Maintenance & Technical > KX500 Original

Jetting!!! Again and again and again!

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KXcam22:
Gabe,
  Been reading throught the past posts to remember what settings you are at: 155 main, 38 pilot.  Is your last ride results with the richer CGJ needle? Let me know. Cam.

gowen:
Cam, I believe so, but don't remember. Sorry, but I will take the carb apart. My YZ250's linkage locked up and I have to rebuild it and decided to check the linkage on my KX and saw that is was cracked and majorly worn out. So, I have a spare bike and took it off and am waiting on swingarm, linkage, and shock bearings. Also, had my throttle cable go out and my air filter... So, waiting on a few replacement parts which should be in tomarrow or so. Once up, I will write another report and do some needle swapping. Cam, I thought I was at a 148?? But, I forgot.. I'm sorry, I've been soo swamped with work I've lost it. Anyway, thanks for your help... But where did Kawdude go to?

gowen:
Opps, you are right, a 155, I think I'm on the CGJ needle. But I need to check. I think I will try Sudco for another needle.

Glenn_KX500:
I thought I'd post some info for you guys.
I just bought a '99 KX500 2 days ago and have some printed info on jetting. My bike has a new top end, entirely new cylinder (not resleeved), Revloc auto clutch, ect.

The info I have says my plug gap is: 32/1000
Stock jetting 168/58
Jetting set at 165/55
My factory manual says stock is 175/62  :shock:
I imagine that would be way too rich, unless you compensated by using a high needle position. The stock needle position is 3, indicating that's probably too much jet from the factory, especially for high alt.

I do know quite a bit about tuning from jetting multiple bikes over the years, as you go up in elevation you need to lean out the mixture. I am in South Texas, RIGHT AT sea level. 165 seems good, although I will probably move the needle up one position (lower clip position) to richen it up just a bit.

I've been doing research for a few hours on surging on decel where the engine will keep kicking even if the throttle is totally cut. This is a little bit dangerous if the terrain is technical and you're not going in a straight line.
WOULD GOING TO A LARGER PILOT JET SOLVE THIS PROBLEM?
Surging on the low end is a sign of being too lean, would simply swapping out to a larger pilot solve this issue?
I haven't had my bike for more than a few days but when I cut the throttle I want it to stay cut.
The only other issue I have with my bike is poor idle.
The plug it calls for is a BR8EG
It comes pre-gapped at .024
A wide gap like .032 is out of spec according to the manual and will draw a lot more energy from the coil for it to fire.
So what I'll do is I'll get a BR8EG and gap it out to the maximum suggested in the manual, which is .7mm - converts into .0275"
I'm hoping that will allow for a lower, more stable idle.

http://www.ngksparkplugs.com/apps/motorcycles/make4.asp?id=4269&type=reg

As for the hiccup/surging/kicking when the throttle is cut, I have a hard time believing that is something these bikes "just do", I know with 4 strokes they come calibrated lean from the factory and popping on decel is very common, richening up the pilot will solve that. Will richening the pilot on this bike prevent it from surging on decel?
Would turning in the air screw a half turn improve this?

It's too late to go outside and experiment, or I definitely would.  :lol:

gowen:
Hi Glenn, I have put about a month of research into getting the surges to leave. It is possible to remove the surging, first by running a fat pilot and by running a rich needle height. Those are your only options, I am not toying around with a Boyesen Rad Valve and a PVL ignition, I will find out how this effects the surging and what have you. I hope this helps, if you are surging, I would suggest bringing up the pilot until it quits or calms down, then start on the needle height. But you will sacrifice your idle. Idle will come and be strong when the jetting is perfect, but then you will have surges. The big CR does it slightly also. Anyway, hope this helps, ask away at the questions if you want specific answeres. KXCam should be around soon too, he is the expert in this area. Thanks

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