no load miss???

[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

[Friar-Tuck]

  HC 42
 Am I not understanding his post clearly?  The bike has to be run up to like 1800 or 2000 rpm to take off?
    Tuck\o/ 

[seff23]

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/ 

no this is a 94 with a pwk, i just had the top end done when it had the seals so maybe 8 or 9 hours on that, power valves are working good, its been doing it since before the seals and top end, i'm thinking that its got to be too lean for it to surge when you try and accelerate in first, but i dont know why it wont do it in any other gear,

[Hillclimb#42]

Seff23's saying that when his bike is not under a load its not a steady rev, I think. Its good under a load like on the Brap, but not so good in first gear on an easier throttle.

Sounds like a air screw issue to me, or a needle position. Could be a number of things, but realizing its a trait from before rebuild narrows it down a little.

[seff23]

Seff23's saying that when his bike is not under a load its not a steady rev, I think. Its good under a load like on the Brap, but not so good in first gear on an easier throttle.

Sounds like a air screw issue to me, or a needle position. Could be a number of things, but realizing its a trait from before rebuild narrows it down a little.

yeah thats it i tried to go up one and down one on the needle and its the same either way, so you think i might need to play with the air screw then? i know the silencer needs to be repacked you think that might be some of the problem?

[Hillclimb#42]

I am really not the tuner. I like chiming in, but just guessing. I have seen silencers cause issues when they start to clog, but not sure what happens with too much oil saturation. If its trying to clog up in there, it will definately take away power. One way to find out if thats it.

[Friar-Tuck]

 Seff,
 I have seen silencers cracked and broken inside and the packing will actually be hanging loosly in the canister.
    If there is enough "hanging" in the pipe center it's just like stuffing a rag in the exhaust or holding your hand over it.
 If this is the case, getting the rpm's up enough to overcome the resistance could be part of the problem.
     If the silencer checks out, we can work on that off Idle to 1/8 or 1/4 throttle.
   
Off Idle to 1/8 your working mostly the pilot and airscrew.
   You say you don't have any trouble getting her started or to idle. 
That would indicate you are close on the pilot.
  as a general rule  More than 1-1/2 turns open on the air screw usually means you can drop one size on the pilot.
   (that will lean out the whole range of that circuit.)
   Less than 1-1/2 turns indicates you need to richen up the pilot (as less turns on the screw allows less air to mix with the fuel drawn through your pilot circuit)
   
  The Clymer I have pg 336 table 6 says stock jetting is
Main 168
Slide cutaway 7
Jet needle N82M /3
Pilot #60
Air screw  (Turns out) 1-1/2
Float height 15-17mm
Fuel level 0-2mm

 Do you know what pilot you have in the bike?   

   I'll try to get some more jetting  explanations in my gallery .
http://www.kxriders.com/coppermine/displayimage.php?album=lastup&cat=11045&pos=0
 Tuck\o/