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Old 10-14-2018, 10:59 PM   #39
Rich in Tucson
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Join Date: May 2010
Location: Tucson, Arizona
Posts: 368
Default Re: Terriable backfiring

Just fixed one like yours. Idled great, would run several quarters of a mile then sputter and backfire. Then start right up and repeat as you waited to get back into traffic.

Gas flow to carb was a dribble from disconnected fuel line. Blew air into tank from gas line and found high resistance (~15 psi to overcome). Checked screen in gas sediment bulb = clean. Disconnected interior gas line (was a repro fat one) and found it packed full of rust like coffee grounds.

About 12 weeks ago the leaky fuel shut off valve was replaced with an Ace Hardware ball valve complete with yellow natural gas teflon tape sealant and the stand-up in-tank filter was removed opening the floodgates for years worth of crud to descend into the fuel system and reduce flow to a trickle good enough for idle but not for go.

I have replaced a lot of corroded/dissolved/and as a result plugged in-tank filters and cursed them all the while but they do serve a useful purpose if they are installed AS A CONSUMABLE MAINTENANCE ITEM (around here 3-5 years is pushing it for trouble) and not a permanent fix.
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