03 wr250f problem's

Im having a problem with off idle bog and will only run with the choke on.. any suggestions?

Buy a new pilot jet. Install it then with a hot engine, set the fuel screw for a perfect idle.


For the bog, check the AP, confirm you have a good squirt.

Ya I just put a new pilot pilot in there and nothing

Take a close look (with good lighting) at the hot start retaining nut that holds the cable and plunger into the carburetor body.

When wrestling with carburetor removal/installation, it can get stripped or broken.

Thats good its holding in there tight.. ima try the .115 ap screw gap with the o ring mod and see if that helps. Its upsetting I bought the bike brand new in 03 it only has 789 miles on it cause I never ride it

If the bike ran well at one time and does not now, it is not an adjustment, it is a clog or part failure. Do not adjust the AP timing. First confirm it squirts. If not, check the diapghram and enure the passage ways are clear. Leave the timing screw ALONE.

It has never ran

First, get the bike pilot and fuel screw right.

Fuel Screw/Pilot Jet
Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.
Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly).  Once warmed, slow the idle to the lowest possible speed.
*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***
Turn the screw in until the idle becomes rough or the bike stalls.
if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.
If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.
Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.
If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.
If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.
If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,850 rpm, but go by the spec in your manual.


Next, make sure the needle is correct. Test at various throttle positions, steady state, under load. Make notes of how it runs - STEADY throttle!!! If you want, you can put tape on the grip and the throttle. Place marks to equate to 1/8th, 1/4, 3/8ths and so on.


Then do the main jet. between 7/8ths and WOT.


Ensure the AP squirts. If it dos not spray like a super soaker, service it.


In the WR450 forum (and in your manual) is the specific method needed to adjust the AP timing. DO NOT WING IT!!!!


Your QS3 is really carb jewelery. Set it to be a #40 leak jet (I think that is 7/8ths of a turn from gently closed).


Do the oring mod.

I figured it out very very weak squirt barely see it

See my first post in this thread.

Ya you nailed it. So now I was told to check the diaphragm and make sure nothing is clogged the bike sat for a long time

Mine got that problem recently.  The fuel screw O ring got trashed and part of it stuck in the orifice.   It took a lazer pointer to see it. 

Bog is gone but will only run on choke

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