Idle and rev on a 200

I have a 95 200 that runs pretty good but not great. It's got a fatty pipe and a RAD valve. When first started, it idles fast, really fast for 2 or 3 minutes. Then it idles down and is fine. Once it gets hot it won't idle...even with the idle screw all the way in. Let off the throttle and it will idle for about 3-10 seconds and die.

I've got a 42 pilot and 148 main jet in. It seems to bog at the top of the mid range/beginning of the high rev range. I've played with the float level...it's back to stock, needle position, took the top end off and put new rings in and cleaned and checked the KIPS. It was stuck, but now it's working. The plug looks like it's still a little fat on the 148. I was wondering how small have others had to go. I guess it's around 800 ft here and really humid most of the time so the air quality is crappy.

I think the pilot is pretty good because it's pretty snappy and clean to about 1/2-2/3 throttle.

This is my first KDX and it's still tons easier to ride in the tight stuff than the 92 KX250 I had. That just about scared me off two-strokes for good. Glad I tried the KDX.

Rhodester said:

You are too lean on the main jet. Try a 152 or a 155. I'd stick my piston with that main jet at your elevation. As a matter of fact, that may be why it won't idle when it gets "hot". I wouldn't consider a 148 unless I was over 6000' on a warm day. I'd look for a vacuum leak or chipped reeds for any additional idle problems (intake boot cracks, head and base gasket seal, etc.). Going up to a 45 on your pilot might be worth a try. You should start with the air screw 1 1/2 out and adjust from there. Make sure that someone didn't over tighten the air screw and ruin it.

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Thanks. I'll give that a shot. I just refreshed the top end and put new reeds in. I just wondering why it wouldn't idle because of too lean a main jet?? I ordered a couple of jets and a new float, needle, and needle valve, since it's leaking out the overflow if you leave the gas on. I'll get the float right and then start on the jetting.

Rhodester, I don't know if I mentioned my bike has a RAD valve on it. Everything I've read about it says that will need to be jetted leaner than a stock reed.

Rhodester said:

My '95 had a RAD Valve on it until just recently....I caught that you have one too.

I was running 152, DEK/3, 42, air screw @ 1 1/4 out, #7 TV, FMF-35 (woods), FMF "Q", air box lid on with snorkel removed, 2600', around 80 degrees, dry climate, RAD Valve, MX2T @ 40:1. This jetting was with the stock carb. Now I'm running an RB Air Striker and a V force 3 reed block.

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How do you like the Air Striker? Did it make a big diff? Did you have to take the RAD valve off for it, or just want to go with the V force?

Mine's got a FMF Burly pipe, not sure what silencer it is..no labels or anything, but I just repacked it. I've got a couple of main and pilot jets on the way, so I can get it dialed in.

Rhodester said:

You are too lean on the main jet. Try a 152 or a 155. I'd stick my piston with that main jet at your elevation. As a matter of fact, that may be why it won't idle when it gets "hot". I wouldn't consider a 148 unless I was over 6000' on a warm day. I'd look for a vacuum leak or chipped reeds for any additional idle problems (intake boot cracks, head and base gasket seal, etc.). Going up to a 45 on your pilot might be worth a try. You should start with the air screw 1 1/2 out and adjust from there. Make sure that someone didn't over tighten the air screw and ruin it.

Click to expand...

I put a 45 pilot and 155 main in it now and no improvement. I have a 40 pilot and am going to try that. It seems to be really sluggish on the bottom and won't idle once the bike warms up. I even got a new air screw and idle screw thinking they could possibly be damaged.

I am scratching my head.

markmad said:

wonder if you don't have a needle and seat issue with your carb as you did say you have fuel running out if you leave the tap on?

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I put a new needle in it, and I can't see a part number for the seat and it doesn't look like it comes out. My fuel shutoff was leaking so I fixed it. It was only leaking out after sitting for an hour or two, so I don't think that's the problem. I've gone from a 148 to 155 main with no difference. I have a 45 pilot in it and will go to a 40 so see if there is any difference. I just noticed fuel in the flywheel housing. Jeff Fredette says there are 3 slots around the crank seal/bearing that can leak over time. So as soon as I get a flywheel puller, I am going to yank it off and JB Weld them and see.

Has anyone had this happen and what differences does it make? The bottom end was supposedly redone last fall and I hope the crank seal is not leaking.