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I have been trying to cleanup the off idle richness and spooge on my 04 KDX 200. Stock pilot was a 48, which has been changed to a 42, 40, and now a 38 which runs pretty good, but still 3 turns out on the air screw. With this setting there is no adjustment remaining when going up in altitude.

Bike setup as follows:

3200' elev.
155, R1174 middle clip, 38 pilot-3 out , 40:1 HP2
Stock pipe and silencer (need quiet due to neighbors)
Recent power reeds (which required richer main and needle settling/ leaner pilot)
Air box top removed
+- 75 hrs on original top end
BR8ES, medium brown at low to mid where it is ridden most.

So is a 35 feasible or could the exhaust, power valves, rings, be something to check into first..

Have you checked the jet block gasket?

Jet block test like SS mentioned and also change your float level to 18mm instead of 16 if that's where it is currently. I had to go down to a 35 and still had no room to play with the air screw when my floats were at 16. Changing to 18 and redialing everything in and I ended up with a 40 pilot at 1.5 turns out.

Yes, recently changed the jet block gasket and it appears the original was good also - no difference.

I lowered the float level a while back when it occasionally leaked out the overflow on the kickstand. Which way does that go again, when the floats are too high, or too low it richens the pilot circuit?

As a note I tried a CEL needle and that made the situation worse off idle. What I should say is when the throttle is just opened its not smooth, could be at 4000+ RPMs like slowly getting back on the gas at speed, wicking it is fine.

Time to do compression and leak down tests.

I may just do the top end, interested in the RB setup as well. Unfortunately their website says they are booked right now. Trails are closed up here in July so maybe then.

The Stock exhaust and cut air box are the only other things I'm considering. The older models had jetting issues with this mod if I remember right.

If you're looking at the carb installed on the bike, an 18mm float height would have the floats hanging further down into the bowl than 16mm. 18 leans out the mixture vs 16.

firsthere wrote:I may just do the top end, interested in the RB setup as well. Unfortunately their website says they are booked right now. Trails are closed up here in July so maybe then.

The Stock exhaust and cut air box are the only other things I'm considering. The older models had jetting issues with this mod if I remember right.

Well, a leak down test will help diagnose other issues that could be affecting jetting and other things even if you plan to do a top end.

No jetting "issues" other than normal jetting changes when making modifications to your engine.

What type block off plates do you use for the intake and exhaust?

Here's the one I made from ace hardware parts and I already had the blood pressure bulb. You can also use a schrader valve in its place but don't pump the engine with an air compressor. The tester goes in the intake side and an expandable plug (marked 1 3/4") from the auto parts store blocks the exhaust port. I've read that the piston should be at the bottom of its stroke for a leakdown test and that's they way I've always done it. Good luck with the bike.

Thanks, very nicely done!

What puzzles me is how a leak would cause a rich condition. It would seem the opposite.

I have noticed a few vertical lines in the cylinder wall looking thru the exhaust port (intake side). Possibly low compression would cause the rich pilot situation.

firsthere wrote:Thanks, very nicely done!

What puzzles me is how a leak would cause a rich condition. It would seem the opposite.

I have noticed a few vertical lines in the cylinder wall looking thru the exhaust port (intake side). Possibly low compression would cause the rich pilot situation.

You're right an air leak would cause it to run lean not rich. I think we started talking more in general that if you're going to tear it down for a look and put it back together, the leak down is good so you know exactly what's right and where there could be a potential problem later down the road. After my top end job I had a pretty bad air leak that I had to chase down. Mine was losing air becasue of the oring on the slotted left side Kips cover. It's the one thing I didn't change and I'm glad I did the leak down for piece of mind.

A right side crank seal leaking will mimic a rich condition. Hence why leak down tests are a good diagnostic tool.

SS109 wrote:A right side crank seal leaking will mimic a rich condition. Hence why leak down tests are a good diagnostic tool.

Hello! I forgot about that part, thank you SS.

Its not using any crankcase oil that I have noticed so kinda ruling that out for now. I got it running better after installing the fmf turbine core silencer, plus changing to 50:1 helped the spooge problem. HP2 seems to have a high flash point compared to Maxima 927 i experimented with (40:1).

There seems to be a 1/4 throttle surge that leads me to think raising the needle from three to four down from the top. Any ideas how much would that affect the pilot mixture off idle?