My honda qr 50 bike starts and revs for a few seconds then dies out. i cleaned the carb. checked air box etc.

SOURCE: rebuilt carbs-starts and idles but wont rev up without choke on

sounds like the main jets are partly pluged, you must remve all brass jets and seats including needle jet and its slide soak in carb cleaner and blow out with compressed air only.. hold up to bright light to verify if all are clean. jim

SOURCE: bike wont start

Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two screws down. Only screw these in until they LIGHTLY seat. Now turn each screw one and one half turns outward. Clean the air filter. Install a new stock NGK spark plug.

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SOURCE: when start go to rev it just dies

Remove the throttle stop adjuster and the air screw adjuster and spray carb cleaner in the holes.
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. Turn the pilot screw 1/4 turn counter clockwise. Check the float level. Before putting the slide back in the throat of the carb, move the clip on the jet needle one notch lower.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. Adjust the idle speed with the Throttle stop screw. This process should get you back on the road. A “very helpful” rating for this answer? Thanks!

SOURCE: Honda 160cc mower engine starts and dies.

Your carbeurator is crudded up. Get a can of aerosol carbeurator cleaner at any auto parts store. Remove the air filter and spray two squirts of cleaner into the air intake. Start the engine and keep it running by squirting more carb. cleaner into the air intake. WIth a little patience you will clean your carb. and solve your problem.

SOURCE: Honda CG125 stalls when choke closed

Hi mate, what you want to do is take a dump in the petrol tank. This usually cleans the carb out with your **** and works surprisingly well.