Help With Carb

[hughes]

Hey Guy's. My 87 500 is running the needle all the way down but still seems like I could lean down some more from 1/4 to 3/4 throttle. I checked Kawasaki's web site and their is no leaner needle for this year. But they offer diff. jet-needle which is the in some carb therms would be the high speed nozzle. The jet needle comes in these numbers. Factory R-0 and the options are R-2,R-4,Q-8,Q-6. Does anybody know whick is the leaner or richer jet needle numbers.

[Kawadougie]

What carburetor do you have?  The stock unit for an '87 was a 38mm roundslide Mikuni.

[hughes]

That's correct.

[Arigato]

You could always order a 39.5mm Keihen(sp?) that came on the newer ones.  Sudco or Carb parts wharehouse has them and you will have access to all the modern jetting specs plus more power!

[Kawadougie]

The 39mm PWK Keihin is great for motocross but a piece of dog s**t for the woods or trails.  I'm actually running a 38mm Mikuni on my 2003 Kx500 for that very reason.  Stock needle for the 38 Mikuni is listed as an R-0.  If you go to the Sudco site: http://www.sudco.com/catalog105/061-063.pdf  
It calls this series the "needle jet" which is quite a different thing.  What number does your needle have on it now?

[fcs]

"The 39mm PWK Keihin is great for motocross but a piece of dog s**t for the woods or trails. I'm actually running a 38mm Mikuni on my 2003 Kx500 for that very reason."

Kawadougie, you've hit on something I've been wondering about.  I'm running the stock PWK on my 1998 500, but would like to reduce the gas consumption.  Would the 38mm Mikuni improve the gas mileage?  What other advantages are there to the Mikuni?
Thanks in advance for the information.

[Kawadougie]

I really don't know if the Mikuni would improve your mileage.  I just put mine on and had a short ride last weekend and I'm still working on jetting it.  I've used this carb for years and found it very easy to set up and you can actually get a KX-500 to idle properly with it.    What I'm primarily looking for is clean throttle response on the bottom end.

[neverendingmods]

 What I'm primarily looking for is clean throttle response on the bottom end.

Hard to get from a smoker and keep H.P up there.   The pipe,reeds, and porting play a big role.  Primarily the pipe.    I agree mikuni is easier to work on and there is an abundance of info on Mikuni on the web plus great books.  But the 39mm Keihin can be cooperative.   I've got the idle pretty well set.  Once HOT, idles smooth for roughly 1-1.5 minutes.  Now the first 5 minutes of riding she wants to stall of course.   My biggest problem was getting the throttle cable not to twist tightly as I put the carb top back on.  Caused stalling and high idling.(drove me nuts) til I found after tightening the carb top to counter spin the cable housing afew revs.

[hughes]

Kawadougie, Yes the stock is R-0. I need to know if R-2, R-4 IS LEANER and what are Q-6 and Q-8 Richer jets?

[Kawadougie]

R-2, R-4 are richer and Q-6 and Q-8 are leaner

I checked it out at the Sudco site and here is the jet needle chart: http://www.sudco.com/catalog105/061-063.pdf

How is the rest of your carb set up as far as main, pilot, jet needle and slide?

[hughes]

Thanks for the chart. Main is 350, Pilot is 27.5, Stock jet needle clip in top needle all the way down, stock slide. Bike runs strong but still seems a tad rich 1/4-3/4 throttle.

[hughes]

Kawadougie, Are you running this same carb? I'm going to order an q-6. Let me know what you have used with this carb.

[Kawadougie]

I recently purchased a new 38mm Mikuni carb and am working on jetting it.  It came with a Q-2 jet needle (four steps leaner) and I found that it ran fine from 1/4 to full throttle with a 350 main but I had to turn the idle air screw all the way in to get it to run with a 27.5 pilot and it was pinging off the bottom.   I will try bumping up the pilot next time.

[hughes]

Keep me informed. With 27.5 pilot my my mixure screw is 1 1/2 turns. I tried the 30 and 35 pilot but I starting having low speed plug fouling. I need to turn on my GPS and check my altitude. It's not that high. I'll look into new jet needle here in a week or two.

[Kawadougie]

I ride mainly around 5000 feet here in the Sierras.  Hey, I found a free tuning manual online for the Mikuni 38mm VM carburetor.  Has some very cool stuff in it.  

http://www.mikuni.com/pdf/vmmanual.pdf