I recently had a couple of Tecumseh motors doing the same thing. Mine was just a carb adjustment, the jet was turned in way to lean so adding choke would help it suck in fuel. I would run it with the choke on, then back out the screw on on the carb til it runs a little rough, then reduce the choke. Do that same thing until it is running good with the choke off. Doing this will greatly increase your power when the motor is under a load.
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Re: runs on choke,why?
The engine is running on choke because the jets are probably clogged in the carburetors.Some of the newer carburators have very little in the way of adjustment and it is usually cheaper to replace the whole carbthan to try and fix it. Tip : Always use premium gas with no ethanol in any small engine. Ethanol blend gas has ruined more small engines than I can remember. Especially ones that sit for an extended period of time ( like a snow blower). I also recommend add Stabil or Seafoam or any good quality fuel stabilizer to the fuel tank of all small engines. Hope this helps.
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sounds like carburator. probably to lean. Try varying degrees of choke and see if it will clean up.If so you are running to lean and might just need to adjust jet screw outward.If it gets worse with choke your to lean and adjust screw inward.
Believe it or not you just said the solution to your own problem manufacturers specs requires for any adjustments to engine idle or other carburator adjustments to be preformed while the engine is idling and at normal operating temp in plain english let the car warm up then make your idle and mixture adjustments if this doesnt solve it i would check the auto choke and make sure it is opening at normal operating temp hope this helps good luck
More than likely, the idle (pilot) jet is partially clogged. This is common when it will idle fine with the choke on, but won't idle without it. Sometimes a fuel treatment will clean the carburator, but not usually successful in cleaning the idle jet. Usually it requires removing the carburator bowl and and cleaning with the use of a gauge wire. The idle jet is usually recessed (next to the main jet).
A good video to show a generic carburator rebuild can be found at this link: http://www.youtube.com/watch?v=exa467_eoXw The guy goes through a pretty detailed description while going throught the process. The carburator will not look exactly like yours, but it will be similar internally.
It's a carburated bike. You need to have your carburator cleaned. It's not a difficult job, howver if you are not comfortable with what your doing a shop will charge a half hour or 1 hour o clean it for you on average.
Your carborator mixes your fuel and air. when the bike is at idle it is only getting fuel from the "idle" needle. The smallest needle in the carb. These needles are hollow. As fuel sits in the carburator for a long period of time (over 2 weeks) then the fuel can gum up and clog the neeedle. If it runs when the choke is on but dies when you take it off the choke this is what is happening:
On some bikes a "choke" doesn't actually choke it of fuel, sometimes it actually enrichens it. Your bike is probably set up to open another passage way besides the "idle" needle allowing fuel to go into the engine from another passage. you shut the "choke" off and now it only has the idle needle to get fuel from. If that's clogged the bike dies.
A can of carb clean and a screw driver is usually all you need to clean a carb. But if done wrong you will pay more to have a pro fix it.
should adjust the butterfly to about 3/8" opening at 50 degrees farenheit when engine is cold. Usually about 1 mark to the lean side on the choke spring housing. If unsure set the choke to the center mark than richen up one mark at a time until the engine starts and idles up when cold after properly setting choke by fully depressing and releasing the accelerator before cranking. If it doesn't idle up enough turn up the fast idle screw 1/2 turn at a time. Another common problem with the YFA is the choke heat riser tube rusting off at the manifold and the choke not unloading when the engine warms. Install a new riser tube after using a drill bit the same diameter as the tube to drill out the remainder of the old tube in manifold before inserting the new tube and attaching to choke housing.
look on the carburetor. there will be 2 screws right beside eachother. one is an idle jet and the other is the main jet. if you want faster or slower idle speeds, adjust idle jet. if you want more power, adjust the main jet. you have to get them set just right . they might smoke a little bit because you are throwing more fuel to it which means you are getting a richer mix
The carburator needs to be adjusted a little, thin our your mixture screw when the trimmer is warmed up and idling. Well how do you get it to idle? I usually have to play with the choke lever with the throttle wide open going from choke to partial choke as needed to keep it running. Adjusting can be tricky, you need a small screwdriver. Screw all the way in then back out 3 to 3.5 turns. this should get you close. Adjust idle as needed.
this prob happens allways in carburated engines that the car or motorcycle is running lean or rich . because the air - fuel mixture ratio is not right . so you should open the carburator and remove the air filter you will find two screws in the lower front section of your caeburator. you can adjust them by a screw driver until your car is smooth
Before you start check the status of your choke. One that is stuck on will cause a high idle. If the choke checks out, proceed to the following:
You should have what's called a 2 needle carburetor. A larger screw adjustment for idle, and a smaller for high speed.
Start by adjusting your low speed (idle) needle until you reach the desired idle. I prefer about 850rpms. Do this with the engine running and adequately warmed so that your adjustments are not thrown off by the automatic choke.
Next slowly open up the high speed needle. As you open it your idle speed will gradually increase. Adust it in 1/8 turn increments, pausing after each adjustment to allow the changes to take affect. Keep opening it until you stop increasing your rpms, then take it back 1/8 of a turn.
Next readjust your idle mixture screw so that your idle is back down to 850rpms.