Hello fellas. The forum looks great. I am having a problem with my 07 arctic cat 400. I really need some help figuring this out. What I have done so far...

-Cleaned the carb. several times.
-Checked the amount of fuel goig to the carb.
-Air filter and all vaccume hoses are in good shape.
-I am getting a spark.

The atv idles fairly well and handles high rpm well. The problem is from idle to 1/4 throttle. The secondary jet worked fine for years and is clean, so I don't think it is the jet. After running for a few minutes I can pull the plug and it is black. Dry though, not like flooding out. If I am correct, the adjustment screw gets only a 1 1/8 turn out. Where should I go from here? Thanks in advance.

 

Update. I am continually looking for the answer on the internet. I have a few more ideas from searching but I need a little help. Next thing to check... is the choke working properly. This model has an electric choke. How do I test it using a multimeter.. or is there another way? If the choke is allowing to much fuel to pass into the venturi... can I adjust the air up to match and have it run decently? Next idea is a weak spark. Can someone link me to a good tutorial on how to use the multimeter to test the plug wire, coil, etc. I have found a few "how to's" but nothing really good. Any help is greatly appreciated.

 

When you say cleaned the carb, several times, did you take it apart and use carb cleaner and compressed air to make sure all passageways are clean? it sounds like the pilot jet is plugged, the only way to to clean it is to take the bowl off the carb and remove the jet, air screw should be 2 to 2.5 turns out, not familiar with the electric choke, should be able to run motor and choke it to see if its workin

 

Welcome to the forum
First of all the spark plug color being black is a sign that your air/fuel mixture is to rich , spark plug should be a tanish brown , a white/grey color means your air/fuel mix is to lean , black means you're to rich , tanish brown is perfect , i agree with kerbbirds about removing the carb and giving it a good cleaning to insure that no jet passages are plugged !

I have a 2006 Arctic Cat 400 FIS Auto 4x4 (my first new quad) it has the electric choke/enrichner carb. , my 400 was a little on the lean side when new something all manufacturers do to help pass USA EPA emission standards ; i've never had a problem that
required the need to remove my carb for cleaning.

But i did have trouble with the choke/enrichner whitch turned out to be the cheap hard plastic fuel hose that comes standard on all the new quads now days , it was the one that hooks to the fuel filter located under the seat and goes to the carb , it started seeping gas from what looked to be where the hose was clamped the the fuel filter ; i was showing it to my brother - inlaw afew days after i first noticed the leak.

It only leaked while the engine was running and while i was wiping the fuel from around the hose clamp James ( brother-inlaw) ran his finger up the hose and he told me it was leaking higher up the hose instead of where it was clamped to fuel filter , i leaned one to get a better look just in time to see fuel spraying from the hose where it was routed around the air intake tube ; this was causing the choke/enrichment pump lever to stick when i pressed down on the lever ( it's suppose to come back up ) as pressure from the fuel pump feeds to pressure for the choke !

After replacing the hard plastic hose with Automotive Goodyear rubber hose and clamp's my problems were solved , this may or may not be your problem you're does sound like you need to remove the carb for a good cleaning like kerbbirds has suggested ; one you get the cleaning done and your problem fixed i would suggest that you get a can of SeaFoam from your local Auto Parts Store and mix some with your fuel !

The SeaFoam will keep you fuel fresh longer , clean your intire fuel system , clean and prevent excessive carbon deposits in your combustion chamber ; whitch also be a big part of why your spark plug is black i hope this help's you get your quad going like new again !

williebee.......

 

Update:

Maybe I am missing something. The sticker on the frame suggests 1 1/8 turns on the air adjustment screw. I am at 2.5 turns and still the spark plug is dry and black. Idle is good with a miss now and then, high rpm's are good. Up to 1/4 throttle it misses and dies.
I have been searching at arctic cat parts (.com). I notice that there is a washer and a o-ring before the spring on the adjustment screw on the parts diagram. Can someone verify this? I do not have the washer or the o-ring.

Its obvious that I have a problem with the secondary jet even though its not clogged. (washer and o-ring missing maybe) But it also sounds like the electric choke is sticking, allowing to much gas. I am guessing and desperate. Waiting for advice.. thanks much guys!