Backfiring fix PLEASE!!

[frodrummer]

81 2pg. I have tried adjusting my trusty "click-pen spring" a hundred different times. Have also adjusted the float, replaced filters, and put fresh fuel in. It ONLY backfires when starting cold. After feathering the choke, and driving around the yard just long enough to get warmed up, it will stop/start easily without backfiring. I want to find a fix before I blow out a seal.

Could I be missing something with the microswitch?

I don't know what else to try.

[Bellahmatt]

I had the same problem after I found out about the "click pen spring" after I installed it it still backfired until it warmed up. I recently decided to install a stiffer spring and it fixed the problem. It held the the throttle flap shut completely and still gave me full throttle !


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[redcloud]

Have you checked your throttle cable? If your cable is to tight, it could be holding the plate near open and not allowing the pen spring to take over the close. When it warms up, the throttle cable could be loose enough to not be a problem. Just a thought.

[racin161]

Bellahmatt has it right Go to a stiffer spring and really load it firm on the throttle shaft arm. I to had a slight backfire with the stiffer spring until I loaded the crap out of it by adjusting the throttle cable to incress the load. FIXED !!!!

LOU

[Dave Box]

Just to be exact, are you saying that the backfire only occurs when you are starting the engine when it is cold? The most common backfiring is when you back off the throttle and then try to accelerate and that is when the throttle spring adjustment comes into play.

If my first sentence is correct then I would make a wild guess and suggest that your exhaust manifold gasket is worn (and two strokes are very hard on gaskets) and has a slight leak which is allowing air in. As the exhaust warms up it expands and closes the gap, no more air leak and no more backfiring.

Of course I could be wrong it has been known.

Dave

[frodrummer]

Originally Posted by Bellahmatt

I had the same problem after I found out about the "click pen spring" after I installed it it still backfired until it warmed up. I recently decided to install a stiffer spring and it fixed the problem. It held the the throttle flap shut completely and still gave me full throttle !


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Would doubling up two click pen springs stiffen things up? I have an abundance of them. It seems no matter how tight I pull the throttle cable (while adjusting the spring), the throttle arm still moves slightly before the microswitch clicks. Could this be an adjustment issue with the microswitch?

Dave, yes it only backfires when starting cold (even in warm weather). I have never had it backfire after pressing/depressing throttle while in motion.

[Dave Box]

In that case I concur with your findings that messing with the throttle spring will not fix it. At this stage I would buy a a set of exhaust gaskets and see what happens.

Dave