engine backfire

1971 VOLKSWAGEN BEETLE
20,000 MILES
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BMWGENE
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  • 1 POST
rebuilt 2010 cc twin weber 40mm carbs.hi flow exaust sys d.u.i. dist. when leting off gas slowing down in 4th gear engine backfires (loud) small increase on gas pedal stops backfiring. adj. timing no effect, adj carbs ,richer or leaner no effect. engine idles ok,runs perfect up thru the gears. p.s. adj valves no effect. thanks gene
Sep 11, 2011 at 8:03 PM
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PROMECHANIC
  • ✓ASE Certified Mechanic
  • 536 POSTS
  • ASE Certified Mechanic
Most backfiring is caused by timing issues or fuel issues. Since you have checked all of that I would have to suspect an exhaust leak.
Did it back fire before you installed all of the things you mentioned?
Sep 11, 2011 at 8:37 PM
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