FIREBALL is out of control !

[oldmeatwad]

Looking for suggestions for the following condition for my PRD fireball 125:

Condition

• Starts right up – no issues there
• Seams to be running fine on its own
• Dies anywhere from 30 – 60 seconds unless I play the game of throttle blipping and holding my hand on and off the airbox ports.
• Can duplicate the same behavior 100% of the time

Whats been done

• Full carb rebuild – No change
• Set H / L mixture/idle screws per PRDs specs (adjusted a bit back and forth also – no help)
• Inspected reeds – No issues noted
• Fresh high octane fuel
• Fully charged battery
• Inspected and cleaned plug (1 month old)

To me its smelling very much like somethings gone wacky with the carb, but I am looking for advice as the behavior is the same all the time.

ALL HELP WELCOME!!!

BONUS ISSUE – My throttle line is sticking. I replaced it (new cable and sleeve), routed it so there are no kinks in it and yet it seams like the carb does not have a strong enough spring to return the throttle to idle. Do the return springs onTillotsons go bad and cause that condition? With the cable off, the butterfly seems to work fine. As soon as the cable is on, it sticks (old and new cable).

Before I knew it was sticking open,  I started it, the PRD redlined and I had to pull the fuel line to stop it – TOTAL runaway condition – did not respond to the easystart off button or pulling both leads on the battery. THAT’s DAM scary if that ever happened on the track.

Anyway – these issues have kept us off the track all season and now its VERY agitating.  I’m also open to trailer it to a mechanic in NJ if anyone can recommend someone…..just need to be on the track again ASAP !

 

Thanks!

 

 

 

 

[Ric mcDade]

I would look at fuel delivery first, make sure tank is clean, take any fuel filters out of the equation, fill your tank and then pull the line from the carb and let in drain in a can, make sure the stream is large and consistent. If it is, then take a second look inside the carb and make sure you don’t have anything upside down or backwards. Ck your reed block/ carb, and make sure your pulse holes are line up and you don’t have a gasket blocking it.On your throttle, you need a return spring on your pedal, and not just the carb.

[oldmeatwad]

Thanks Ric. Will give it a go and see if it improves.

[Jim Derrig]

My WAG is that you’ve flipped the relationship between the gaskets and the diaphragms on the carb.  The gaskets go on the bottom (closer to the ground when carb is installed) and the diaphragms go on top.  If that’s not it, there could be an air leak, such as from a bad mixture screw gasket.

Once you’re convinced that the fuel path is rock solid, the next culprit is a weak spark from a bad stator (though my experience is with Leopards and not PRD’s)

[oldmeatwad]

Hmmmmm – Going to check that because I believe i placed the diaphragm and then the gasket.  I remember this as I though it odd but the diagram was clearly showing it in that order. Going to pay close attention this time. One I verify it, Ill reassemble and look to Rics suggestions.

BTW – should the fuel line be completely without air bubbles? I notice that I get what looks like solid fuel connecting in the line near the carb, but near the fuel tank, there seams to be a dry spot. I discounted it as there always seams to be fuel in the line where it counts.

 

 

[Ric mcDade]

Make sure you tie wrap the fuel line at all connections, but I get minor air bubbles too

[oldmeatwad]

Got sick of playing with it. Installed a new carb and problem is 100% solved. Thanks for everyone’s advice!

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