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Mrunyan2001
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PostPosted: Sun May 02, 2021 5:27 pm    Post subject: Missing? Reply with quote

Got a new 1641cc, 110 cam bought some new 40 mm brosol/solex dual carbs. Sync them several times. Runs great off idle. After creeping chugging along starts missing. Like dirt in carbs but it's all new and clean clears out about 20 mins and runs great again. Is new fuel pump causing to much fuel pressure? My gage doesn't go that low. I do have black sediment out of exhaust[/list]
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oprn
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PostPosted: Mon May 03, 2021 3:15 am    Post subject: Re: Missing? Reply with quote

Not much to go on but it does sound like it is too rich. Yes those carbs are sensitive to too much fuel pump pressure in my experiance. I reduced it to 1.5 psi on mine and they ran much better.
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Mrunyan2001
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PostPosted: Mon May 03, 2021 4:58 pm    Post subject: Re: Missing? Reply with quote

Thanks, I reduced to 2 lbs. See what it does. I still have a hint of darkness out of tailpipe when goosing throttle at idle. My timing is set about 28-30 degrees. I may try to advance it a little more and see how it goes.
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dustymojave
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PostPosted: Sun May 09, 2021 7:42 pm    Post subject: Re: Missing? Reply with quote

Note that a carbureted old school engine like a VW Bug will NOT run as clean out the exhaust as a modern computer controlled, electronic fuel injected, O2 feedback sensor, catalytic converter equipped car with another 50 years of technology in it than your Bug. Most of those so equipped will NOT be as fun to work on and drive as your Bug.

Not sure how you goose your throttle while idling. I think you mean goosing the throttle FROM idle. Carburetors have accelerator pumps that make the fuel mixture richer when you "goose" it. An engine NEEDS more fuel to increase speed. But in the Bug it's NOT controlled nearly as closely as the increase in fuel ratio in one of the computer EFI cars mentioned above. Nor does the Bug have 13 feet of exhaust pipe to conceal what comes out of it. The exhaust comes out right next to the engine that you are goosing. In a Honda Accord, it's at the other end of the car
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L5wolvesf
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PostPosted: Sun May 09, 2021 8:01 pm    Post subject: Re: Missing? Reply with quote

If you were running over 2.5 psi fuel pressure you should recheck your float setting and the top gasket.

Also, were the carbs ever really tuned?
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Mrunyan2001
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PostPosted: Wed May 12, 2021 5:24 pm    Post subject: Re: Missing? Reply with quote

I dropped pressure to 2psi resync them. I noticed from factory the accelerator pump on left carb was adjusted more about 3mm more. I turned it out to allow it to move about 5mm like the other side. Running pretty bad now. I've run buggies my whole life. My first dual carb. Very aggrevating .. The top gaskets do seem a little wet. Are you saying I need to replace needle seat and top gasket due to over 4 psi fuel pressure damaging them? Also I've always ran Bosch plugs never any issues. I installed NGK. It runs like a plug is breaking down. Has anyone had any issues with NGK? Thanks for advise
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Mrunyan2001
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PostPosted: Wed May 12, 2021 6:10 pm    Post subject: Re: Missing? Reply with quote

NGK BR6HS is what I installed. I read a forum that these might be too cold causing fouling. Resistance on NGK 4.89 ohms. I pulled a spark plug out of old engine Bosch super 491 no resistor .001. I found champion 306 no resistor through my shop. Should take care of fouling. Sometimes over thinking like I do gets you on wrong track
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YDBD
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PostPosted: Wed May 12, 2021 8:38 pm    Post subject: Re: Missing? Reply with quote

Once it's hot it runs fine?

Vacuum leak is a possibility.
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L5wolvesf
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PostPosted: Thu May 13, 2021 10:47 am    Post subject: Re: Missing? Reply with quote

Mrunyan2001 wrote:
I dropped pressure to 2psi resync them. I noticed from factory the accelerator pump on left carb was adjusted more about 3mm more. I turned it out to allow it to move about 5mm like the other side. Running pretty bad now. I've run buggies my whole life. My first dual carb. Very aggrevating .. The top gaskets do seem a little wet. Are you saying I need to replace needle seat and top gasket due to over 4 psi fuel pressure damaging them? Also I've always ran Bosch plugs never any issues. I installed NGK. It runs like a plug is breaking down. Has anyone had any issues with NGK? Thanks for advise


Any carb(s) I do not know the history of, or are dirty, are not tuned, etc I inspect, document and rebuild. It doesn't take a lot of time or money - especially compared to chasing problems 1 symptom at a time. Rebuild kits usually include needle / seat, gaskets, jets (useful in case your current jets have been drilled to an unknown size).

Until the carbs are up to snuff I would not wonder about the plugs heat range. Your engine doesn't sound like it is modified all that much from what you wrote. Also, new stock plugs give you a baseline to work from. A different plug is another question to try to figure out on top of the unanswered ones.
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Mrunyan2001
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PostPosted: Thu May 13, 2021 12:16 pm    Post subject: Re: Missing? Reply with quote

These are brand new carbs maybe 50 miles. New filters etc. Clean fuel. I am gonna try these new plugs. If no go I'm gonna tear into carbs you never know something from factory could have gotten there. eliminate that and go forth. Thanks
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Daddy o's 67
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PostPosted: Fri May 14, 2021 8:17 pm    Post subject: Re: Missing? Reply with quote

Kaddie Shack has a good write up on tuning Kadron Carbs.
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