Carb Tuning - Sizing the Pilot Jet (DR-Z 400SM)

Example bike was a 2006 DR-Z 400SM, however the technique applies to nearly all carb bikes. If you are having issues holding the bit in the 1/4 socket then apply a small amount of bearing grease to the inside of the socket and it will hold the bit.

The fuel mixture screw is almost always mounted on the engine side of the carb at the leading edge of the float bowl. It will be sticking down in a post and the screw itself is recessed into the post.

[davetechme]

I don't suppose you could do a video with the sound difference while adjusting the fuel screw? Basically, I turned up the idle such that it sounded faster than it should be then I turned in my extended fuel screw. It never got to the point where the engine sounded like it wanted to die (I suspect my 25 pilot jet might be too big and the bike is running rich), but I found that 1 turn out made it sound the most crisp. Does that sound about right?

[MotorcycleProjects]

How does it run with just the one turn out. Any hesitation trying to take off? Any idling issues? Also, is it still stalking at stop lights?

[etyrnal]

why a fast idle? my bike naturally idles real slow but it starts easy, runs well at any speed, and goes like hell.. what's the day idle needed for?

[doctorash]

great video. I personally hate this bike (mine in peticular) but the info was very helpful

[MotorcycleProjects]

I can't remember if you had a full exhaust or just the slip on. Either way you should probably have the 25 pilot installed that came with the jd jet kit. 1 turn out sounds a little lean. I imagine that would pop quite a bit on deceleration, though using the extended mixture screw requires fewer turns than a stock mixture screw.

I tried to record the sound difference this weekend but the only DRZ I have access to is so loud the camera heard the same sounds the whole time.