I picked up a 98 Mojave that has a k&n filter, a jet kit, and a cobra exhaust. When I bought the thing, he told me i had to run it with the choke half on. I rode for a couple of days and had some carb problems, so I checked it out. Its a pain cas you have to take off all the plastics. Much easier to work on a bike, this is my first quad. I have had a cbr600, a yzf 600r, an rt100, and a ttr230, so two streetbikes and two dirtbikes, but my first quad. The first couple of days this thing had *****, It surprised me for a 250, it was fast, and i could wheelie it without using the clutch.

Anyways, i took it apart and found that the boot that connects the airbox to the carb has a spring to create tension rather than a clamp to hold it onto the carb. That spring was worn and allowed the boot to slip off, so all the time i was sucking air in straight into the carb, bypassing the airbox. That is how all the dirt got in and clogged up the jets and made my quad choke up on me. The bowl was filled with crap. Anyhow, my buddy cleaned out the carb and replaced the needle and reset the clip, put the carb on with a clip tis time (no spring) tuned it, and it started right up no problem. Its has been running very smooth, not puking and poping, nice idle, and smooth throttle without choking up or backfiring.

The thing is, now it is ALOT slower. It has to be because it is taking air through the airbox now, I know these things are restrictive but i didnt think they could make this much of a difference. I can not pop the front end up now without using the clutch. On the road, i can get in to fith and cruise, and it is wiered there is not the power there was before, and it is slower top speed. The motor you can hear is not going to go any faster when the throttle is about 25 to 50% open. If i am cruising at the top speed, my thumb is only pushing the throttle less than half way, and if i give it more throttle there is no response, it does not speed up. So, it must need more air right?

How do I get more air? Can i just drill like a one inch hole in the upper part of the airbox? Or where? Or what else can I do? Maybe theres another problem because it is just way slower. Maybe it wasnt supposed to be that fast? I dont know I am used to speed riding street bikes, maybe a mojave is supposed to be this slow? What can I do?

 

Here are the basics of carburation: Pilot Jet = 0 to 1/4 throttle. Needle = 1/4 to 3/4 throttle. Main Jet = 3/4 to Full Throttle. So either your filter is extremely plugged, your air boxes have something restricting the flow, or you have a problem with your needle not raising up all the way and letting your main jet kick in. If your diaphragm at the top of the carb doent have a good seal or leaks air, it will prevent your slide & needle from raising - this is where I would start. If you are convinced that it is just a lack of air through your airbox, get a direct fit clamp on air filter and see what it does (the main disadvantage of this kind of filter is that you cannot go thorough deep mud/water, but you get a LOT more air than if you route it through the airbox). You could take off the tube on the back side of the carb, use a mirror, and with your atv running give it throttle and see if the slide goes all the way up (you dont have to wait for the atv to reach max rpms - the slide should go up before the rpms catch up). if it doesnt then either use something that wont marr the carb or just use your finger and manually raise the slide to see if the atv sounds more like it should. I would make sure that your atv is clean so that you dont accidentally suck in dirt before you do this though. Also, I was going to ask- you said "Anyhow, my buddy cleaned out the carb and replaced the needle and reset the clip, put the carb on with a clip tis time (no spring) tuned it, and it started right up no problem" so when you say no spring you only mean the part where the airbox meets the carb, not the spring on the needle right? Cause you definitely need the spring that is on the needle. Well I hope that you get it all figured out.

 

Wow thanks alot man, very helpful. Today I opened up the airbox, took out the filter and rode with it up and down the road with out the filter and cover on, and it was still just as slow, so its gotta be a problem with the carb. I backed out the air/fuel moxture screw a couple turns and nothing, just a slightly higher idle.
And yes I ment the spring that holds the boot on to the carb, but he also said he replaced the needle, i hope he put the right one in, and one with a spring, Ill have to take it apart myself and look. Ill try to see if that slide is working right too.

 

OH and if it is that seal up top like you said it might be, that thing is $100!!! thats crazy, unless i looked at the wrong part. I found it on this website:
http://www.powersportspro.com/...brand/9/Kawasaki.aspx

Part# 16126
Is that the right part?

 

That is the part I am talking about. If it has a leak that you can find in it, I would try some silicone sealant (just a light coat) before I dropped a hundred bucks on it. Also make sure that the choke is installed in the carb correctly. If you end up having to get a new diaphragm, I would just spend an extra 60 and pick up a mikuni 36mm kit from cycle works racing (he has a $160 36mm carb kit - stock is 34mm) Also you can watch ebay and pick up a whole carb for less than $100- any year of mojave 250 should work. But use that diagram on that site that you showed me or use the one on http://fiche.ronayers.com/Inde.../4005/Model/Mojave_250 and make sure that your carb is put back together right. Maybe ask your friend for your stock needle back and put that in. The air/fuel mixture screw, if im not mistaken, adjusts the mixture at idle so it wouldnt help when you are getting on the throttle. Let me know how it turns out.

 

i am at work but i will check it out when i get home later. Will the jets from my carb fit the 36mm one?

 

Alright I took off the boot connecting the carb to the air box off, and was throttleing the engine (while running) and the slide was not moving. So thats the problem, I just ordered the Minuki 36mm carb from cycleworksracing.net. He said he jets it and tunes it so thats pretty sweet. Is this carb have the vacuum suction thing too? Or is it different? Is minuki a good carb? will it last me a while? Thanks alot.

 

Oh ya, and is it safe to ride the quad as is, since the things not moving? Because I was supposed to go riding this weekend, or should I wait?

 

at worst you may run rich and get some carbon buildup on your head and could fowl up your plug, but it shouldnt do any damage to the engine. If you run lean, that is when it is dangerous. The mikuni carb doesnt have a diaphragm slide and it should be a much quicker throttle response (and overall more power). I am not sure if the jets will fit, but Greg should set you up pretty good. If you ever need more jets they are about 3-4 dollars each at almost any powersport dealer- and even cheaper if you buy more at a time online. Mikuni is a pretty popular brand of carb and unless something serious happens, it should last forever. They are also very easy to get parts for if anything ever breaks or needs changing, such as jets. Let me know if you decide to get rid of the carb and intake boot, I might be interested.

 

I put on the new 36mm carb from http://www.cycleworksracing.net/mojave.htm and the quad runs great now, it is amazing the performance I get from it now. Greg jetted the carb for my setup. The only problem I ave now is right from idle when i hit the throttle quick it gags like it needs more air or fuel right off the bat, he said try adjusting the air mixture screw and if that doesnt work its the pilot jet, i think he said pilot jet. I have messed with the screw and it is better now, but i think i need the new jet. How do i know whether to get a bigger one or a smaller one?