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knighty2 Alfa Arna
Joined: 19 Aug 2009 Posts: 11
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Posted: Thu Sep 23, 2010 10:58 am Post subject: backfire / popping from exhaust - 40mm dellortos |
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Hi Folks - recently my beach buggys engine (a 1.7 hydraulic from a G plate 33, with 40mm dellortos) is starting to pop and bang a bit when crusing at low speed, less than 3000rpm, it really does sound like neat fuel is dripping into the exhaust.........I have also had a few instances where it dosent want to rev over 3000rpm, and I found that after removing the main jets and blowing them out it would run fine, found a bit of crap in one of the jets on one occasion.........I'm suspecting two things:
1) perhaps the carbs have ingested some contamination either from the fuel or air system???..... or perhaps some of the internal carb diaphrams are breaking up???
2) the carbs perhaps need a re-build........if so what areas would you lot say are focal suspect points considering my symptoms above. |
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Oggie Green Cloverleaf
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Joined: 06 Mar 2008 Posts: 811 Location: Whitehill
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Posted: Thu Sep 23, 2010 9:00 pm Post subject: |
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Possibly an idle jet is blocked. I have had this a few times and the car sounds more like a Subaru engine , revs fine but won't sit comfortably at any steady revs. Also exhaust leaks can cause popping sound as air is drawn in through cracks. _________________ PHAT 33 |
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paulhide P4
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Joined: 20 Dec 2003 Posts: 1607 Location: Oh Beautiful Billingham
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Posted: Thu Sep 23, 2010 10:29 pm Post subject: |
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Hi Knighty, where the fuel pipes enter the carbs there is a circular filter behind the big nut (17mm?) on each carb. See if there is any crud accumulating there. Do you have an inline paper filter fitted on the fuel line?
A bit of popping and banging just means the mixture is a little too lean or rich, but not revving over 3000 is not so great - problems with idle jets would only cause problems beneath 3000 revs. Above points to main circuit blockage or electrical fault. _________________ Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188 |
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