I've owned my '98 400 Xplorer for about a month, and last week it suddenly started bogging when I give it full throttle. If I put the choke on, it runs better full out but won't idle worth crap. I took the carb apart and it seemed fine (the main jet is 180) so I moved the clip on the needle from the second position from top to the fourth position from top - but it didn't seem to make a difference. I also tried it with the air filters removed, but have the same problem. I checked the vent hoses, and they all seemed fine. I guess the problem lies in the air/fuel mixture because if I block off 2/3 of the air intake, the machine runs better. Oh yeah, I intalled a new spark plug as well. Any help?

 

sounds to me like you need a 230 main jet.that is whats in my stock 400.you will blow it up cause it is too lean.

 

180 does seem way too lean. If memory serves me...I have either a 210 or 220 in my 1998 Xplorer.

 

Bilbo,

Where do you live? The reason I ask is because if you live at high altitudes then your main jet should be a little smaller than stock. Where was the quad ran before you got it?

The stock main jet should be between 200 and 240. A 180 main is probably to small unless you live high on a mountain. Have you checked for air leaks? I've seen boots rip and suck air causing the same problems you are having. It just seems like something happened if it was running OK then all the sudden started doing this. Running your engine lean enough that it loses power is a real bad thing. Your engine will surely "melt down".

 

change your main jet to 200,then try it out at FULL throttle turn the engine off check the spark plug color,for the needle run it a mid-throttle turn the engine off...
this is the better way to run your engine properly.

 

If it just suddenly started doing this, check for restrictions in the fuel line, as well as the gas tank vent hose.
If it is bogging, and you loosen the gas cap, and it takes off, it is DEFINATELY the vent hose plugged or kinking. This is all too common. The hose usually has a dip in it that dirt accumulates until it cuts off the air trying to get in, and you vapor lock.