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The air/fuel mixture is Lean as opposed to rich.
Adjust the air/fuel mixture screw clockwise in quarter turns until the idle normalizes.
This screw can be found inbetween the carb and air filter. It should be a brass screw with a flat head (not cross or philips).
When you're almost out of fuel cab will go lean and therefore idle up.
Hi, M420blackbur it should be noted that the "AIR FUEL" mixture screw adjustment "ONLY" manages your idle and has no effect on any other circuit also any intake leaks must be repaired before the A/F adjustment procedure can be performed otherwise you will never obtain a proper idle and you will waste a lot of time chasing the impossible. The A/F mixture screw's purpose is to fine tune the fuel charge entering the combustion chamber. The following applies to both 2 and 4 stroke engines:
1. The mixture screw may be sealed at the factory with a Welch Plug please review the following video for removal. https://www.youtube.com/watch?v=wAXcksgvDkM
2. The mixture screw manages a range of 3 complete 360-degree counterclockwise turns from the bottom/closed position.
3. The mixture screw should have a spring and o-ring for tension and sealing integrity.
4. Turn the mixture screw clockwise until it gently bottoms out, this makes the fuel charge very lean and the engine should not idle if it does then the pilot/idle jet is too big and needs to be replaced with the next size smaller.
5. Turn the mixture screw 1 and 1/2 turns counterclockwise to establish a baseline for starting the engine.
6. To fine-tune the idle circuit, adjust the mixture screw 1/4 turn in or out to achieve maximum idle RPM, wait 15 seconds between each adjustment for the idle to settle.
7. Never go past 3 full turns out this will make the fuel charge rich, foul plugs, and produce black smoke out of the exhaust, if the engine RPM keeps increasing past 3 turns the pilot/idle jet is too small and needs to be replaced with the next size larger.
7. After achieving maximum idle back out the mixture screw another 1/8 of a turn then adjust the throttle cable idle stop screw to 950-1050 RPM.
8. This procedure works great on 99% of all engines, for the 1% that demand a more robust throttle response on aftermarket monster fuel delivery systems additional tweaking outside the box may be necessary.
For more information about your issue and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have a wonderful day. 2004 CR250 idle adjustment and air screw Life On 2 Wheels CR250 2002 2003 pdf http://www.partsfish.com/page/oem-parts-for-honda Honda CR250R Owner Manual Competition Handbook
firstly remove clutch cable at lever, put into gear and see if its hard to push and turns the engine over - if its easy with little resistance then the clutch isnt releasing fully. check the pressure plate springs on clutch unit making sure the plates are squeezed up tight together and that centre hub is located correctly. if it is hard to push then check cable adjustment. hope this helps
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. < < 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. Please rate this solution. Thanks!
if there is a spark mate there is something wrong with the fuel side of things your gettin a spark but no fuel in cylinder take carb off and strip it down cleaning it out also cleaning airfilter and adjust float to the manuals specifications just bend the metal the little valve is on also adjust the mixture screw this will be a screw on the outside of the carb there are 2 idle and mixture the idle will be the furthest out you want the mixture in the manual it will say something like 2/12 screws out this means screw it right in till it gets tight then unscrew it the amount of turns good luck buddy