2003 yamaha blaster will not idle and surges hard at a slow mph?

Question

I can't get the thing to idle no matter where I turn the s***w under the seat, also when at a slow speed it cuts in and out, it's not a random cut in and out it's steady.revs up a little then cuts out for a second revs up cuts out. when hard on the throttle there is no problem.

Also I am not fimiliar with the mechanism on top of this carb. What is it called and what's it's function. Thanks

Answer 1

thats a oil injector, a special feature. Could be the reeds or cdi box or injector (It is a 2 stroke). better to bring to dealer

Answer 2

Some things which will cause the erratic idle & low speed running:

*Air Leaks at anywhere in the intake system

-reed gaskets

-carb mount hose

-cylinder base gasket

-crank seals

A Carb with plugged up low speed jets can do that,,,but usually after attempts are made to "adjust " the carb for the odd running.

The lump-o-stuff bolted on top of carb is what Yamaha calls TORS.

Throttle Over Ride System.

It's a "safety feature" so that If Throttle gets stuck,it shuts down the engine.

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To check for air leaks,,,WD-40 works OK.

While engine is running ,,,spray some WD40 around where plugs into intake manifold.And around Reed Gaskets,,Cylinder Base,etc.

You can also Wiggle.Tug on Carb a Little---if that rubber manifold is craked or split,,that will make it open  and run Really weird,or die.

The premise is,,,any air leak causes extreme Lean fuel mixture at idle.

The Propellant in WD40 is Propane,,,and some of the liquid is a sort of Kerosine,,,thus a Fuel itself.

It's presence adds fuel to the overly Lean system to "compensate" for the excess air.

Which will immediately CHANGE the way the engine is running.

An engine with everything intact & working right will NOT respond to getting sprayed w/ WD40.

On which is leaking air,,,will respond soon as WD40 hits the leak.

Starting Fluid,,"ETHER" is Dangerous to use----very easy to start a fire.

A Propane Torch is generally safe---Not LIT of course,,,just the propane discharge.

That's my best guess from the symptoms you describe,,,an air leak somewhere in the intake system.

Good Luck,,,and be Careful