Throttle hesitates early, and also stalls when trying idle-carb

How's the EGR Valve?

Have you looked at the TPS Sensor with a
scope, for bad spots or is it adjustable,that
you can do with a volt meter

The symptom sounds vacuum related

Is the exhaust converter as old as the truck?

O2 Sensor 100,000 miles or more?

Is the a MAP Sensor?

Clogged idle circuits in your carbs. Clean jets and passages.
You can try suck dirt out, therefore: Screw the idle mixture screw out ( almost totally ), give full throttle ( 1 second ) and then hold your hand against the carb air intake.
This will give maximum suction and can suck the dirt trough tje circuits.
Also, first drain the carb(s) to be shure there is no water in it...

Do the following

Here are the most common causes of idle surge, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake

This engine has automatic idle speed control, the computer controls a "air bypass" valve on the side of the throttle body where the air intake hose from the air cleaner is connected, the valve and the throttle butterfly get "sludged" up and this causes all kinds of idle problems and off idle stall, see full list below and fix for the problems

Here is the common cause of surges, cold stalls, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours.

To correct this problem Buy a can of throttle valve cleaner (it is made by CRC) from the local auto parts store, NEVER USE CARB CLEANING SPRAY, IT DESTROYS THE ANTI-STICK TEFLON COATING, spray it into the air intake through the throttle body of the engine until you have used about half the can, you will need to hold the idle up while you do this, it will try to stall, after this shut the engine down and disconnect the Negative (-) battery cable for 5 minutes. The intake is now clean, if you continue to have the idle speed control problems you may need to seek the help of a professional.

My best guess is gonna be a vaccum leak... pick up a cheap can of carb cleaner. Start your car and listen for a whistle or something close. it will probly be near or behind the throttle body. take your carb cleaner and spray it with out the little red hose around the back coner on the driver side of the motor. you can visually inspect the area after you hear an increase the idle. if you dont find it there spray all around any where you see a hose. Hope it helps. a vaccum leak usually wont set a check engine light on OBD 1 cars. Good luck.

Sounds like a possible throttle positioning sensor.

Sounds like you have a float sticking in your carburetor, is this a single carb or a duel carb? , also gas can go stale and your bike will run like **** if it also has been subjected to tank condensation and water in your gas, that also maybe your problem, I would drain the tank and drain the carb or carbs, and start off with fresh gas and would use 89 octane or better, also pickup some StarTron Enzyme gas treatment, it will stabilize your gas for up to 2 years, and remove the ethanol from your gas, that is a bad for your motor, try it you will never go without it. Good luck, Rick.

did u install new gaskets, the engine might be sucking air from outside the carbs. u can use a propane torch (not light) spray a little around outside of the carbs, see if engine sounds different, if it does... leaky gasket.. u might check there is no unplugged vaccum hose.

transfer ports could be pluged or ilde jet could use adjustment

Hi and welcome to FixYa,

Appreciate the direct "Ask Me".

Initially, pls confirm that it uses a two-stroke 50CC engine. Additionally, your description "It refuses to rev beyond idle speeds." could indicate several conditions:

• throttle up above idle speed, engine stalls/dies - fuel related issue, fuel starvation, clogged jets, nozzles, too much 2T oil, contaminated fuel (water). Basically a carb rebuilt;
• throttle up above idle speed, no change in engine RPM - mechanical problem, possible broken accelerator/throttle cable, stuck plunger in carb, detached needle valve;
• throttle up above idle speed, engine backfires/dies - electrical issue, check CDI, stators, trigger/pulse, their physical state/mounting, electrical connections;
• throttle up above idle speed, engine hesitates/flat spot - air/vacuum issue, check rubber coupling from carb to intake manifold, blocked or absent air filter.

Good luck and Thank you for using FixYa.

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