Maintenance & Technical > KX500 Original
Jetting!!! Again and again and again!
alan:
If the dyno was at the same altitude you going to be riding bike at!
I think dyno's are better suited for looking a power curves and hp!
What would be nice would be EGT Exhaust Gas Temp gage so you could tweak your engine, just like you do in an airplane!
Alan :wink:
Zee:
Hi All
Here?s my stats; 2000 KX500, Pingel petcock, 5/16 fuel line, rebuilt carb, float height set to 16mm and verified with homemade fuel level tube thingey, clean air filter, pilot 55, air screw 1? turns out, DEF jet needle in the 2 position, 170 main, it?s a little rich for now, but will adjust after I get the idle/needle jetting right. Elevation 1400 to 2,000 feet, temp???? My thinking at the time was ?I got the pilot jet dialed in so on to the needle diameter?. First it had a N89D, way too lean just above idle and way too rich between ? to ? throttle! Bike only ran good at WOT. Couldn?t find data on this part number so I switched to Sudco as they have a nice chart that explains what the numbers mean and at $5.25 a piece who would argue. They recommended a DGH; Bull?s-eye, HUGE improvement! Bike never ran so good but surging was also huge. As soon as I?d chop the throttle bike would go into the ?surge mode? maybe 15 times before enough speed was lost and the motor was back to idle. But I new I was on the right track as performance was unbelievable, (I hope you believe me). Next; 58 pilot. Way too rich at idle with 3 ? turn out on the air screw and it didn?t? help the surging at all; switched back to 55 and 1 ? turns out. Next; went smaller in the needle diameter from the DGH to a DGG. This cut the surging in half! That inspired me to again go to a smaller diameter needle. Only problem is no one makes a DGF, had to go with a DEF to get the next size smaller diameter. While this is one step smaller in diameter, it is also two clip position shorter in the functional L1 length. So what-the-heck I thought I would try it any way. Installed it in the middle position, (3), and went riding. Surging was reduced but not as dramatically as the ?DGH to DGG? needle change. Also caused bike to start running rich, (rough), in the 1/3 throttle range and a drop in needle position helped some but still feels like it?s too rich. Okay that?s where jetting is at today and I?m planning to drop the needle again to the one position, (hope it doesn?t need to drop further as I?m out of position). Are you still with me? My question is what needle are you running on your stock bike? Gowen and KXcam22 helped me out by answering a question I had in another topic, ?who makes custom needles?, answer; JD jetting. But what got my curiosity was a reply that I?m out there on the jetting and the fact that the direction I?m headed is running out of needles.
gowen:
Zee, this is how I went about jetting my bike: #1...
Pilot-
Unscrew the pilot screw until I got most idle. If the airscrew was more than 2.5 turns out, I replaced with a smaller pilot jet. I did that until I got the maximum idle. Then I moved to the needle. I did that by the seat of my pants or.. dial a wheelie (most wheelie power 5th gear). If I was at the top of the needle, I'd go leaner, if I was at the bottom of the needle, I'd go with a richer needle. I kept doing that until I felt good about it. Then moved to the main jet. I kept going down until I got a CRISP rev when hitting the throttle. Also, until the smoke cleared. Take it for a few laps WFO. Keep going down on the main jet until you get that perfect hit,clean.
Continues next post:
gowen:
Continued:
I drag race my KX500 in hillclimbs and drag runs. My KX surges pretty bad. That is normal! That is saying your jetting is right on. Don't worry about the surges. Cam and I have decided that surges are a sign of your jetting being close. I can say my jetting is perfect now, but it costed me a year or more to get it right.
Also a trick for the mainjet is to warm your bike up, do a FULL on wide open throttle test with a BRAND new plug. pull it out and look at the color. Brown is good, any grey or black indicate it is too rich. I pull my plugs out now and I have a hint of richness now, but mostly brown. NO black. But that is due to me running it rich due to the systems I am running now.
Good luck and let us know if we can help.
KXcam22:
Zee,
Sounds like you know what you are doing so it should be quick to dial your bike in sweet. You'll know when you are there when the powerband suddenly get super smooth, the dial-a-wheelie and your bike will start 1-2 kicks hot or cold! First some more data.
1. What is your average temp & humidity and you say about 2000' where you ride.
2. What fuel/oil do you run and at what ratio.
Also one thing to note is on the PKW39 the main and needle overlap quite a bit in the 3/4-full throttle range. Before you can really get the needle exact you need to narrow the main jet down. The 170 will be rich and will affect your needle testing as low as 2/3 throttle and up. As Gowen suggests you would be best to get the main dialed before you proceed. Then after we help you find the right needle it's best to do a double check on the main. Gowen's plug run advice is exactly the way you want to do it. I usually try to find a bit of a hill to put some load on the engine. Also the surging thing seems to be a sign that your jetting is on. Mine is the worst offender but I don't notice it anymore, I just keep the throttle mostly open all the time!! The jetting chart is really close. I arrived at my jetting after years of tuning and it matches the chart. I would suggest using the chart setting as a starting point and then we can fine tune the needle. I'll analyse where you are with the needle right now and post back. Cam.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version