1/8 sputtering? i am crying for help


Here is my story. I 've bought a wr250 2001 3 months ago and i had a unknown problem on it. One exhaust valve kept slacking. Tried hard to find the problem and i could'nt put 1000$ for a rebuilt just for that. Sold it and put just a little more money to get that beautiful almost new Wr450 2003.

And here another hard to resolve problem with another WR.....

First ride was yesterday. Bike is running well but 1/8 steady throttle sputter like crazy and seem to cut and go ( when i pull the choke the bike when to die when running). Easy, i tought, it's only the jetting. Thing i've noticed was little backfire on decel too. Soo rich and lean at the same time, crazy. I decided to put in 50 pilot (48 stock) didn't do anything. Ha ha i said too myself, misunderstood lean and rich symp. Then i've put 42 pilot...didn't do anything either. I've put back the 48 pilot as everyone run with, but try to lower the needle. (on the 3nd notch instead of 4, on the stock needle) Didn't do anything.

Then after hour of tried to get that search fonction working in TT forum. Some people disconnect the TPS. i dont like the idea but i've done it of course. That helped the 1/8 sputter but not that much, and backfire was stronger.

Then, the carb must be dirty came out. Soo i decided to take off the carb and started with the slider section... it was dirty! little black kind of old sticky dirt. Cleaned it and used some pressure air on every jet, i didn't forget the pilot one! Didn't do anything. Even at idle the motor seems to sputter a little , like if the choke wasn't fully seated. i've checked the choke assembly and nothing special came out. It seems to block the hole correctly. Checked the mixture screw too, it still there in the hole at 1-1/2 turns out.

I have an FmF ti-4 pipe, stock air box, lid on (for the battery) and everything around that is stock. Temp is around 75, 0 altitude, not much of humidity.

Maybe WR and i just dont belong together! i ride at 1/8 steady lot's of time, in those slow technical trail, so i need an 1/8 throttle!!

I've looked for an leak somewhere, but i've double checked all the connections...there is no leak. And i even sealed a section in the air box where dirt could get in.

I am gonna put back the stock exhaust to see if it can be better.

I really need help again. Never been that lost with those new 4 strokes.

Re-connect TPS and don't touch it!

If jetting does nothing, that is a sure sign of an exhaust leak. Take header off bike, line it up properly first by hand, then tighten bolt and nut up evenly, 1/2 a turn on each at a time.

I think those FMF pipes say they need some high temp silicone on the slip fit, where the header joins the mid pipe.

Does she spit out flames??? My guess is yes!

IT's getting 22h00 i'll check that, haven't notice any flames, but i never look behind and friends never told me.

I was only replacing the exhaust, but i'll take off and put back the header as your recommendation.

That's the best thing about this place, many people been there and done that!!!!

Good luck with it!

It looks like i have some leaks on the first exhaust joint. The section on the exhaust which is behind the right number plate. I can see carbon all around it and on the ventilation cut on the side panel. IT might be my problem... i'll continu and check if there is silicon between mid and header and check the fit between cylinder and header. Hope this is it....

It sounds like your needle is too rich. I had this problem before, makes it very hard to ride in slippery conditions and tight rocky tracks. It's like your on and off the throttle all the time. I fixed it by going leaner on the needle. The 48 pilot should be spot on for your temperature and altitude. Possibly when you lean off the needle, you will need to richen up the fuel screw which may fix the backfiring on decel and rough idle. If one groove leaner didn't work, try two. Other things to check are the rubber o-ring and washer is correctly installed on your fuel screw, and hot start operating correctly. Good luck.

All good advice above. Fix those exhaust leaks first.


One other thing to check is the type of needle. Is it the stocker? Does the carb have a JD kit.?The BLUE JD needle willl be too rich. Red #4 in summer is about as rich as you need. After all leaks plugged and if problem persists.

I am not sure if the 04 has an ACV? anyone? If so, that stuck open could cause rich running off idle.


As you are new to the bike :

FIRST set the MJ - check bike runs well at WOT; MJ 165/168 is all you will need in over 80f.

NEXT set PJ for clean idle -adjust fuel screw for less than 1/8th throttle., 48 should be OK as stated earlier.

THEN set needle clip.

As dodjy said, raising the clip will probably require another 1/4 to 1/2 extra OUT on the fuel screw to tame the decel pop.


It might also be worth checking valves if the bike has a few miles on it. It may have never been checked or adjusted. If the bike starts easily it should be OK, but it is easy to check - 20 min job. (much more to adjust!)


It looks like i have some leaks on the first exhaust joint. The section on the exhaust which is behind the right number plate. I can see carbon all around it and on the ventilation cut on the side panel. IT might be my problem... i'll continu and check if there is silicon between mid and header and check the fit between cylinder and header. Hope this is it....

It will be. :excuseme:

After you fix, changing jetting will actually do something again! :bonk:

There was no silicon between mid and header and carbon was close to come out the mid pipe joint, when i've taken apart the subframe, i've certainly moved the mid pipe and then after notice a sputter 1/8...maybe it was there but i would have notice first when i tried the bike before buying it. Can't remember but wasn't that bad for sure.

Everything is back together and sealed with hi-temp silicon. It's 4:00am i cannot try it...damn Ti-4 is loud. i've ordered a Quiet core for it.

Valves never been adjusted, but i've been surprise how easy it start...first kick all the time. Electric start works good too. I'll check the valves today, easy job since i've been there lot's of time on the WR250f.

The JD kit is kind of expensive for me. i have to pay 20$US shipping + 70$ for the kit. 90$ US + custom+ taxes. If that make a real difference over the stock needle i might buy it.

On the sticky, people with stock needle seems to get the best result on the 4th groove. I'll keep it on the 3th for now.

Can't wait to see if the problem is gone.

My jetting is:

stock needle 3nd

Mj 165

Pj 48

Fuel screw: 1 1/2

Others: stock

It's not an exhaust leak! Didn't do anything, i have the same puff puff sputter 1/8 steady throttle problem. I can hear there something wrong even if i dont ride the bike. In the garage, idle and 1/8 do sputter things.

1-I'll checked the gas screw and o-ring, i doubt something missing.

2-I'll do a search for the ACV. and check if it's stuck open.

3-Then, if nothing fix it, i'll try put back the stock pipe.

4-Then maybe going to the 2rd groove on the stock needle? But that didn't improve anything when i've switched 4th to 3.

OBDUQ is the stock needle. i've just put it on the 2nd groove

Pilot screw has o-ring and washer= good

ACV is right, rubber seal is good and not collapsed spring is fine and i've put back the assembly correctly.

Test in 20 minutes.

Didn't do anything! God i start to be tired.

Sputter idle and 1/8. Should i try 5th position instead of going down to 2nd??

here again, i am with a new WR that i cannot use. I am working so hard on that one i might lost my interest. i am thinking selling it now for sure, i am just upset... each time i have a problem, nothing seems to fix it. I have done pretty much all i can do.

Do you think it might be only the plug?

I have looked at the valves, they are perfect even if its never been adjusted. Plug electrode look not bad but the outside was rusted like hell. never seen a plug that rusted! Must be the stock plug as well.

So now i am waiting for my new plug i'll take special care for the plug cap: Ref Yamaster.

I have plugged the exhaust to see what happen reduce the hole from 2 to 1 inch and dont seems to do anything.

I've adjusted the play for the hot start, there is enough.

What else it can be?

Pretty sure needle doesn't affect the idle and almost 1/8 throttle. Should i try 5th groove?

Rusted plug could be the cause of the whole thing. Spark may not be strong enough to ignite a lean mixture because of arching through the rust. When you get your new plug, make sure you plug the small drain hole on the right side of the motor when you wash your bike.

No it's not the plug: sputter again!

Any idea guys before given up? it's been 5 days i am working on it!!

You might want to bench test your electronics...

You probably have a jetting problem. It is probably your leak jet or something like that. Do a search on leak jets. The Boysen Quickshot helps with that too.

No it's not the plug: sputter again!

Any idea guys before given up? it's been 5 days i am working on it!!

I'm with Matty05, I would say you have an exhaust leak. If you are certain you don't, you might have to clean out your keihin again. Probably gummed up port in it some where.

I've been road testing it with the stock pipe today. I've put back the needle clip on the 3rd groove, turn out 2 1/2 pilot screw. Guess what same problem. When i give some gas and decel there is sometime a huge backfire! even with the 48 pilot.

I've taken off again the carb to see if the slide plate was correct. It is placed correctly with the cut down.

I am going to check again for leaks, specialy the header cylinder section.

(as Dodjy said)

Do you really think the needle can be that far off? i have an OBDUQ.

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