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videoguy009 Samba Member
Joined: March 31, 2008 Posts: 711 Location: Saint John N.B. Canada
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Posted: Sun Mar 01, 2015 1:02 pm Post subject: Idle mixture screws |
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Found an issue with the popping carb on my dual 40 idf carbs.the idle mixture screws have no effect when turning them.If I turn them in all the way the carb stays running strong.I have checked for vacuum leaks and there are none.I can get a good idle and a good sync but when I try to adjust the mixture screws to richen it up to take the popping out they do nothing.The linkage is right on as I followed the correct procedure,unhook for syncing and reattach and listen for change in idle.No change.I am running 55 idles and 135 mains. _________________ 1971 Super Beetle |
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leaker Samba Member
Joined: May 18, 2009 Posts: 348 Location: richmond,va
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Posted: Sun Mar 01, 2015 4:04 pm Post subject: |
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Could be plugged idle jets, idf's plugging up is common, although I have never had all four plug up at the same time. |
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MURZI Samba Member
Joined: August 25, 2005 Posts: 5063 Location: Madisonville, La
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Posted: Sun Mar 01, 2015 4:42 pm Post subject: |
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Before you adjust the mixture screws make sure that the throttle stops are not screwed into far. If you expose the progression ports in the carburetor by having the throttle blades in the wrong position the carb will run rich....
Disconnect your linkage at each carb, set the idle mixture screws at 1.5 turns from seat. now start the car and adjust "snail" to about 4 or 5....the engine will be idling super slow. Now adjust your mixture screws. _________________ 62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam |
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Casting Timmy Samba Member
Joined: August 04, 2012 Posts: 1221 Location: Kansas City, Kansas
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Posted: Sun Mar 01, 2015 4:48 pm Post subject: |
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The fuel has to be coming from somewhere if the screws don't affect idle.
Do Murzi's suggestion as most likely it's comingfrom the progressive circuit as the throttle shafts are too far open. YOu can also use a vacuum gage to adjust your throttle plates if you have a distributor vacuum advance port on your carbs. Simple adjust the plates until you see vacuum and then unscrew until the vacuum goes away.
You can also check fuel pressure to make sure it's not over 3.5 psi and pushing the fuel thru the carbs.
Are these carbs new to you? Checking float height would be my third even if the carbs were new. |
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videoguy009 Samba Member
Joined: March 31, 2008 Posts: 711 Location: Saint John N.B. Canada
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Posted: Sun Mar 01, 2015 5:04 pm Post subject: |
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I am running a mechanical dist.The carb is 3 yrs old and the other is new which runs like a charm.They are new jets in them but i know that doesn't mean there isn't a blockage somewhere in the idle circuit.One thing I did notice today is when the car was running the exhaust from that side would go hot then cold intermittently.I guess that would mean plugged idle circuits?Sorry,never thought to mention that! _________________ 1971 Super Beetle |
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Casting Timmy Samba Member
Joined: August 04, 2012 Posts: 1221 Location: Kansas City, Kansas
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Posted: Sun Mar 01, 2015 8:21 pm Post subject: |
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I don't see it as a blocked idle jet. The progressive circuit feeds off the idle jet as well as the idle screw.
On the exhaust, was that during the same throttle setting or what else was happening then? |
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videoguy009 Samba Member
Joined: March 31, 2008 Posts: 711 Location: Saint John N.B. Canada
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Posted: Sun Mar 01, 2015 8:30 pm Post subject: |
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It was on the same throttle setting.When I used this carb as a centermount one jet was plugged and I noticed the heat riser was cool.I pulled the jet and their was debris on it.This is what makes me think one or two jets are plugged as the exhaust runs cool.When I rev the car for the mains to kick in their is no problem as it runs strong.I have not been able to get back to the car today to check things. _________________ 1971 Super Beetle |
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MURZI Samba Member
Joined: August 25, 2005 Posts: 5063 Location: Madisonville, La
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Posted: Sun Mar 01, 2015 8:59 pm Post subject: |
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videoguy009 wrote: |
It was on the same throttle setting.When I used this carb as a centermount one jet was plugged and I noticed the heat riser was cool.I pulled the jet and their was debris on it.This is what makes me think one or two jets are plugged as the exhaust runs cool.When I rev the car for the mains to kick in their is no problem as it runs strong.I have not been able to get back to the car today to check things. |
There is your problem....using a center mount as in dual carb application. My bet is your emulsion tubes are different and the throttle plates have holes drilled in them. (hence the no response from idle mix screws) _________________ 62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam |
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videoguy009 Samba Member
Joined: March 31, 2008 Posts: 711 Location: Saint John N.B. Canada
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Posted: Mon Mar 02, 2015 5:37 am Post subject: |
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The butterflies on the single carbs do have holes drilled in them from the factory.Could this be my big issue. _________________ 1971 Super Beetle |
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MURZI Samba Member
Joined: August 25, 2005 Posts: 5063 Location: Madisonville, La
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Posted: Mon Mar 02, 2015 6:27 am Post subject: |
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Yes. also check emulsion tubes. You need f11's. _________________ 62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam |
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videoguy009 Samba Member
Joined: March 31, 2008 Posts: 711 Location: Saint John N.B. Canada
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Posted: Mon Mar 02, 2015 7:40 am Post subject: |
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Do the emulsion tubes hold the main jets.Is that them? _________________ 1971 Super Beetle |
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MURZI Samba Member
Joined: August 25, 2005 Posts: 5063 Location: Madisonville, La
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Posted: Mon Mar 02, 2015 8:17 am Post subject: |
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Yep _________________ 62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam |
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videoguy009 Samba Member
Joined: March 31, 2008 Posts: 711 Location: Saint John N.B. Canada
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Posted: Mon Mar 02, 2015 8:19 am Post subject: |
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With the holes drilled in the butterflies,does this cause the carb to bypass the idles curcuits or something similar to that. _________________ 1971 Super Beetle |
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MURZI Samba Member
Joined: August 25, 2005 Posts: 5063 Location: Madisonville, La
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Posted: Mon Mar 02, 2015 8:21 am Post subject: |
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Yeah. Like a vacuum leak. Put a piece of tape over the holes... Temporary... Youll see a difference right away. _________________ 62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam |
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videoguy009 Samba Member
Joined: March 31, 2008 Posts: 711 Location: Saint John N.B. Canada
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Posted: Mon Mar 02, 2015 8:25 am Post subject: |
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Thanks for everything.I have been chasing a dead horse for the past week.I will have to purchase an identical carb to the one I bought and everything should go well.Thought I could save money by using my old carb,but guess what.Lol. _________________ 1971 Super Beetle |
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MURZI Samba Member
Joined: August 25, 2005 Posts: 5063 Location: Madisonville, La
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Posted: Mon Mar 02, 2015 8:32 am Post subject: |
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Just loctite some small screws and nuts in the holes. No biggie. Emulsion tubes can be bought too. F11 is what you need. _________________ 62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam |
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Back to top |
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videoguy009 Samba Member
Joined: March 31, 2008 Posts: 711 Location: Saint John N.B. Canada
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Posted: Mon Mar 02, 2015 8:40 am Post subject: |
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Will do and save some money.Thanks for the advice. _________________ 1971 Super Beetle |
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