BACKFIRE WHEN THROTTLING DOWN

warren woodrow · Apr 15, 2019

424 runs pretty well . Has updraft carb. When it is running wide open and I THROTTLE DOWN HARD IT POPS SEVERAL TIMES THROUGH THE MUFFLER. WHAT CAUSES THIS ?

centash · Apr 15, 2019

Possibly running too lean, or running too hot. Shouldn't hurt much, just reduce the
rpms slowly.

Ben

Bob · Apr 15, 2019

An exhaust leak that allows air to enter the exhaust as you throttle down can cause/aggravate "backfiring".

Bob M · Apr 15, 2019

Pretty much normal for your tractor. The distributor has no vacuum advance to advance the spark under high manifold vacuum conditions (throttling down from full RPM).

Recommend check that idle timing is at spec, also that the centrifugal advance is working. Otherwise just ignore the backfiring - it will cause no harm.

Janicholson · Apr 15, 2019

As noted High vacuum operation decelerating down a hill or just closing the throttle. Unburned fuel in the exhaust is ignited by cylinder flame from a open
exhaust valve. Pow. Normal. Jim

warren woodrow · Apr 15, 2019

(quoted from post at 10:35:24 04/15/19) As noted High vacuum operation decelerating down a hill or just closing the throttle. Unburned fuel in the exhaust is ignited by cylinder flame from a open
exhaust valve. Pow. Normal. Jim

Thanks to all. I kind of like the sound of it, actually .

BACKFIRE WHEN THROTTLING DOWN

warren woodrow

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centash

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Bob

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Bob M

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Janicholson

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warren woodrow

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