specific to these carbs that you can think of to check other than what I've done. Also, the rebuild kit we ordered specified for up to a 2004 I think, yet when it arrived it said 88-95...still ok? or could that be what they put in and its different size jets for the older models?

Also checked the petcock, has great flow through it, and has fresh gas in the tank.

Thanks in advance
 

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Sounds like your cousin is in good hands. Unfortunately, I know nothing about these style carburetors and I'm trying to learn. Regardless of type, a carb is a carb and each style must properly meter fuel and air. I too hope it's improperly jetted. The only thing I can think of at the moment is that since this happens at an increased throttle position, the main jet is what I would be suspicious of. Do you know if his jet needle is the type with the 5 or whatever number of groove ranging from lean (upper) to rich (lower)? Of course it goes without saying that if any jet was modified or swapped, other settings were probably messed with as well. This style carburetor (slide) is very fascinating and appears to be infinitely adjustable and not all that difficult to modify. This is a decent short read though it's for a Mikuni. Mikuni carburetor operation and tuning
 

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Exactly!! a carb is a carb!! I'm trying to keep it simple, usually seems to be the answer. Which is why at this point I'm not looking too much further than simply wrong carb jets, makes sense with the symptoms we've got. And yes, it seems like the main jet is the root of the problem. No it doesn't have an adjustable jet needle The only thing I didn't do was check the float height, which will be getting done with the rebuild. I wish this was a Mikuni slide carb...would make things so much easier...if I had it my way, I'd put Mikuni flat slides on everything! :D

What's your opinion of sonic cleaning?
 

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I've never personally witnessed sonic carb cleaning though a zillion folks swear by it. I would use a mild solution of simple green, the orange stuff, or something like that. I do have a friend who did really high level air brushing and he cleaned his tips, main body, and other guts with sonic cleaning. He had a couple of different size cleaners and both had heating elements. He was obsessed with how well they cleaned his gear. As long as there's no "weak" rubber or plastic parts that the solution could mess up, I think it'd be a good deal.
 

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It looks like...

Looks like, from the OEM Diagram and parts list, that the Main Carb Jet is #125. Also has options of 120, 122, 128, and 130. Be interesting to find out what is in there. Not sure if the rebuild kit comes with one, probably not, but seems like a brand new, CLEAN, #125, should put you on the right TRAIL...
 

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General have to clean or install carb kit on all the carbed quads we get in. Just one of those things have came to count on. Some cases even have to clean the tanks where they have set and collected moisture over the years.
 

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We put the new carb kit in and it runs like a champ. They previous owner had the wrong jets in place so the fuel/air ratio wasn't matching up correctly. Everything's running smooth now!
 

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We put the new carb kit in and it runs like a champ. They previous owner had the wrong jets in place so the fuel/air ratio wasn't matching up correctly. Everything's running smooth now!
Good deal. More than one jet was incorrect and now it's all back to factory? Did you need to readjust air/fuel screw and/or other settings?
 

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They had the main jet and the starter jet switched. I didn't think to check that when I took it apart to clean it the first time. I just took everything apart, cleaned, and reinstalled. I should've checked that though as the previous owner told us that her husband was not mechanically inclined. But as normal, I give people the benefit of the doubt in the sense that I assumed if he didn't exactly know what he was doing, he would've taken one piece out at a time, matched it up, and reinstalled with new....but that obviously wasn't the case. I set everything to factory setting, and everything is working like it should, runs like a champ!
 

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They had the main jet and the starter jet switched. I didn't think to check that when I took it apart to clean it the first time. I just took everything apart, cleaned, and reinstalled. I should've checked that though as the previous owner told us that her husband was not mechanically inclined. But as normal, I give people the benefit of the doubt in the sense that I assumed if he didn't exactly know what he was doing, he would've taken one piece out at a time, matched it up, and reinstalled with new....but that obviously wasn't the case. I set everything to factory setting, and everything is working like it should, runs like a champ!
That's why some people shouldn't open a carb.
The previous owner was one of these people, plus had no troubleshooting skills. If you installed a carb kit on an otherwise good running engine, and the good running engine then ran like crap, where would you start looking for a problem?
 

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Bamashooter- on the one hand, color coding doesn't sound like a bad idea, but it makes it that much easier for those people that have no business being inside a carb to end up inside a carb as novakaw650 said. In this case the two jets are different, same diameter and threads, but the starter jet is about twice as long as the main. I would think that is enough of a "marking" but apparently was not.
 
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