91 cr 250 r i cant keep my bike running for few min and dies out

The problem is the needle valve in your carb is partially clogged. It's not letting enough gas into your carb fast enough. You let it sit for 10 mins and it slowly fills the carb's bowl back up. Then you ride it and it empties the bowl of gas faster than the needle valve can keep it full and the snowmobile dies. Get the carb cleaned and it will fix your problem

It sounds like you have some debris or water in the carberator. You can drain the bowl easily depending on the style of carb. Most newer units take a 7/16 or 1/2 inch opened end wrench and just loosen the bowl bolt or valve whichever it might be until you get fuel or fluid flow. If there is water or other debris I recommend dumping the tank and flushing the fuel system with a good carb cleaner.

how little is the spark, is the spark plug ok, more information please

You need to check the fuel filter -- follow the fuel line from the tank down to the filter, should be tucked in below the seat..

clean out fuel tank and lines, fuel filter and carb with carb cleaner. carful not to adjust settings,just clean them.fresh fuel

This is usually the symptom when water has condensed in the gas tank and made it's way into the float bowl. Drain the carbs. No guarantees, but no money is spent on the suggested fix. Hope this helps.

Remove the water trap bowl at the bottom of the petcock, (gas valve). Is there any water or trash in the bowl? Drain a cup of gas from the tank. Is there any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ).

Drain the carburetor. There should be a screw on the lower side or bottom of the carb float bowl. Remove the screw then replace it after the fuel drains. Turn the gas back on and wait a minute for the carb to fill with gas. Install a new stock NGK spark plug and try to start the engine. If the bike doesn't start and run properly then shut off the gas and remove the carburetor from the engine.

Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Remove the idle screw and the air screw on the outside throat of the carb and spray into the screw holes as well.
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Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two adjusters down. Only screw these in until they LIGHTLY seat. Now turn each adjuster one and one half turns outward. Put the rest of the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine.

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ALWAYS have a fire extinguisher on hand when working on carburetors.
Remove the water trap bowl at the bottom of the petcock, (gas valve). Is there any water or trash in the bowl? Drain a cup of gas from the tank. Is there any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ).

Drain the carburetor. There should be a screw on the bottom of the carb float bowl. Remove the screw then replace it after the fuel drains. Turn the gas back on and wait a minute for the carb to fill with gas. If the bike doesn't start and run properly then shut off the gas and remove the carburetor from the engine.

Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Remove the idle screw on the outside throat of the carb and the air screw on the back left of the carb bore as seen from the filter. Spray into the screw holes as well.
< < READ CLOSELY > >
Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two adjusters down. Only screw these in until they LIGHTLY seat. Now turn each adjuster one and one half turns outward. Put the rest of the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine. This process should get you back on the road.

The carb has a diaphragm fuel primer pump Each time the throttle is cracked open the pump give a shot of gas. This is fine for take off but downshifting can create a rich mix. A rich mix promotes backfire. Just don't crack the throttle.

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Sounds like there may be trash in the carb. when the gas bowl is full it runs until the gas runs out then it dies. Take the breather off get it started and then put you hand over the intake on the carb. sometimes this will allow the trash to be sucked on through do this several times take your hand off before the motor shuts down and then do it again until you clear it up. If this does not fix the problem you can take the bowl off the carb an see if it is getting fuel with the float hanging down this opens up the needle valve to let gas fill the bowl. there should be a steady stream of gas coming out. when the bowl fills up the float floats up and closes the needle valve. If there is not a steady stream of fuel coming out with the float hanging down with the bowl off you may have to remove the float and needle valve and clean out the needle valve jet with something like a sewing needle. If you are getting gas steady and fire to the plug it should run.

I have an 06 cr 250. I used to mix my fuel at 32:1 and it ran fine for a year or so as of late it's been fouling plugs every single ride. I've ridden 2-strokes all my life and know how to ride the powerband but lately its been spitting oil out of every seam in the exhaust. It used to maybe have a couple drops after a ride out the end of the pipe but now its leaking from the connection from the case, the pipe to muffler connection and a lot out the back of the muffler. i switched to 40:1 about a month ago and that's what is happening, i couldnt imagine what it'd be like if i left it at 32:1. I took the carb out and looked at my jet sizes, they are both a size smaller than stock. Any help? Also, the bike is so tempermental that I have to have all my gear on when i start the bike because I cant take my hand off the throttle for even a second or else the bike will foul the plug and die literally within 2 seconds. I know they arent meant to idle but its kinda extreme. my friend has a 2005 cr 250 and mixes 32:1 has no problem, can start his bike on the stand and walk away from it for 5 mins and put his gear on.it'd idle for at least 10 min before it'd die, but he'll kick it and it'd start right back up. I've heard running bean oil would help, but I've also heard it has a tendancy to seize up the rings? any truth in that? ,I would try more gas in your mixture, before you start changing everything. Its all in the way your ride, some people can do 32:1, some 40:1(me), some 50:1. ,,,