2003 WR250 F - eng. won't idle down and carb starts to overflow
When the bike really warms up running dirt roads, the engine starts to rev higher and won't idle down on its own - eventually, the carb starts to overflow. After shutting down for a while, the carb overflows when I just turn the petcock on. Carb's been cleaned, needle replaced, rubber diaphram (?) replaced, etc. Still a problem.
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Re: 2003 WR250 F - eng. won't idle down and carb starts...
Have you checked the float level in the float chamber?
I guess you may have to reset the float pin adjustment, its allowing more gas to pass through thn required and thus the overflow!
Not bad too, when you are working on the float assembly take the opportunity to blow out the fuel line from petcock to the carburator via the seat for the float pin,any foreign particals there would stop the float pin to seal up and thus overflow.
Fit in an inline fuel filter , this will help keep out the dirt or whatever.
Hope this helps.
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Urals need to be throughly warmed up before riding, old technology engine. As far as the revving, I'd Check for vacuum leaks at the
Carburator with some carb cleaner while idling, and if that's not it, I'd check the choke.
Black smoke indicates that your mixture is way too rich. Now, you didn't say what carb you're running, stock or aftermarket. But, what it sounds like to me is the needle and seat in the carb is leaking fuel and overfilling the float bowl. When you're running down the road, you'll using enough fuel so that the float bowl does not overfill. When idling, you don't use as much fuel, the bowl overfills, and fuel flows into the carb creating a very rich mixture. Is you overflow hose that connects to the bottom of the float bowl connected, clear and open? If so, turn the petcock on without the engine running. If the overflow is clear and the needle valve is leaking, you should see fuel start to flow out of the overflow hose. This is very important that it do this. If the overflow hose is blocked and you forget to turn your petcock off, you could wind up with a couple of gallons of fuel in your engine. It will leak out of the float bowl, into the carb past the intake valves, past the rings and into the engine. I've also seen it get into the primary drive case as well. I'd put a new needle in the carb and check the float setting according to the book. it's sets with the carb on an angle if the carb is the original Keihin CV.
2 things need to be done first start your bike get a can of wd40 after your bike is warm and running spray around the carb jointsall 4 of them if your engine changes rpms up or down you have a intake leak ether your carb joint gaskets or o-rings need replacing or your carb joints are old and need replacing. at this point wont hurt to have you carbs cleaned also
You need to fix the fueling first - without fuel it won't run!
Your other problem sounds like an air leak - either the manifold or the carb. Check by spraying WD-40 or CRC at the manifold and carb join while the bike is running - if the revs change (either up or down) you have a leak.
the float pin is stuck or has some dirt in it. try tapping the side of the float bowl(s) with the handle of a screwdriver... not hard enough to break it. if that doesn't work you will likely have to take the carb apart and clean it.
My 'wing won't run unless it has been warmed up some. I would suggest that you r&r your carbs to make sure the jets in the bottom are working correctly. They tend to get plugged up, especially after sitting & the aluminum flaking off inside... Rick
Running well at high revs would indicate that all the fuel and air it needs are getting to the engine and you also have a good spark. Probably no problem with air and fuel filter ( if fitted) or sparkplugs.
Running hot, and bad idling are signs of a lean air fuel mixture. The engine is probably not getting enough fuel at low revs.
This could be caused by an air leak between the carburettors and the engine. Check that the vacuum line to the fuel tap is properly secured at both ends. It is behind the fuel line at the tap.
Get a a short length of hollow plastic tube and use it like a stethascope - put one end to your ear and move the other end around your carburettor mounts with your engine revs as low as you can get, and listen for any sucking noises that would indicate a leak. Look for cracks in the rubber inlets.
The other possibility is that there is an internal blockage in the idling jets or idling fuel circuit. This is where dirt tends to lodge because the jet dimensions and passageways are very fine - The high speed jets are much bigger and dirt often just passes straight through.
Try a little bit of choke while the engine is warm to see if you get a stronger low speed response. If so that would point to an internal blockage.
I am having a similiar problem. bmw r 1100 s will only start with full choke and will die if I cut off choke or give it any throttle. This is my first bike and it has been sitting in a garage for 2 years. I took out the carbs, cleaned them and rebuilt them. I didn't find any residual in the carbs and they were very clean. Today, I was able to get the bike running and took it down the neighborhood but after the bike warms up it idles at 6K! Man... If I can't find any answers from this forum, I will probably drop it off at the motorcycle shop just down the hill from me. Any suggestions anyone? I think I will try to drain the fuel and give it new gas. But still....