When u turn off the choke, it opens the butterfly completely, causing more air to flow, if the gas flow dose not, or can not increase enough to meet- the increased air flow when the choke is off it can not run. Fix, gas flow must be broth back to requirements.
A2
If an engine will not run unless the choke is on, it indicates that the carburettor is not mixing the fuel/air correctly, not enough fuel, or too much air. This is most likely caused by a blocked jet. it could also be caused by an air leak between the carb and cylinder.
It could be the slow running jet, or the emulsion tube.
The best remedial action is to strip the carb and clean it.
I'm not familiar with the Yamaha carb, but you may get away with removing the jets externally and blowing them through.
Does it run on choke? Is it starving for fuel, if so is the needle valve set for the float?
I asked this question before I signed in
Your Briggs and Stratton 5.5hp only runs with the choke on because it needs a tune up.
You probably have a plugged pilot jet caused by sitting with bad gas for more than six months without running
You can run only gasoline with 5% Ethanol no more which means no E85.
i have a Yamaha golf cartserial# jg5-315607 the cart was starving for fuel and not running properly cleaned the carbchecked the lines and the 3 way valve the cart will only run when i pull the choke then of course it smokes as it is to rich. on the flat area it will run okay asmall ioncline i have to pull the choke this is a gas engine . would there be a electronic governor on this cart if so where is it also is there a gas filter in the tank? i do not know the year
You might check your primer bulb. Mine was cracked and the only way it would run was with the choke on about half way. I changed the primer bulb -- problem solved. Hope this helps.
You have a plugged piolet jet. The carbs need to be gone through
Standard is full choke first, then half-choke for a couple of minutes, then run.
the bike is running lean, check that the air filter has oil and a good seal, or the idle screw needs adjusting or your carb needs cleaning or and this is a strech... you have a hole in the tip of the piston, I would check them in that order.
Obviously a weak mixture, as using the choke makes the mixture richer. Quite possibly there's an air leak between the carburettor and manifold
As far as my nowledge there is not one.the only way there could be is to run off the starter but i have owned a good handfull of Yamaha 450 and the wr450 nor the yz450 have revers.