Maintenance & Technical > KX500 Original
Help With Revving High
blueoval:
Could use some help with a 2000 k5 that is stock except for Procircuit pipe and FMF silencer. After high speed and some WOT it will rev a little high like it is lean. Not crazy high, but just high. It will do this for about 15 seconds and then come down. If I lug it it will come down to an idle. It doesn't do this at low speeds. It starts in 2-3 kicks when cold, 1 kick when warm, idles good, runs strong. I ride at 1000 - 2000 ft above sea level and the temperature has been 45-55 degrees farenheit. I performed leak test as suggested and it held 7 inHg of vacuum for 15 min. I pressurized the engine to 6 psi and it held for 6 min.
Compression is 150 psi
Carburator Jetting: Main 168
Pilot 58
Clip (stock) 3rd position
Air Screw 1 3/4
Float 15 mm (by Clymer Manual)
Fuel is 91 octane pump gas and Golden Spectro at 32:1
This is what the plug looks like after stretch of WOT and immediately shutting down the engine.
Any help would be much appreciated! B.O.
DoldGuy:
B.O.,
Sounds like your bottomend is tight by your tests. This might be redundant info, but it sounds like you are running a little lean on the pilot circuit. Based on your settings (& that plug looks good) I would try the same riding condition & when you chop the throttle & it still is hanging on to some revs pull the choke lever on & if the revs immediatley drop, then you know it is a little lean. From there, try the air screw at 1/2-5/8 out and re test, if it is better at those settings, then go to a 60 pilot and re test again. Out of curiosity what Slide # is in there? Also keep in mind that a 32:1 mixture is a Heavier Specific Gravity then a 50:1 ratio & may need a tad richer setting.
Larry Wiechman:
Could this be as simple as a sticky slide?
Larry
Hillclimb#42:
Mine seemed to do this a little when i had the idle set too tight. Maybe temp drop has leaned you out a little. You are lucky to be out riding it. Freezin' Balls here. Almost too cold to work on them.
Friar-Tuck:
B.O.,
The pressure testing checks out the bottom end. That surely reasons out the seals and or case leak.
The other post in reference to the slide, there is a number stamped on it, lower number = less taper What the cut-away does is change the air velocity over the main needle jet.
The electrode and the groundstrap look good, get a light down where the ceramic meets the metal in the plug. That small ring is what you'll want to look at for burn color or "Mixture Ring".
http://www.strappe.com/plugs.html (I can find color photo's if you like )
The "choke test" is a great idea to quickly check need for more fuel. The 32:1 I think is what might be a little different as the majority of guys run a little less oil/fuel.
Not that it's bad mind you. Especially if you have alot of space to run WOT. Our jetting will seem alot leaner as we are putting more fuel thru the bike at 40 or 50:1 , hence a 52,55 pilot where as you might need a larger pilot to get the same amount of fuel through the engine.
"By the Book" @ 50deg with the correction factor of about 1.03 x 58 that would be 59.74 on the pilot (or a #60)
and with the same correction factor of 1.03 x 168 that would be 173.04 on the main (or a #173 main)
with no change on the clip position and the #7 slide (or all the stock stuff)
Now this is estimating around 50 deg F and 1500'
It looks like you would be right on at 70 deg or so with the pro circuit jetting specs. (KX500 168 58 N82M 3RD 7)
This is with the owners manual pgs. 86 & 87.
Just something to consider..
I'm not sure this is lean enough to cause that high idle hang or not.. :|
Hopefully some more guys will have more Ideas...
Tuck\o/
Apologies for the large photo below, I don't know how to resize it!
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