2003 Arctic Cat 400 4x4 gasping at high rpm

[AvidCatRider]

My Cat sounds like it is gasping for air at high rpm's. Idles great and runs strong to about midrange on the throttle and then sounds like it is choking out. Fresh plug, clean air filter, cleaned the jets, float is good. Runs better but not perfect without the airbox cover in place?????? Checked the "snorkle", all clear. Any ideas?

[swampcat07]

Does it have an aftermarket exhaust on it?

At what position of the throttle does it start gasping? 1/4 to 1/2 1/2 to 3/4 or 3/4 to full?

What is the elevation of your riding areas? Do you go from the low elevations to higher ones? ie +/- 2000'

Let me think about this one. It almost sounds like too much fuel so it was either jetted for a higher elevation or colder weather.

[swampcat07]

Also when you were running it without the airbox lid was the filter still in palce or did you remove that also. Could be a dirty air filter.

[AvidCatRider]

Stock exhaust, stock factory jets. Starts gasping around 1/2 to 3/4 throttle, closer to 3/4. I am essentially at sea level. I have had the quad for about 5 years, this just started happening when I fired it up over the weekend after it had sat since summer. Gave it the mini-tuneup, cleaned the jets and checked the float to try to resolve. I have run it with and without the air filter, no noticeable difference... but as soon as I put the airbox lid back on it becomes noticeably worse, even with no air filter in place. I agree that it seems like it is running too rich, almost like it wants to really open up more than usual if it could just pull more air. I am really baffled. Thanks for trying to help.

[swampcat07]

I have seem cases where the diaphragm is work or reinstalled incorrectly. Let me think about it while I am out in the garage this weekend, and I will have a chance to pull up your parts diagram.

On my 07 there is a vacuum line to the carb and if there was a pin hole or loose connection it would not pull enough gas into the carb.

[swampcat07]

I looks like the gas is gravity fed looking at the parts diagram. But there still may be a vacuum if you look at the nipple mid carb, not the one on the top for the gas. I looked at the engine breakdown and couldn't really find where it goes to. On the newer models it goes into the boot between the carb and the engine.