03 yamaha yz250f runs with choke on but wont idle with choke off

The damage is already done. Gasoline breaks down within 1 year. Drain and flush the old fuel out of the gas tank(s). Try adding Chevron Techron fuel injection cleaner to the replacement gas. That may work. However, you probably need to remove all the fuel injectors [if it's a fuel injected engine] and have them sent out to be professionally [ultrasonic] cleaned and tested. Fords are notorious for fuel injector problems. Also do a fuel system pressure test, as the bad gas may have damaged the electric fuel pump [located in the fuel tank(s). For a carbureted engine, you will need to have the carburetor overhauled or replaced with a rebuilt unit. NEVER let a vehicle sit unused for more than 6 months without first treating the gasoline. I always add a fuel stabilization product like Sta-Bil to the fuel, if the engine will not be run for at least 2 months or more. Adding these products after the fuel has gone bad [is already old] will not help. Then it's to late. Below is a link for Sta-Bil. I've used this product for over 20 years. It will save a LOT of grief, when storing vehicles or gas powered lawn equipment. See



jap=1t2&jkId=gpt:pt_134962&js=1&jsid=34339&jt=1&jr=http://shop.advanceautoparts.com/p/sta-bil-ethanol-treatment-22264/10057636-P%3Fcm_mmc%3DACQ-_-Google-_-Enhanced-_-Dynamic#utm_source=acq&utm_medium=google&utm_campaign=enhanced&utm_content=dynamic">Sta Bil Ethanol Treatment 22264 Advance Auto Parts

Install a new spark plug

Clean or replace the air filter

Use only gas that is no more than 2 months old
& add fuel conditioner such as Sta-Bil or B&S,
unless you have to mix fuel for a 2 cycle motor

Once running & fully warm,adjust carb screws for
fuel mix at idle & fast rpm, then set the idle

Check for spark with a small engine tool avail for that
It looks like a spark plug with a clip on it & avail many places

May have to remove the carb,clean it & install a new kit,if
you still have problems

Check for spark at the sparkplug by pulling the plug wire from the plug, now insert a phillips head screwdriver into the plug wire and hold by the handle so that the screwdriver is about 3/8 to 1/2 inch from the cylinder head or bolt. Have someone crank the engine and check to see if it sparks. If you have a good blue spark then that's a good thing. Next replace the spark plug with a new one. Spark plugs corrode when sitting in an engine for a long time and loose their ability to spark under compression, especially when they have been run for a whole summer. If this doesn't get your mower started, buy a can of Sta-bil. This is a brand name varnish and gel remover. Mix a little on the strong side and make sure to shake the unit to mix the fuel and Sta-bil. I usually mix a few ounces of gas and Sta-bil in a small squeeze bottle. Then I remove the fuel line and fill the carb and fuel line with this solution, which I mix about 1/2 ounce of, to the 2 ounces of fuel. Crank it over after replacing fuel line and see if it starts. Make sure the choke is on full, it will help it stay running till the mix does its job. Then close choke slowly. If need be get back to me with the Model number, series and year. Good luck I hope this solves your problem. Please post a solved comment on fixya, so I receive credit for the solve. This will increase my ranking on fixya.com That is how I get paid. By knowing I am helping someone!!!!

Check for spark at the sparkplug by pulling the plug wire from the plug, now insert a phillips head screwdriver into the plug wire and hold by the handle so that the screwdriver is about 3/8 to 1/2 inch from the cylinder head or bolt. Have someone crank the engine and check to see if it sparks. If you have a good blue spark then that's a good thing. Next replace the spark plug with a new one. Spark plugs corrode when sitting in an engine for a long time and loose their ability to spark under compression, especially when they have been run for a whole summer. If this doesn't get your mower started, buy a can of Sta-bil. This is a brand name varnish and gel remover. Mix a little on the strong side and make sure to shake the unit to mix the fuel and Sta-bil. I usually mix a few ounces of gas and Sta-bil in a small squeeze bottle. Then I remove the fuel line and fill the carb and fuel line with this solution, which I mix about 1/2 ounce of, to the 2 ounces of fuel. Crank it over after replacing fuel line and see if it starts. Make sure the choke is on full, it will help it stay running till the mix does its job. Then close choke slowly. If need be get back to me with the Model number, series and year. Good luck I hope this solves your problem. Please post a solved comment on fixya, so I receive credit for the solve. This will increase my ranking on fixya.com That is how I get paid. By knowing I am helping someone!!!!

Head Gasket

Intake Gasket

Hello,

Anytime a bike sits for an extended period of time, it is a good idea to drain all the fuel out of the system and add Sta-bil when filling up with fresh fuel. Also, the rings and seals need time to re-seat themselves. This could take, up to, three days.

You should do an oil and filter change.

After running a tank through, with the Sta-bil added, the system, buy a can of Sea Foam and add the recommended amount according to the directions.

This should clear up the issues you are having.

Hope this helps. If you find this information helpful, please vote on this post.

Regards,

Oz

Well after you clean it out and get it running make sure you dump some sta-bil into the gas tank next time it is going to sit idle for over 3 months. the gas turns into a shellac which glues up the carburetor.

sounds like the carburetor's getting plugged up. First, sta-bil doesn't burn that great, so you may want to dump it and start over. If the fuel has already sat for that long, sta-bil won't help it anyways. You want to start with fresh gas, with the proper mixture. If that doesn't solve it, you can look at the wide open mixture screw and see if you can tune it better.