low speed stutter

[etuke]

I posted this last night but its not here now so I'm posting again.I have a 2002 kx250 I just bought but you cant seem to just go a slow speed.at about 1/8 throttle it stutters and surges,even if comming down from high rpms it will surge with the throttle closed.This makes it very hard to drive the bike in tighter situations,if you open it up it will scream with no problems.I'm wondering do I need a smaller pilot,adjust the needle or clean the power valve?This is my first 2 stroke and my very first kawi so I'm a complete noob but I know how to work on bikes.

[The Spanky]

What's your current jetting?

Surging when the throttle is closed usually indicates a lean pilot circuit, but stuttering usually indicates a rich condition, perhaps with the needle.

[etuke]

just pulled the carb apart and it has a 55 pilot.The carb boot behind the filter was really dirty.Got that cleaned carb looks clean.The throttle cable is freyed and lil pieces of the wire was into the top of the carb.I'm hoping nothing get through the intake and into the engine.I have'nt checked the needle yet.

[The Spanky]

That frayed throttle cable is scary. That was a stuck wide-open-throttle waiting to happen. Good thing you found it! ?

[etuke]

needle was in the 2nd from top,it also has a 165 main.I changed the pilot to a 48 and put the needle in the middle.It still sputter and surges but its not as bad,would a 45 pilot be ok or too lean?I gotta get a throttle cable for it before I can try anything else.I cut the cable and took off the housing,removed all the freyed parts and put it back in the housing then soldered a knob on it,filed it down and went riding:).couldn't have the bike down for a day.Only thing is I'm riding on a cable that 1/3 as thick as before,don't expect it to last long.

[The Spanky]

A 45 is pretty lean, I run a 50 or 52 depending on weather, but I'm at sea level. What's your altitude?

Is the bike stock, Have you checked the reeds? What's the air screw set at?

[etuke]

sea level here,stock except for the fmf and the pro circuit,bought it this way.I think I'm gona put the 55 back in,the 48 didn't clean it up enough to be the jetting.The plug with the 55 was a tan color so it looked good.when I pull the carb off i'm gona pull the reeds out and check them.What should I look for?Its just that one throttle spot rest of the positions are great,it starts off good but when it starts to get the rpm's close to the powerband it sputters,then when I close the throttle like when coming to a coasting stop it will surge a couple times just before idle.Do all these bikes sputter?

[The Spanky]

Put the 55 pilot in (or a 52 if it's hot and humid) and try dropping the needle to the top groove.

No, it shouldn't stutter.

[etuke]

i checked the air screw and its at 1.5 turns out

[hi_im_sean]

emulsion tube clean?

[etuke]

emulsion tube clean?

now you lost me,where would that be?I put the 55 back in and put the needle in the top position and it seems worse and the throttle resonse is worse.I have to turn the air adjustment out 3-3 1/2 turn to get the sound right,to me its rich.I checked the reeds and they are fine.Is it possible the choke is off adjustment and only affecting low speed throttle?When it sputters it sound like low grade gas(engine ping/knock) but its quiet other wise.I would really like to get rid of this sputter,the surge I can live with.Could it be timing?I would really like to go down on the pilot to get the response back but how far can I go?Riding at sealevel and it very damp here at the moment.

[etuke]

quick question about the reeds,I had them out and there wasn't any cracks and no pieces missing but I did notice 1 of the reeds didn't seal to the base,it was up just a fraction,I took it off and cleaned around it but didn't flip it.Do you think this could be my problem?

[The Spanky]

A gap of a couple thousandths is OK. Any more than that and the reeds should be replaced. I don't flip reeds, because I run carbon fiber reeds. Flipping them is just asking for broken reeds.

I don't think that is your problem. Since you are at sea level, and it's cooler there than it is here (I'm running a 50 pilot currently, sea level at 90+ degrees), I'm starting to think your enrichener could be leaking fuel even when it is closed. The enrichener only adds fuel at closed throttle through about 1/4 throttle, exactly wehere you are having the issue.

By the way, are your reeds stock?

[etuke]

I think they are stock,they are yellow in color looks like fiberglass.When you say enricher where would that be,I haven't heard that before.Thing is it runs excellent when its under load,no stutters what so ever its only when the revs come up to almost powerband,I can keep the throttle in the same position but when it revs up it starts to stutter.Under load it works perfect.High gear in the same throttle position runs good,gear down in the same position and it stutters.Like it reving but not enough fuel to keep it there or a bad mixture.Im still thinking its a jetting problem.Do you think I could run the 48 with no problems,temps here usually only get to the 80's but now its in the 60's-70's.

[The Spanky]

I think they are stock,they are yellow in color looks like fiberglass.When you say enricher where would that be,I haven't heard that before.

The enrichener is what most people call the choke. It's not really a choke, it's just an extra pilot circuit that adds fuel at closed throttle for cold starts

Thing is it runs excellent when its under load,no stutters what so ever its only when the revs come up to almost powerband,I can keep the throttle in the same position but when it revs up it starts to stutter.Under load it works perfect.High gear in the same throttle position runs good,gear down in the same position and it stutters.Like it reving but not enough fuel to keep it there or a bad mixture.Im still thinking its a jetting problem.Do you think I could run the 48 with no problems,temps here usually only get to the 80's but now its in the 60's-70's.

Your problem is perplexing. Your description sounds rich, but the thing is that cooler temps like yours require richer jetting, yet you had a leaner pilot than I run and it still seemed rich. At 65-70 degrees I have to step back up to a 55 pilot or the bike surges when I close the throttle.

[etuke]

mine surges at closed throttle too.I wonder if I should try the needle in the lower positions.the choke seems to work fine,it starts real easy when cold and it revs up until I push it down then it idles good.

[hi_im_sean]

now you lost me,where would that be?I put the 55 back in and put the needle in the top position and it seems worse and the throttle resonse is worse.I have to turn the air adjustment out 3-3 1/2 turn to get the sound right,to me its rich.I checked the reeds and they are fine.Is it possible the choke is off adjustment and only affecting low speed throttle?When it sputters it sound like low grade gas(engine ping/knock) but its quiet other wise.I would really like to get rid of this sputter,the surge I can live with.Could it be timing?I would really like to go down on the pilot to get the response back but how far can I go?Riding at sealevel and it very damp here at the moment.

its the part the main jet screws into. having thought about what you said, this wouldnt be the problem, dont mind me, your in good hands

[etuke]

put the needle in the middle position and flipped the reed,it seems a tiny bit better,the surging is better.For the difference in the jetting it has to another cause,it didn't make enough change to be a jetting problem.Was talking to a small engine mech and he said I probably need the power valve cleaned so it will be going to the shop next week to get done.I hope that fixes it,although I'm starting to get used to it now and its not so bothersome.I found out today that somebody put a 14 tooth on the front,I knew it was a bit difficult to start off,have a 13 tooth on order now.Rear sprocket looks small too,couldn't find the # on it and didn't bother to count the teeth.It will pull the wheel up in 3rd now with no effort so with the 13 its gona be even easier,Can't wait ?

[The Spanky]

The power valve can cause some strange running symptoms if it's sticking, but acting rich isn't typically one of them.

Stock gearing is 13/49. I run 13/51.

[AdvCoop]

The enrichener is what most people call the choke. It's not really a choke...

Oh yeah? Then why does my OEM manual call it a choke? Huh...huh...why? ?