my arctic cat 300 4x2 will idle but runs bad when i give it fuel if i hold the choke down i can rev it up but it runs really rough i replaced air filter and spark plug ,checked plug gap have cleaned carb twice and checked boot conections with wd 40 my dealer says no carb rebiuld kit is made , i must buy each piece individualy does any one have any suggestions?

 

Does it have a good battery with the correct voltage/amps? Some machines will run rough with a bad battery. Usually its the EFI models but you never know.

 

The choke on your 03 model I believe is a plunger type of fuel enrichment system. I have quite often seen the plunger get corroded with some green goo and stick move very sluggish. (could be why you have to hold the choke down?)

Checking your battery and charging system is always a good start to ensuring you are getting the proper spark (along with making sure you have the correct plug). Service manual says it should be an NGK-DR7EA gapped to 0..24-0.028 inches.

The main thing I look at is the color of the spark plug.
Light tan = good color
White colored = Too hot (usually means its too lean and I have not seen this, yet)
Chunky/Black color = Too Rich (usually means too much fuel not enough air)

Most common rich fixes I have used:
1) Air/fuel screw: (low speed fuel screw) should be 2 and 1/4 turns out for your machine.

2) Float valve seat: Check that it is seating properly and is clean replace if needed. You have probably done this already but doesn't hurt to check again.

3) High speed jet: Make sure it is unclogged. Its opening is so small I usually snip a strand of copper off my copper wire brush and run it through the jet. You can usually feel it push through or see it come out if you look inside the carbs throttle body opening. I then follow that with compressed air and carb cleaner or both.

4) Low speed jet: clean the same as the high speed jet.

5) Choke: Clean the choke plunger and make sure it moves freely when you operate its lever.

6) Valve tappet clearance: As a last resort you may need to check the clearance. This usually makes it hard to start as well but can also make it run poorly.

7) Fuel tank: IF you find any gunk in the carb remove the fuel tank and totally drain it and let it dry out over night. Also remove the fuel shut off valve and clean its intake screen. This may also be a good time to install a small inline fuel filter is you have not done so.

As far a "rebuild kits" go I am not aware that they make such a critter for an ATV like they do for an automobile. I am pretty sure you can buy a jet kit if you want o replace your jets or change them. But I think you would need to order the parts separately.

Hope this helps,

Swampy

 

hey thanks for the advice, i replaced carb to head boot cleaned carb and all the jets had the valves adjusted, but it still idels good then dies when i give it gas local mechanic thinks its a timeing issue. any help? thanks

 

mudslimgfool and swampyjunior have pretty much covered it , one other thing you can try is your thumb throddle free play it should have 1/8" to 1/4" inch throddle free play ; and you should'nt need any tool's for this adjustment !

the throddle adjustment cable is located on the right handle bar you just slide the rubber boot back far enough to were you will see a round plastic lock nut that should be tight again't the throddle cable to keep it from loosining up the cable free play , then just loosen the plastic lock nut and turn the cable adjuster clockwise or counter clock wise to obtain the correct freeplay using the thumb throddle to cable , i had to do this to my 2006 AC 400 FIS Automatic 4x4 just last week ; you should be able to loosing the plastic nut and cable adjuster with your thumb and index finger that's all i could think of for now i hope this get's you back on the trail's !

williebee........

 

I had a very similar problem with mine, this is what I posted to a similar thread. There is no "kit" for rebuild as you found out.

I had some rough running problems with my 05 AC 300 4x4, so took the carb apart, cleaned, even replaced the jets, needle valve and spring. About $15 for all the factory jets.

Anyway after 3 tear downs with the schematic in hand no parts were missing. turned the needle till it stopped then back either 1 full turn or 1/2 a turn, cant remember but its what a carb tech told me to do at AC.

After months of headaches, the machine would idle all day long perfectly, light smoke, give it gas it would bog down like its choked. i could slowly get thru all 5 gears but let off the gas and it would stall.

Eventually took it to the shop, $100 for a carb tear down, which that carb i would have eaten off of after i was done with it, it was the shiniest piece on the bike. Anyway he found a missing piece in the carb. If your carb is similar, it has the long needle that sits under the black diaphragm with a spring, where that needle goes down into the body it should have a small beveled piece that looks like a race in a bearing set. its made of aluminum i think. that needle should be perfect in that limiting the fuel giving it proper mixture, well with my small can of compressed air I blew it out and did not know it the first time i cleaned it. its the size of the smallest O ring u can think of. Its not part of the schematic at all. I hope this helps if u need more of an explanation Ill try, let me know.

my carb was a Keihn (or something like that)