Will not accelerate 2003 Kawasaki KLX 400 R

SOURCE: choke on

Sounds like your idle jet is clogged. This is caused by gasoline evaporating out of the carburator during long periods of disuse which can leave a varnish residue. You will probably need to remove the float bowl and remove the jet to clear it as carb cleaning additives in the gasoline are usually useless for this problem. It is vital that you use the exact fit screw driver on float bowl screws as they are usually very tight. The jet will have a very small opening and you could damage the jet if you use the wrong method to clean it (do not use a drill bit). First try a carburator cleaner spray with the small plastic straw that comes with them. Look thru the jet hole by holding it up to a strong light to see that it is indeed clogged. Then try holding the small straw in the jet orifice and forcing the cleaner into and through the jet. Be careful that you don't deflect the spray back into your eyes. Use eye protection. You could try to soak the jet in a cap full off the cleaner for a while. If that doesn't work a very small stiff wire might work to push the clog out (from a wire brush?). Then try the spray method again.

SOURCE: 2003 KLX 125: how fast do 2003 kawasaki 125 KLX go...

Should do around 55mph at wot in 5th gear with an averge sized person on the bike.

SOURCE: what should the valve clearence be on a 2003

Clearance should be 0.10mm-0.20mm (0.10mm-0.15mm for hot cams)
same as the drz, intervals are supposed to be 14,000 miles but I used to do mine at less than 10,000
hope this helps!

SOURCE: my klx 400 stock carb

check and clean the carb, there must be a dirt or an small object blocking the intake line of carb causing to malfunction the fuel floater. the floater acts like a control switch when the fuel reservoiris already full the floater floats causing to shut of the fuel.