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Registered
Join Date: Dec 2005
Posts: 3,384
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Holy Sparks Out Of The Carb Bat Man!
Hey guys. So I got this 912 that had a broken valve adjusting screw. I replaced that screw and adjusted the valves. Then it was still running poorly so I took apart the carbs and they were nasty. Cleaned and rebuilt them, reinstalled them and now I have sparks coming out of a carb barrell. Its the cylinder on the passenger side near the firewall. Now I installed new plugs also. So what could it be? I set timing at 28 degrees, should I go to 30 degrees? Could I have adjusted the valves on that cylinder wrong? Just for reference, I adjusted the carbs by screwing the big roung plastic knobs on the base of the carbs in all the way and then out 1 full turn, when I did 1.5 turns out as specified there was a ton of black smoke. So what do I do to stop the sparks from occuring and have it run correctly?
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04-14-2006, 08:52 AM
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Registered
Join Date: Oct 2005
Location: Arvada, Colo
Posts: 85
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flames back thru the carbs usually indicate a timming problem however a lean carb mixture can do that as well if the engine is cold. A grossly misadjusted ( or bent ) intake valve that is not seating properly could also be the culprit. Spark `crossfire` inside a dirty distributor cap could cause the same situation.
If the carbs were as `nasty` as you suggest I would clean out all the idle jets..... it doesn`t take much to clog one........... which could make adjusting the mixture screws damn near impossible.................. A lean idle setting will cause popping back thru the carb at idle when the engine is cold. good luck, Jeff |
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04-14-2006, 09:32 AM
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Join Date: Dec 2005
Posts: 3,384
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Well could a leaking intake gasket be the culprit? I think I have that condition also as I had to cut a gasket out of a sheet of pond liner that I was missing and its thinner than the rest of the gaskets?
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04-14-2006, 10:26 AM
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Join Date: Oct 2005
Location: Arvada, Colo
Posts: 85
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If you have an intake air leak you will be chasing a good idle....both speed and mixture. Jeff
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04-14-2006, 05:35 PM
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Registered
Join Date: Jan 2002
Location: UK, Derbyshire
Posts: 152
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Quote:
 As Jeff says I'm also getting popping/backfiring up through my carbs, although mine are like new. Most likely timing or as Jeff says a lean mixture. I have the car booked in at a rolling road to get the carbs and everything setup just so. This should solve my problems. You should never use pond liner on a Porsche  It might also melt when it gets up to temp!! That will give you even more problems
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04-15-2006, 08:14 AM
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