03 WR450 stalling off idle

This post probably should have gone in the jetting forum but because it relates to my last post (z start and stalling problem) I put it in here. In one of the responses from ncmountainman he said the z start could stall the engine if it was running rich. So today I thought I would check it out. Amazing I found I could turn the fuel screw all the way in and almost all the way out and the engine did not stall. In other words I could not make it lean enough to stall! Lightly pulling on the hot start (adding more air) made the engine rev faster so the starting point was that it was far to rich. Also opening the throttle produced an 8 stroke stutter before revving out cleanish.

First job was a full clean out of the carb and blow out all the airways and check out the jet sizes. It was as a standard european model should be. Re-assembled and tried it and it was exactly the same. :banghead:

Changed the pilot jet for a #42. managed then to get a peak tickover about 1.5 turns out on the fuel screw and it stalled out about 1 turn either side of that setting. Off idle stutter still there but nowhere near as bad.

Dropped the needle 1 notch. I had to reset the fuel screw at about 2 turns out and voila! no off idle stutter.

I replaced the #48 pilot to try it but it was far to rich again so went back to #42. #45 would probably be good but I dont have one. Since then I have tried to stall out the clutch and so far using the rear brake on the carpark have not been able to do it. The bike must have been like it from new or since I fitted the exhaust as nothing else has been done that would cause it. Strange that it should be rich not lean given current emmision laws.

Thanks to ncmountainman for raising the doubt. :banghead:

Anyone else had a similar experience?

that problem took about a month to figure out(about drove me nuts,because as i, most people would've thought it was the clutch) alot tend to keep their jetting on the rich side and these rekluse' amplify it; for some technical reason that i know nothing of,just know it does! glad to be of service :banghead:

Too rich a pilot and even a normally clutched bike stalls more! :banghead:

Indy and Mountainman,

Do you guys have any advice for me. I posted this a while back in the Jetting forum, and got a little bit of advice, but I could use some more input.

When I originally posted this, I had a 38 pilot jet, and a was at 4th clip on the needle. James Dean adviced me to go back to a 42 and drop the needle to the 3rd clip. Which I did. Results were still similiar to my orginal post.

I'm starting to think it's the clutch. My gap is good at .35. I have a heavier preload wave spring that Rekluse sent me a while back, and I have the heavier spring on the adjuster. If I turn the idle up, the problem goes away, but then it lurches in gear, if I set it so it doesn't lurch, the bike will stall.

(Original post in the Jetting forum)

Current jetting set-up for my bike.

Model: 2003 WR450

Timing: YZ exhaust cam instead of WR

Main jet: 162

Pilot Jet: 42

Fuel screw (turns out): .5

Needle/Clip position: 3 and YZ needle NCVQ

Leak Jet: 40

AC squirt: instant start (but doesn't hit slide) and short. Less then 1 second.

Airbox mod: Battery and entire top of airbox removed.

Pipe: Stock pipe with GTYR 96 db insert.

Altitude where you ride: 600-800

Temperature where you ride: These settings tested at 40 - 50 F

2 months ago, I installed a YZ cam and a Reckluse auto clutch in my bike and ever since then, I've had the Bog and Stall right off of idle. I might have had the Bog and Stall before I installed the auto clutch but just didn't know it because I was slipping the clutch..

(All trials and observations below was preformed while riding the bike, and making sure the bike was warm.)

Searching the WR forums, everyone is saying that I need to go with a bigger pilot jet. 48 or 50 vs the 45 that I had in the carb. The bigger pilots did not help. The bike would run good when it was cold, (no bog and stall) but would start acting up as soon as it got warm, or hot. It would bog and stall in vertially every tight turn, and was a real PITA to start.

Finally, I gave up on the advice in the WR forum and started going leaner. I started out by bolting on my buddies YZ450 carb which has no Bog or Stall on his bike and beatiful throttle response. His set-up is 165 main, and 42 pilot jet with a unrestricted exhaust. My bike responded favorably to his carb, but it still Bog and Stalled when the bike got warm. Logic dictated that I need to go leaner since my airbox (at the time) and exhaust was more restrictive then his.

I set up the carb on my bike with the settings I have listed above, except for a 40 pilot jet. This was favorable again. Now the bike would only Bog and Stall occasionally, and sometimes it was only a Bog and stumble instead of a stall. I removed my air box side panel too see what would happen, and once again had a favorable response. The Bog and stall is vertially gone, it's mostly just Bog and stumble.

I drop my pilot to a 38. With the pilot screw at 1 turn, the Bog is vertially gone. 1 out of 10 times, I'll have a tiny, tiny stumble when I snap open the throttle.

BUT, this is my problem: The bike still stalls when it's idling. The most common situation is when I accelerate hard, and then come to a stop very quickly. The bike will idle for about 10-12 seconds, and then stall. Or it will stall if I touch the throttle. And it's only when I am stopped and idling. If the bike is moving at a crawling pace, then there is no issues. the best setting I've found to aliviate this problem is with the pilot screw at .5 turns or less.

Do I need to go to a 35 pilot??? This just seems odd because it is way leaner then everybody else settings. I'm I missing something?

i'm thinking it may have something to do with the smaller opening with the wr cage (its about 15% smaller than the yz cage) increasing the airflow rate/and or vacuum ,the faster the air flows/or more vacuum there is the more fuel is pulled thru the jets(especially with the yz cams. try ordering the 03 yz450 cage and cage reciever(the part that attaches to the airbox and hold the intake) it will fit as i did this to my 04 wr,i have a new stock airfilter(yz450) i could send you to save you a few bucks. if your interested i can dig up the part#'s :banghead: this is only possible with the battery and tray removed as the yz stuff will not fit otherwise. actually while your at it the yz airbox is only $50 and its a pound lighter,also the sides are solid so no more side seal issues :lol: the only thing that needs changing if you change the whole airbox is the left side # panel needs to be yz.....or just try the 35pj,if you do i'd go to 4th clip though,and experiment with the mains trying maybe a 165 :banghead: i'm no proffesional but thats all i can offer. afterthought, if you do the cage swap you'll need the airfilter bolt,washer,and wingnut too;as the wr flipper deal will no longer work :busted:


If you ride an auto-clutch in too high of a gear, the clutch plates will be continually slipping, heat up, and expand to reduce the clearance in the basket. The result is a grabby clutch and persistant stalling.

Try keeping the idle slightly higher (just below the engagement point) and shift down when the clutch is not being forced to slip for long periods. The condition most often happens in 2nd and 3rd gears. The other alternative is to add a small amount of extra clutch clearance to raise the engagement point.

Do you have the stock fuel screw? ----Occasionally, aftermarket fuel screws will have an undersized tip and richen the pilot circuit at settings that are normally perfect. The other side effect is that the fuel screw needs to be at about 1/2 turn.

Have you ever had a fuel screw damaged during installation?



I haven't fixed the problem yet. The bikes been sitting in the shed since Oct 20 with the dirt from the last race still on it. :banghead: Just isn't enough time in the day...

I do have an aftermarket fuel screw. (MSR If my memory is good...) I have noticed during some of my trials, that I can turn my fuel screw to 0 turns and the bike will still idle and run if my pilot is a 45 or higher. I'll have to mic it and compare it to the stock too the stock screw and see what pans out. Maybe put the stock screw back in...

Weighing everyone's advice, my next course of action is to widen my install gap on the clutch. (can't really swing spending more money on parts right now. wife would shoot me) I don't know if I have swelled plates or not, but I do know that I currently get pretty instant clutch engagement when I twist the throttle. Even when the bike's cold and with the heavier spring I have on the adjuster. I'm thinking maybe adding .010 or .020 to the install gap might be helpful...I'll do that first, and then start experimenting with the jetting again.

(My apologizes to WR450...didn't mean to take over your post... :banghead: )

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