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I had a problem with my '01 KDX200 dying on the trail during my last ride.

Got it started again only after changing the plug (old plug was black and wet)

Inspected the reeds and they look good.

I pulled the carb off don't see anything obvious, but confirmed my jetting parts are all set to stock:

needle: R1174K (3rd notch)
main: 160
slow: 48
air screw: 1 turn

I also have an FMF Gnarly pipe and noticed their jetting guide recommends a R1173L needle, and 1.5 turns on the air screw.

Does it make sense for me to swap out the needle to what FMF recommends, and turn out the air screw half a turn?

Have you tried adjusting the air screw before? Beyond that, look at a 45 pilot.

I think Fmf recommends dropping main 1 size and pilot 1 size when installing their pipes

Jason wrote:Have you tried adjusting the air screw before? Beyond that, look at a 45 pilot.

Honestly, I haven't.

I'm pretty new tuning carbs.

KDXohio wrote:I think Fmf recommends dropping main 1 size and pilot 1 size when installing their pipes

Here's what FMF recommends (below). They give a wide range on the main and pilot, but I'm at top of that range with a 160 main and a 48 pilot.


Main Jet
155-160

Pilot Jet
45-48

Needle
R1173L

Needle Position
3RD

Power Jet
N/A

Air Screw
1.5

Fuel Screw
N/A

The R1173L needle is a 220 needle & half a clip richer than the R1174K needle from the 200.

I would re-jet to 155 main & 45 pilot & see how it runs ( fit a new plug & fresh fuel & clean air filter ) air screw 1.5 turns out.

Next I would lower the clip on the needle to the 2nd position & see how that runs.

You may need to adjust things further if the air box snorkel or lid has been removed.

155 Main 45 pilot and 1.5 out are a good starting point then use the jetting guide from there if you need further tuning

cornishwrecker220 wrote:The R1173L needle is a 220 needle & half a clip richer than the R1174K needle from the 200.

I would re-jet to 155 main & 45 pilot & see how it runs ( fit a new plug & fresh fuel & clean air filter ) air screw 1.5 turns out.

Next I would lower the clip on the needle to the 2nd position & see how that runs.

You may need to adjust things further if the air box snorkel or lid has been removed.

Thank you Cornishwrecker. I forget to mention that the airbox snorkel has been removed (that was recommended by FMF).

I'm the second owner of the bike and all this, including the pipe were done by the original owner.

KDXohio wrote:155 Main 45 pilot and 1.5 out are a good starting point then use the jetting guide from there if you need further tuning

Thanks Kdxohio.

I've had a 'crash course' on carbs over the past 3 weeks, thanks to you guys, along with You Tube and Cyclepedia.

It's starting to make a little more sense, but I still feel like I'm over my skis on some of this.

Funny I basically had the same issue and same questions and took me about 2-3 weeks to get to the point that now everything is dandy minus the fact I have to go back into the carb and deal with fuel dumping out of the overflow vent. Most likely float issue. But either way these guys don't steer you wrong if you ask the right questions the right way ! Good luck !


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Sgt.harper48 wrote:Funny I basically had the same issue and same questions and took me about 2-3 weeks to get to the point that now everything is dandy minus the fact I have to go back into the carb and deal with fuel dumping out of the overflow vent. Most likely float issue. But either way these guys don't steer you wrong if you ask the right questions the right way ! Good luck !

Thanks Sgt.harper. I'm glad I'm not the only one. Happy to hear you got your issue straightened out.