Air Screw adjustment observation

Joined
Dec 14, 2002
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#1
I thought I would pass along my experiance and observation when adjusting the air screw (AS) when riding at various elevations. Feel free to jump in and comment on your experiances as well.
I have a 1999 KDX220 with weisco piston, air box lid removed, VFII reeeds, FMF -35 pipe and SAII.
I have noticed that when I change elevations, that I need to turn the AS counter clockwise about 1/4 turn for every 1000 feet of elevation rise. I really notice the performance increase when there is a long uphill and I have to chop the throttle to make a turn mid-mountian. At that point, my rpms drop as my speed decreases so I can manuvuer the turn, then when I exit and get back on the gas, the engine bogs a little. I don't want to shift because at some point I will need to upshift again and will loose my forward momentum. By keeping my AS set for the proper elevation, I can get the bike to pull strong at the lowered rpm's without bogging down to a stall and not needing the clutch.
I mention this because my riding partner has traded his KDX to a KX500. That thing has stock about 63 hp so he never hardly shifts on hills and turns anyway. So I was thinking that maybe an upgrade to a larger engine might be in my future too. With this simple adjustment, I can keep the low rpm end of my hp range at it's peak. A side benefit and another way to determine if the AS is set right, for me anyway, is that my bike is hard to start if shut down warm for a few minutes, then I try and restart it. Like when you are waiting for someone to catch up or you stop to check your map. It takes many more kicks to start if the AS is set too rich. When I adjust the AS out (CCW), to increase air mix, the bike starts much easier.
Anyway, I thougt these observations might help someone else out there with a KDX220 thinking they need to trade up to a larger engined machine.
 
Joined
Sep 7, 2005
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#2
Thanks for the tips. I have '01 220 that I keep thinking is down on power down low. It may be the air screw. When I'm climbing long hills (Clear Creek) the bike will bog, if it loses some RPM's.
 
Joined
Sep 7, 2005
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#4
76GMC1500 said:
Clear Creek, huh? How is the riding out there this time of year? Too slick?
Pretty good. Some parts may be dusty(not much rain this year), but you can find other trails that aren't. It can get cold overnight, if you are camping. I've only been there a couple of times, but we did some really fun single tracks.