03 Wr 250- Can this bike be saved?

So last summer I bought my wife a super clean 03 wr 250. Really low hours. This bike has been difficult to say the least. Tried to jet it myself using the great info available on this site. But the dreaded bog will not go away.

Gave up, took it to a good Yamaha dealer, they had it for a week. The bike still had a an off idle bog. They took it back in the shop, and had it for another week, and it slightly better. Between the clutch drag and the off idle bog the bike is really difficult for my wife to ride. You have to barely roll the throttle on or the bike dies.

I have done the oring mod for the bog, it still bogs. The clutch drag is crazy, it is almost impossible to find neutral with the bike running. ( I added the washers to the clutch springs, that helped for about an hour. Now it is worse than it was.

I don't get it. The bike is becoming a paper weight in the garage. My goal was to get it plated and do some more trail rides this summer but I am getting close to raising the white flag. My wife has lost all interest in riding it. Not sure if I should cut my losses or keep spending my very limited free time and money try to get this thing rideable.

We have had 5 other yamaha mx bikes, and they have been really great. Not sure what the deal is with this bike. It seems Yamaha should have recalled this bike and made the corrections.

It can be saved!!! It is a great bike if unleashed. What have you done to it? All the free mods? Aftermarket exhaust? Do this, unplug the TPS and remove the exhaust baffle completely. I had a really bad bog at above 1/4 throttle and I bought a JD jet kit and it was almost perfect except the slightest bog at about 1/4-1/2 throttle. I took the GYTR baffle out of the exhaust and it ran perfect!! It ran great but was way too loud. I bought a FMF system and I couldn't ask for a better bike. I feel your frustration because I was fighting the bog and bad but I finally got rid of it. Now you said the bog happens right off idle, does the bog happen when you accelerate from any other part of the throttle like if you are at 1/4 throttle and twist the throttle does it bog? Does it bog holding the idle steady just past idle?

Your clutch drag has been talked about a lot and I believe the big fix is replacing the clutch springs with either YZ springs (I think) or aftermarket springs but most people just install a whole new clutch kit. I, myself, don't really mind the drag so I will take care of it when my clutch needs to be replaced.

There is hope my man, I believe in you!!

Swede thanks for the input, I was looking for a success story . The bog is just off idle, if you are moving it is not to bad. But from a standing start, you have to be baby the throttle to get it revving and then let the clutch out. Not good for the wife, she just stalls it, over and over and over and over and over..... Each time she has to find neutral so the bike will start. Her previous bike was a yz125, so she knows how to use a clutch. I bought the wr thinking it would be easier for her to ride.

The bike runs really good above 1/2 throttle.

It also has the Gytr insert, i pulled that out and it did not make a difference. The dealer supposedly swapped out the leak jet when they were trying to jet it. (Not sure about that, It went from not being started to completed in about 30 minutes)

The tech told me that is as good as it gets, I find it hard to believe that a bike will stall out that easy.

i will try disconnecting the tps. I have also done the Oring mod for the AP.

i bought the bike from my cousin, and he did an airbox mod of some kind. Not sure what else. It still has the original grips, and the original back tire was just replaced.

I will look into the JD kit. I dont want to invest into getting this thing street legal unless it is running right.

Hopefully I will get this thing figured out.

If it is bogging right off idle when you give it gas slowly (not a fast twist) then it is the pilot circuit. If it is happening from a fast twist, then it is probably the AP.

From the sound of it, it is the pilot circuit. I got my bike (YZ250F) setup with a new exhaust and it had a studder/bog off idle. It also backfired like crazy on decell. Turns out I was way lean. I richened the idle mixture by turning the fuel screw out and that fixed it. I ended up at 3-1/2 turns out so I opted for a larger pilot jet and now I'm running a 48 at 2 to 2-1/2 turns out. Make sure you don't make it too rich or it won't hot start. Once I got mine dialed in, it hot starts one kick (with HS lever). Try giving the Fuel screw a half turn out, does that help at all?

What size pilot are you using? If the air box got opened up, chances are you need to go bigger. Les restricted flow, less suction. Less suction, less fuel flow. Less fuel, leaner mixture. Solution? Larger pilot jet.

My brother just fixed the same problem on his 06 WR, installed a JD kit, and the o ring mod, but the bog was still there, then he found that the AP wasn't squirting, the nozzle that squirts into the carb was blocked, he pushed a very thin wire into it, then blew air through, and the bog was gone.

My 04 had the JD jet kit and stock muffler with baffle removed, and it bogged. Replaced the muffler with aftermarket and that fixed it.

Thanks for the advice.

762spr- There is no twisting the throttle fast, you need to roll is back slowly and feather to keep is running until is smooths out.

I will try to work on tomorrow, set what happens.


If you do get a JD kit then all of the free mods need to be done. The JD kit is designed for the bike with an open air box and aftermarket exhaust. Highly recommend the YZ cam timing and grey wire too

Thanks for the advice.

762spr- There is no twisting the throttle fast, you need to roll is back slowly and feather to keep is running until is smooths out.

I will try to work on tomorrow, set what happens.


Yeah, that's what I thought. Sounds like an extreme case of what my bike was doing. a JD kit doesn't replace the pilot, so keep that in mind. I would also get an extended fuel screw... I can't figure out why they don't come with these stock!

With it that bad, I'd say go ahead and get a larger pilot jet. Normally the process is to back it out untill it runs well and go up if it is more than three turns out, but the screw will probably be falling out. Pull the pilot and see what size it is, it will be stamped on the side. It will probably be something like 40 or 43. I think Swede said in another thread that 40 is stock for the WR. I'd wager you'll need a 45 or 48 depending on what you've done to it. A WR owner might have better insight on this. I'm running a 48 in my YZ.

They're like $5 at the dealer and come in sizes like 40, 43, 45, 48 I think you might be able to get exact sizes, but that's all my dealer had. I want to say at least 43 probably 45, but that's just a guesstimate. I'm sure some WR owners will chime in.

Edited by 762SPR

I have a 42 pilot in mine and in the cold winter I bump it up to a 45 and play with the clip position. The key to fixing the bog is to know exactly when it happens. Could either be needle/jetting or AP not working properly

Finally some progress! Messed around with the fuel screw and idle, decided to swap pilot jet (45) to a (50). Huge difference, bike started right up, adjusted fuel screw and the bike is much better. Dealer was out of the 48pj, so I will try one of those when they are back in stock. I will ride tomorrow and see how it goes.

Also, changed the oil and the clutch drag was improved as well. It is now possible to put the bike in neutral when it is running!:smirk:

Thanks for the help!

Good to hear!

Have you tried hot starting it? When the bike is hot, it likes a slightly leaner mixture. The hot start lever is like an anti-choke, it leans out the mixture. If the bike is a little on the rich side, it will probably be a little hard to start when hot. I've got mine to where it starts cold in one kick with the choke on, and hot in one kick with the HS lever pulled. Couldn't be happier!

my clutch has been dragging for a while and I just changed the push lever all the push rods and bearing inside the engine

Problem solved.

Those are wear and tear items that need to be replaced.

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