Maintenance & Technical > KX500 Original

no load miss???

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seff23:
i'm having trouble figuring out whats up with my jetting, it idles good, it starts good, its plugs look good its got brand new seals maybe 8 or 9 hours on them, the problem i'm having is if i'm in first and i gas it hard or roll on it easy it breaks up. but if i shift it to second and gas on it or roll on it easy it pulls hard and clean, it only seems to do it when there is little to no load on the motor, and i thought it was the reeds but i checked them and they look pretty good, so i'm kinda stumped on what it is, so any help would be awesome. thanks!

Friar-Tuck:
 Hey Seff,
    If you could give us a little more info we may be able to offer a few suggestions. 
 Temp, rough altitude, mods to the engine, pre-mix ratio, current jetting etc. 
    Off the cuff if everything else seems to be o.k. I would start with the needle.  If the bike seems to take off at after
   around 1/4 throttle.
     Tuck\o/

seff23:
ohh yeah sorry. i'm in florida so i'd say about 50 feet above sea level, it dont matter the temp hot or cold or if its just been started or if its been ran awhile, i run 93 with maxima 927 mixed at 40:1, its been ported for low end and has the older style power valves with out the center flap, has a pro circuit pipe and silencer. its got a 168 main and the needle is 2 up from the bottom, 1.75 turns out on the air screw

Friar-Tuck:
Seff,
 Is this the 91 500 with the PJ carb?
   Since the choke and Idle are on the same circuit, it could be messing with you.     
          You could easily raise the clip on the needle. that should start to lean you off Idle. 
   If you do get a chance to move the clip, write down the needle I.D. numbers and or letters.
   We can have a look at the chart and see where that needle taper is. (just another piece of the puzzle)
        The other thing you will want to check is that the power valve is in fact moving nicely.  If that is stuck it may also be messing up the bottom end. 
 I put some links on a recent thread in the jetting area that might help.
     https://www.justatv.com/pages/keihin_pj_parts_diagram/pj_par6.gif
  The next time you have the carb off measure the engine side opening, that will tell us the size and what stock jetting was, just for some kind of baseline.
      Tuck\o/ 

Hillclimb#42:
What was looking "pretty good" about the reeds? They need to be sealed and no broken corners for low end response. Mine ran that way on Boysen Rad valve, but was a constant trait. Is this a new problem?
You can always start off in 2nd 8-)

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