KDXRIDER.NET

Hi all!

I went on a local trail ride here in southeast Idaho and had some difficulty with my bike bogging. The specs of my bike are
2002 KDX 200
Air box lid removed, Gnarly woods pipe
42 PJ
148 MJ
Needle 3rd clip
Air screw 1.5 turns out
Temp was around 60
Elevation was 5,000 - 8,000 feet

Before the ride I was riding around my house in 3rd gear and when I would get on it, it would bog bad right at first and then clean up at higher RPM's. When I start the bike cold with a choke on it likes to rev pretty high for about 15 seconds and then idles back down.
On the trail as we climbed higher an higher my bike would get harder to start and would start bogging pretty bad in the low RPM. I would have to rev it pretty high and feather the clutch to get it going once we got really high! (7,000 +).

This is where I get confused. I thought bogging was attributed to being lean but the bog got worse at higher elevation. When I was up there I tried running with the choke on but it didn't run at all with it on. So im guessing I'm still rich on the pilot or needle position?

I just did a topend and replace the reeds a couple months ago and clean out the carb. I also replaced the jet block gasket.

Could it also be that I'm jetting correctly and my bike doesn't have enough power at that elevation? I had to feather it quite a bit my last hill climb and I was in first gear and I only weigh 140 lbs.

Any ideas?

Thanks,

Austin

could be that your crank seals are leaking and causing a lean mixture

Sounds like a rich bog, not lean. You have to much fuel and not enough air, as you climb the air thins making this worse.

Jaguar wrote:could be that your crank seals are leaking and causing a lean mixture

I took off my stator cover and it's dry as a bone in there... don't know about the other side.

6 Riders wrote:Sounds like a rich bog, not lean. You have to much fuel and not enough air, as you climb the air thins making this worse.

This is what I thought... though I always heard that a bog meant it was lean. That's why I'm confused and how do you tell from a lean bog or rich bog?
I have a 42 PJ and a 148 MJ already and am nervous to go leaner.

"it likes to rev pretty high for about 15 seconds and then idles back down"
that sounds like an air leak (seals, base gasket, frayed reeds)

Jaguar wrote:"it likes to rev pretty high for about 15 seconds and then idles back down"
that sounds like an air leak (seals, base gasket, frayed reeds)

It only does it when the engine is cold and the choke is on. After it warms up there is no high rev but is can sometimes be a little hard to start when warmed up at altitude. I looked at other forums and they had said its normal for bikes to rev slightly high when cold.... but maybe its not. :(

My bike idles a bit high when cold too and the pilot is dead on.

Maybe i will try a leaner pilot and see how it goes

Yes I would say a smaller PJ will help, try to do it following the jetting guide (it really helps sorting out the PJ size)
I have very similar spec bike and riding in similar conditions and I'm running 38, 152, 2nd clip - jetting which is 10% off from perfect, still slightly rich in midrange.

Searle7,
I have an '04 KDX220. Mods include airbox lid top cut out, FMF Gnarly pipe and silencer, Twin Air Filter, V-Force 3 reeds. I ride in the 6,000 - 12,000 altitude range. My jetting is 38 pilot, air screw I can adjust with my fingers (very important to get air screw correct), needle clip in 3rd slot from top, and main jet 138. The effect altitude has on throttle response is not insignificant, and smaller-bore motors like these are pretty sensitive to jetting.

Your pilot seems fine ...I would try the needle in the 4th position from the top ....if it's slightly better then go up a size on your main jet ....you may need to go up on your main x2 & try your needle back in the mid position .