95 WR250z Carb Setup Help

First off, I have conflicting info on the choke. The manual explains the knob that is found on the YZ motor but not the lever that is found on my WR. The manual says pull the knob up to turn on the choke, down to turn it off. On the WR, the lever up would be like the knob being down, and then obviously down would be like having the knob up. Which is on/off for the choke on the WR lever? I have been riding with it like this: lever down for choke on, lever up for choke off.


The bike fired up today, but I think it may have fouled a plug. I installed my new pilot screw, adjusted it to 1 1/2 turns out, kicked it a ton of times and got it to fire up. It ran well and when I flipped the lever up (what I thought is choke off) at idle it would start to die, flipping the lever down would raise the idle back up. Rode down the street, and it was running fat in the mid range, got a good rip though the top and it cleaned up and ran well. All the sudden it bogged and died. The plug was soaking wet with gas. I can clean the plug real good and get about 3 sec of running super rich, but then it dies and will not restart. Seems to start easiest with the pilot screw at about 4-5 turns out. (again still not sure if im running with the choke on or not)


The last thing is I am looking for jetting recommendations for 3-6000'. Right now it is set with a 360 main, 40 pilot, clip in position 4 on the needle and to get it to run clean before the plug fouled, I had like 5 turns out on the pilot screw. I thought after reading the manual that I ahd been running with the choke on, but the bike ran decent, although did have a pretty good amount of splooge out of the exhaust.


After I got it about a month ago, I got it running well by leaning the pilot jet screw. I ran it like that for almost 200mi riding mostly 2-6000'. I rode a lower elevation area on laybor day and had a hell of a time starting the bike, but once it was fired up it ran decently. After I got home I found that my pilot screw had wiggled out (likely because of how far out it was) and the bike was too lean to start cold due to no screw in the hole.

My '97 was pretty difficult to get tuned. The mikuni just isn't as easy as the yz's carb. The choke isn't a choke at all, it adds extra fuel through the pilot circuit making it an enrichment circuit. It is off when it is up, and on when its down. If it runs better down, I'd say take the air screw in to see if it helps. You might end up needed a larger pilot jet. Your main seems a bit small to me, but I'm at 600ft elevation. My setup below


40 pilot

air screw 2 turns out

second from the top on the needle

380 main jet

Ok that is good at least, that is how I have been operating the choke. I think the pilot is too big, I had to run like 5 turns out on the air screw to clean up the bottom end. It always rips up top so the jetting seems to be at least close on the top. The jetting seemed to be on the rich side but I'm also riding pretty high elevations on tight single track climbing hills the whole time. Also the yamalube seems to splooge a lot more than the valvoline I was running.

I did raise the needle height 1 clip back to the stock setting as it was on clips position 3. Hoping that will clean the mid range up a little so I can adjust the pilot screw in a little.

You might have a leaking right side main seal causing you to burn transmission/engine oil. My WR had that issue, causing it to run rich no matter what you do to the carb. Measure how much oil you put in ride it a few hours then drain the oil and see if its the same amount you put in, if significantly less, your burning oil through a leaking main seal. Those old WR's are great bikes.

Got a new plug in her today and it fired right up on the 4th kick. Moving the needle clip up 1 made a big difference and the bike now runs very clean with 2.5 turns out on the pilot screw. I think I may have had a crappy plug all along that was fooling my carb tuning.


What would make the idle raise when turning the choke on? It will rise and idle, but then you can hear it start to bog down and want to die. I would think flipping the choke on after its been running a few minutes would bog the idle...


Ill have to check into the main seal next to be sure that isnt causing excessive oil out of the exhaust. Will also need to repack the silencer since it is likely soaked in oil from the last 200mi of riding

Hi, I have a Wr250, 1994 and I have got exactly the same issue, I bought the bike as a non runner ( blown engine) so don't know the history of the bike, have rebuilt it and it will run for a little while before fouling the plug, looks like it's running really rich on the stock carb settings, Did you get is fully sorted 'RalleyTuned' With your carb adjustments ? Or was it the crank seal that was causing the issue?

I have what sounds like main bearing issues so the engine is coming out for a full teardown.

After replacing the pilot screw that fell out, I set the carb back to stock and the spooge has been a lot less. One ride was so bad it was dripping all over the rear tire, now there is no sign of massive spooge out of the exhaust joint or tail pipe.

My main is smaller than stock, needle on the 2nd from the top, stock pilot with air screw at 2 turns out. started mixing 40:1 and that has all help fairly dramatically

What elevation are you riding at? I'm at 2000' at my house and ride up from there so the leaner settings work well.

I'm at pretty much sea level, or just above, I'm running 370 main jet, 40 pilot and I've just moved the needle to the top clip position to try and lean the mixture a bit, oh and air screw is about 2 turns out. Hoping it will run without fouling but have yet to try it on a decent run. New crank seals fitted on rebuild so I'm hoping it's not that!!

All of you that own these 1994-97 wr250's, do youself a favor

and replace the oem spark plug cap. NGK sells one for $4.

There is a resister inside the oem cap that goes bad.

For all you real cheap guys/gals you can take apart the oem

cap and replace the resister with a piece of copper/brass

welding rod. Mine would run rich and foul plugs b4 I did this.

It still has the oem mikuni carb and runs well (complete top

to bottom rebuild)

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