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BACKFIRE WHEN THROTTLING DOWN


 
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warren woodrow
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Joined: 21 Oct 2018
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PostPosted: Mon Apr 15, 2019 8:12 am    Post subject: BACKFIRE WHEN THROTTLING DOWN Reply to specific post Reply with quote

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 ?
 
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centash
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Joined: 01 Nov 2014
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Location: southern ontario canada

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PostPosted: Mon Apr 15, 2019 8:32 am    Post subject: Re: BACKFIRE WHEN THROTTLING DOWN Reply to specific post Reply with quote

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

Ben
 
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Bob
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PostPosted: Mon Apr 15, 2019 8:41 am    Post subject: Re: BACKFIRE WHEN THROTTLING DOWN Reply to specific post Reply with quote

An exhaust leak that allows air to enter the exhaust as you throttle down can cause/aggravate "backfiring".
 
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Bob M
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Location: Chili, NY

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PostPosted: Mon Apr 15, 2019 9:15 am    Post subject: Re: BACKFIRE WHEN THROTTLING DOWN Reply to specific post Reply with quote

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.
 
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Janicholson
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PostPosted: Mon Apr 15, 2019 9:35 am    Post subject: Re: BACKFIRE WHEN THROTTLING DOWN Reply to specific post Reply with quote

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
 
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warren woodrow
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PostPosted: Mon Apr 15, 2019 12:40 pm    Post subject: Re: BACKFIRE WHEN THROTTLING DOWN Reply to specific post Reply with quote

CVPost-Janicholson wrote:
(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 .
 
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