[johnsmith2]

I had problems with my 400ex idling after going to the dunes, so i get a carb rebuild set and i cleaned it and replaced what looked worn after i do so i start it up and it was backfiring or hiccuping through the carb and it died every once in awhile. i messed with the A/F screw it helped a little, Is there something wrong with the carb or am i not adjusted correctly.

 

[Goober]

Backfire is a lean condition check to ensure you have the carb secure on the engine intake boot.

 

[SlammedRanger]

Welcome to the forums!

A hiccup through the carb is generally a lean mixture or pilot jet symptom. Alot of time it can also be a stretched timing chain along with the lean tuning. I have found that everytime i change the timing chain it almost always goes completely away. The stock 400ex timing chain is very weak and stretches on every one i have ever seen from just normal riding. The crf450 chain is the common upgrade. Its thicker but fits in with zero modification. I have one in my quad and everyone i have ever built. My .02

 

[TRX2fiveO]

Change the slow to a 42 and back the fuel screw out 1/4 turn. Hiccup solved