KDX 220 low end sputter

[NCFRC]

I have a 35mm carb on my 220 and overall it runs pretty decent but I've been chasing a low end , 0 to 1/4 throttle sputter.

Any suggestions ? I 've changed the pilot jet and needle all over the place.

I'm thinking it's too rich ,, but honestly hard to tell.

 

[julien_d]

What sort of sputter are we talking about here? All 2t's will sputter when cruising at low throttle openings. They don't cruise the way a 4t will.

If it stumbles more than it should, it could be rich. Doing a plug reading with a fresh plug after riding it solely in the "sputter zone" should tell you if it's lean/rich.

 

[NCFRC]

I'll try it with a fresh plug.

I'm only comparing it to my son's 200 which has almost no
sputter at low end.

It doesn't run bad or lack on power , just sounds like it's missing.

 

[julien_d]

Any suggestions ? I 've changed the pilot jet and needle all over the place.

What changes have you made? Any difference at all between the changes?

 

[carlby114]

I have a 35mm carb on my 220 and overall it runs pretty decent but I've been chasing a low end , 0 to 1/4 throttle sputter.

Any suggestions ? I 've changed the pilot jet and needle all over the place.

I'm thinking it's too rich ,, but honestly hard to tell.

Im having the same problem with the stock 33 mm carb and I cant get rid of it either . I was going to try a 35 mm carb off a 200 . I cant seem to get any answers either .

 

[carlby114]

kdx sputtering

Im having the same problem with the 33 mm carb . I wanted to try a 35 mm off a 200 . I was hoping that would solve the problem . I cant seem to get any answers.

 

[NCFRC]

Well I believe I've found the running difference between our 200 and 220 .

My son's 200 has 10.5 compression and my 220 has 8.3 compression
I was running the same fuel and Fuel / oil mixture in both bikes.

The 200 with more compression can burn the mixture just fine but
the 220 with lower compression can't at lower rpms.

What I did last night was to mix a new batch of fuel with a higher oil ratio 40:1 " I was running 28:1 " and the bike runs much better.

Sputter's not 100% gone but a great improvement.

I moved the jetting and air screw all around with no change like it
made by changing my fuel.

This winter I'll put in a new Wiseco and the head machined to get the compression where it should be.

I should have known as I ran across a similar situation years ago , many years ago and had forgotten about this.

Let me know what you find with your bike . The 35 mm is worth the performance gain but don't change it to get rid of the sputter.

 

[jonooffler]

Hi this sound just like my bike (2003 KDX 220 stock- I think ), I bought it about 5 weeks ago, at the time I could not ride but the bike started and reved fine all sounded good.
I have just taken it out for the first ride and i feels alful, from cold the engine felt like it was about to die if you opened the throttle it would die It felt like it was running on full choke.As the bike warmed up it got better with the high revs pulling well but low down it is very lumpy and bogged down. The plug is and 8 the gap is fine and its dry but a dark ish brown.
I have not tried pulling the carb out to clean it but I'm thinking that maybe the pilot jet may be blocked. The last owner didn't own the bike long and did not know if the last owner a changed the pipe and jets.
So any help that you can give would be great.
Jono

 

[GreatBritishRob]

Hi this sound just like my bike (2003 KDX 220 stock- I think ), I bought it about 5 weeks ago, at the time I could not ride but the bike started and reved fine all sounded good.
I have just taken it out for the first ride and i feels alful, from cold the engine felt like it was about to die if you opened the throttle it would die It felt like it was running on full choke.As the bike warmed up it got better with the high revs pulling well but low down it is very lumpy and bogged down. The plug is and 8 the gap is fine and its dry but a dark ish brown.
I have not tried pulling the carb out to clean it but I'm thinking that maybe the pilot jet may be blocked. The last owner didn't own the bike long and did not know if the last owner a changed the pipe and jets.
So any help that you can give would be great.
Jono

Try reading your other post. :cool:

 

[NCFRC]

The other thing That I believe may contributing to this is Ethanol in gasoline " pump fuel " . Not a good thing when you fill your 5 gallon
can that there's 1/2 gallon of Alcohol in the mix. :whoa:

I just learned that the marina's have non-ethanol fuel because of so many running problems ,, the only slight negative there is it's only available in 87 octane.

 

[jth]

NCFRC
I had the same problem after I went to a full RB modded engine.
¼ throttle bog (like a lean bog) + pilot and air screw adg. made no change.
Problem solved by going to the next larger main jet.
When you changed to the 40:1 fuel you effectively richened it up pretty good
With your results suggesting that you are experiencing a lean bog.
Try a bigger main jet with the 40:1 fuel and let us know how it works.

 

[NCFRC]

I don't believe it's a lean bog , I'm quite sure it's a rich stutter like the fuel isn't burning completely.

 

[jonooffler]

I have just changed the pilot jet over the other night but have yet to ride it ,it was running a 42, my local bike shop had a 38 so I have dropped that in I hope to ride it over the next few days to see how it goes. I did just kick it over and it does feel much better.

 

[jonooffler]

Aaaaaaaah

Well i tried the new 38 pilot today it feels a bit better, it still pulls well at high revs in the higher gears but low gears still has the stutter.
I rode for about 9 miles then pulled over to adjust the air screw.The idle was fast and the breathers were all leaking fuel. I killed the engine and restarted it fine, then I tried to adjust the air screw, when it is in the motor dies as you open it out it picks up but does not change if you go out more.HELP
Any ides before I trade it in for a 4 stroke.
Jono

 

[NCFRC]

38 is way too lean for a low speed pilot jet.

Is this a 33 or 35 mm carb ?

Send your carb and cylinder head to Ron Black

 

[jonooffler]

Hi it's a 33 carb, I would love to get the RB work done on the head but that might have to wait until the wife starts talking to me after I brought the KDX home ;) .I have decided to change back to a 42 and then flush the tank out a start with a new mix of fuel i mixed the last lot 32-1 so I going for a higher octain and a 40-1 mix to see how that runs.
I have only just started riding the KDX off road but must say after 2x DR125 1xDT125R 1xDRZ400 1x XR250R and a TE610E this one is the best. I ride slowish green lanes and if I can get her running right at low revs this is going to be a great bike.

 

[NCFRC]

It's a lack of complete burn of fuel at low rpm's.

Were you running 87 with this problem ?

You'll also see it with premium oils and a high flashpoint , more so if it's mixed too rich ,,,, 40:1 should make a noticeable difference.

 

[james.keaton]

I have always ran 93 octane and bel-ray 2 stroke oil in mine, as did my nrother in law who had the bike 15 years before selling it to me.

 

[jonooffler]

Hi I was running 95 with a 32-1 I flushed out the old petrol and change the jets back them ran out of time so this weekend will show if its worked.
Thanks again for all your input

 

[carlby114]

Im having the same problem with the stock 33 mm carb and I cant get rid of it either . I was going to try a 35 mm carb off a 200 . I cant seem to get any answers either .[ change the needle . just put in a a CEK cleaned it up just off idle . the stock needle is a B the C is actually a smaller dia. but the taper comes in later, getting rid of the sputtering , 38 pilot 145 m 2nd groove 1 3/4 a s go on line to pats small engine plus (there only $5.50)

 

[jonooffler]

Hi mate sound like we have have the same issue, every one keeps telling in on forum that the 38 is too small, I have yet to look at the main and clip on mine but if yours is set as you say thats the stock setting.
Have you changed the clip on yours ? the local bike shop told me to drop it down a notch to run it lean to see what that would do. I have sort of run out of time with mine at the moment so it will be a few days before I can check mine out to se what it is set to.I have been give a few other things to look at but have not tried them yet, they are ;
The KIP valve.
Reeds
I don't know if you have tried any of these out .Please keep me posted I would love to know how you get on.
Jono

 

[NCFRC]

Well I have to admitt when I'm wrong as we rode this last weekend and it stuttered as bad as ever. I even went from a 42 pilot up to a 45 and the stutter is the same. The 45 did seem to help low end torque above the stutter.
I'm really leaning towards pulling back out the reed cage and double checking the 607 reeds I installed . They were nice and flat when put in this spring but you never know. Another rider commented about trying the V-force 3 cage but thats an expensive try.

We're running Maxima 927 at 40:1 and they still smoke alot.
I may try a higher mixing ratio for the smoking but I don't think it will help with the stutter.

Again this seems to be a 220 characteristic as my son's 200 runs perfectly smooth at any rpm setting.

This 220 has far more pull / torque but maybe the screwed up porting causes this problem ?

Somebody must have found the cure :cool:

 

[jonooffler]

Hi I rode into work today on the 38 jet I did feels bit better with the stutter ( but not much ) The down side was a lack of pick up, I played around with the air screw with out much change. The guy I bought the bike from said that he ran 50-1, some people say is to low an oil mix. The lower you go the more rich it will run so I'm not sure that it will help.
Having looked on a few forums I found one thread about the air box lid and snorkel, on guy claimed that he could never get his 220 to run well until he removed the snorkel but leaving the lid in place, after that it was fine.
I have just removed the item and will go out later and try it out, if it works I might go back to the 42 pilot and see how that feels.
Good luck Jono

 

[jonooffler]

Ok tried that and it felt worse, very unhappy at low revs and not great at high revs. Ran round to my local MX bike shop and let the owner have a ride on it and he came back saying that it felt rich and lean at he same time ! He suggested going lifting the needle one notch and see what that does So he thinks make it run richer.
Will give that a go over the next few days and will post the findings.
Jono

 

[NCFRC]

So you have the snorkel on or off the bike ?
I'm running 40:1 mix ratio now but am going to try 50:1 this coming weekend as for average trail riding they smoke really bad and alot of spooge.

I even talked to Jeff Frederette and he's always run 50:1 but also commented that this low end sputter is fairly common no matter how you jet the bike.

The other comment that makes sense to me is that the sputter gets a little worse the longer you ride at a slower pace. Which is a sign of too much oil thats building up and then after you clean it out it runs better. But I've never fouled a plug .

I won't get into oils but I believe if you buy a very high quality oil
that you can't mix it at too low a ratio. Again Kawasaki says 32:1 only to cover any oil thats available and to have plenty of it.

This will be a long term project for me as I'm going to have the head and cylinder done this coming off season to improve the performance to the next level .

I hope this rambling helps to some degree.

As of today I have a 35mm carb ,45 slow jet , 152 main , needle 3rd clip , pilot air screw 2 out .

I'm confident that 50:1 will clear it up some. Fine for trail riding.

If your racing and run the bike from 1/2 to wide open "all " the time then I'd stick with 40:1 .