idle problem/jetting question 03 EC250

[bryanaverill]

Any recommendations on improving idle stability? My idle gradually slows and the engine dies unless I adjust the idle speed quite high. I have played with several pilot jets from 35 to 42. The 42 seems to give me the best throttle response and low speed lugging power that I need for tight single track woods riding. The leaner jets cause a bog in throttle response. I have adjusted the idle jetting and air screw according to the traditional method of maximizing idle speed.

Current jetting
main: 175
pilot:42
air screw: 1-1/2
needle: CCK (1)
slide: #7

Plug: stock NGK8 (not sure rest of code)

Pipe: FMF Gnarly

[GMP]

No altitude/temp specs given. CCK (1) is lean for 0 - 1000' Couild you be trying to compensate for a rich straight dia with a low needle position? I always had good luck with D needles on the 250s, Cs being lean sometimes. If it were mine I'd verify the carb is in good shape and nozzle not worn out, then try a D needle with a larger straight dia. (DDL, DEL) and see what that does. For C series a CEL has the same dia.

[bryanaverill]

Altitude 500 - 3500' (mostly 1000'). Fuel 50:1.

I've tried N1EF (stock) and N3EW needles. With various pilot and main jets and clip position. They were all worse in different ways. I may have missed the magic combo but my current jetting is very good other than the idle issue.

What part of the tuning is responsible for throttle response and/or a bog? It seems most sensitive to the pilot jet and air screw.

[GMP]

I'm on my third 250. They all ran well with a DDK/DEK and #7 slide, but the JD Blue is the bomb. I'm @ 1000' as well. '03 is getting old so perhaps your nozzle is worn. Needles are cheap, try a leaner straight section, if it idles the problem will be narrowed down.

[Jakobi]

Originally Posted by bryanaverill

Altitude 500 - 3500' (mostly 1000'). Fuel 50:1.

I've tried N1EF (stock) and N3EW needles. With various pilot and main jets and clip position. They were all worse in different ways. I may have missed the magic combo but my current jetting is very good other than the idle issue.

What part of the tuning is responsible for throttle response and/or a bog? It seems most sensitive to the pilot jet and air screw.

Like GMP said. If your bike is truly happy everywhere but idle and you're not compensating for a rich idle by lifting the clip and winding the idle in, then use the name needle with a thicker straight diameter.

If moving the needle clip has any impact at all on the idle, then you have not set up your idle circuit properly.

Go a leaner diameter. Start middle clip. Back idle speed screw right out. Then in just enough to lift the slide. Try pilot jets with air screw fixed at 1.5 until you find the one that idles best. Then tune your needle clip position, then your main.

A change in diameter may require a change in pilot to maintain the idle mix. You can fine tune the AS either side of the 1.5 turns once you have the bike idling.

[bryanaverill]

My idle adjust screw (thottle stop) is almost all the way in and the idle is high. This obviously means my main circuit is providing fuel.

I'll back off the idle adjust screw until I get a medium-low idle (which it won't sustain because I've already tried). This should take the main circuit out of the equation, right? Then I can diagnose my pilot circuit by pulling the choke. If the engine speeds up then the pilot jet is lean. If the engine speed slows then the pilot is close to correct. If it dies suddenly then the pilot is too rich. All correct?

If I have success with this procedure, how do you fix a bog without adjusting the pilot jet? Needle diameter, taper, clip? Thia is my main question?

[stainlesscycle]

needle diameter will probably fix it. you will need to change pilot to compensate for the wider needle. don't know if you can modulate the choke enough manuallly to be able to see the changes

back your idle screw out to 2.5 turns out. get a leaner needle diameter, start with a larger pilot. maybe 48ish. go 1.5 out. start turning air screw out 1/2 turn at a time with 5 second pause between it until engine speeds up. if it doesn't speed up by 3 turns out you need to go leaner on the pilot.. and repeat air screw adjustment. you may need to blip the throttle in betwee air screw adjustments to get motor to settle down.

[gasser]

Originally Posted by GMP

. If it were mine I'd verify the carb is in good shape and nozzle not worn out.

How do you check it Glenn? I can't tell by just holding it up to the light and looking through.

[bryanaverill]

OK, I read the other idle thread. From what I can tell the secret seems to be a lean needle straight diameter and a rich PJ (compared to stock). This is what you have been telling me all along.

I have an N3EW which has a 2.735 straight diameter. This is A LOT LEANER than the CCK that I'm currently running which has a 2.695 straight diameter.

I also have the problem with a hanging idle as descibed in the other thread. I guess this make sense. The engine is basically running at a high idle on the main circuit. Then the idle speed drops and the pilot circuit is too lean and the bike dies.

So I'll try the N3EW needle and a #45 PJ. I don't have a #48.

[stainlesscycle]

i plugged n3ew vs. cck into jetting chart.

cck(1)/42/175

is almost the same as
n3ew(2)/45/175

but there's a big rich spot 1/8-1/4 throttle. so that should get you close. you may not even need to go to 45 pilot - depends on how close to the edge your jetting is.....