Maintenance & Technical > KX500 Original
Jetting
littlewing78:
I recently got a new top end and now my bike is running too rich. It is a 99 KX 500. It runs great but smokes a ton and a new spark plug will be black after one ride. I checked out the jetting chart to see what is recommended. So I took my carb off to see what I was running. Maybe I am reading the jets wrong but the number seem to be way off compared to the chart.
The needle is right with an N82M. It was on the 3rd clip so I moved it to the 4th. Didn't seem to make a difference.
The Main jet has what looks like a check mark and then a 48. Maybe the check mark is supposed to be a 1.
The Pilot jet is 85.
I have the air screw at 1-1/2 out.
I am not experienced with this at all but those numbers don't even seem to be in the ball park. Everything is stock except for the new wiseco piston.
I run 91 octane pump gas at 32:1. And I am at 5000 ft. Any suggestions? Thanks
alward25:
Wow a 148 is way too lean and an 86 pilot is way toooo rich. 165- 172 main and a 52-58 pilot is pretty standard If the rest of the engine is in good shape that should put you in the right neck of the woods. The bikes that run at the salt flats in Utah usually run a 165 main and a 55 pilot of at least in that neck of the woods. I know there some higher altitude guys around that could chime in.
Polar-Bus:
--- Quote from: littlewing78 on April 25, 2011, 03:45:39 PM ---I recently got a new top end and now my bike is running too rich. It is a 99 KX 500. It runs great but smokes a ton and a new spark plug will be black after one ride. I checked out the jetting chart to see what is recommended. So I took my carb off to see what I was running. Maybe I am reading the jets wrong but the number seem to be way off compared to the chart.
The needle is right with an N82M. It was on the 3rd clip so I moved it to the 4th. Didn't seem to make a difference.
The Main jet has what looks like a check mark and then a 48. Maybe the check mark is supposed to be a 1.
The Pilot jet is 85.
I have the air screw at 1-1/2 out.
I am not experienced with this at all but those numbers don't even seem to be in the ball park. Everything is stock except for the new wiseco piston.
I run 91 octane pump gas at 32:1. And I am at 5000 ft. Any suggestions? Thanks
--- End quote ---
Are you kidding me a #85 pilot ????!!!! How the hell does that 500 even start let alone run without immediately wet fouling the sparkplug ? That is SO pig rich, no wonder the bike smokes so much. I normally don't like to give out my jetting but in this peticular case I will. Keep in mind my jetting should get you in the ballpark, I am NO jetting guru, but my 500 runs perfect with this jetting. You might need to fine tune a tad richer or leaner to compensate for air temps. This should be a decent baseline for temps around 65F. Try this :
#165 main
#55 pilot
stock needle in clip pos #3
air screw 2 turns out from closed
If after this your 500 still runs bad you need to do a compression test. Make sure your compression is up around 160 psi . DON'T "assume" because you have a new top end that the compression is good.
Motorrad:
Before you go changing things...
I always tell people... What was the last thing you touched?
In otherwords..
Did it run fine before the rebuild? or is this a new thing its doing only since the rebuild?
littlewing78:
Thanks for sharing your top secret formula with me Polar. The bike isn't running bad at all. It runs just as good as it did before the new top end. It's just noticeably richer now. I have had the bike since last august and have yet to foul a spark plug either. When I first got the bike the air screw was set at 4-1/2 turns out. Thats really the only change I made other than the top end. Thank for the advise. I'll get those jets and see how it does.
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