I have a 99 xplorer 400 and a couple of years ago this problem showed up. The machine starts, idles, and runs great, unless you hold it WOT for several minutes. The engine cuts out on you as if you ran out of gas. If you leave it alone it will stay idling and after about a minute you can got WOT again for another minute or so. I am assuming the bowl is dry after being WOT for several minutes and I just need to wait for some gas. I have tried with the gas cap off and this still happens, the vent line is clear.

I have replaced all the fuel lines, fuel filter, rebuilt the carb, new spark plug and it still is happening. I even tried going up one size on the main jet with no help. I have a K&N filter and it has been recently cleaned and oiled. I got the problem to go away for a little while after pouring some gumout in the gas, but a few months later it came back. I still think the problem is in the carb, but I don't know what to try next? I tried some seafoam this year with no help.

 

did you try to adjust the float level? sounds like it is calling for more gas then is flowing though the float. maybe even looking at the needle and seat to make sure it's not deformed some how. just a thought.

 

It sounds like the same thing my machine is doing, I havent figured it out yet myself. Keep us posted and if I figure something out i will let you know...

Fire3096

 

First thought was fuel filter but since you said you changed that, have you checked the screens/fittings inside the fuel tank? My 97 Sport had metal screens inside the tank which were in bad shape when I bought it. Good luck...

 

It could be a crack in the coil. Make sure the fuel inlet into the carb flows gas all the way through into the bowl. If there's anything in that passage it will slow your fuel flow down. Or just dump that tank of gas into a pan and check it then refill with fresh from another station. I've gotten gasoline that was so bad that a pushmower woulnd't run on it. just my 3 or 4 cents

 

did you gap the plug when you put a new one in? I believe its .018