Carburators at altitude

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Momboy007
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Joined: Fri Apr 01, 2016 6:56 pm

Re: Carburators at altitude

Post by Momboy007 »

Hello Again Maniac,

I would bet that the jets have been changed as I just bought the buggy from Nate at Turnkey Manx. I do not know what kind of exhaust I have, but I believe it is from Meyers Manx, it is a header though.
Do I need to do anything with the timing and other jets? (Idle, air, or pilot)

Thanks,

Rick
ManxManiac
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Re: Carburators at altitude

Post by ManxManiac »

As I posted before... make sure the spark plugs are clean, not sooty! I highly recommend installing new Bosch W8AC & gap them @ .045"! NGKs work well too, I sometimes use B5HS. Check to make sure the timing is set at... 30* @ 3000 rpms! If you check the main gas jet, a #130 should work fine since your engine has a header! The carb probably needs to be adjusted correctly too, which can be found in most VW repair manuals or on the instruction sheet of a carb kit.
The 34 pict carb/009 dist. combo, usually has a "flatspot" just off idle & there are some ways to get rid of it... "google" 34 pict 009 distributor flatspot" & several places should come up with minor mods you can make to get rid of it!!!
IMO... you are better off getting rid of the 009 dizzy & running a SVDA distributor (Single Vacuum Dual Advance) as it will get rid of the flatspot w/o carb mods! The SVDA dizzy has a "single vacuum advance" pot on it! It also has "mechanical advance", so between the vacuum & mechanical, it will meet the timing needs of your engine much more efficiently, increasing driveability & fuel mileage! Well worth installing!
Michael Cates
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Ventura, CA
Original Meyers Manx "Xena"
M1609C8S22
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Re: Carburators at altitude

Post by 1856 »

What Bill said...
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5150bossman
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Re: Carburators at altitude

Post by 5150bossman »

Obviously, like anything dune buggy, there is more than one school of thought. All I know is with our buggy (1776 with Weber 40), I wasn't happy with the performance at altitude running a sea level set up (or lack there of, choking, smoking and running rough). Once re-jetted, it runs nice and smooth (sans a little power). I haven't tried the timing advance yet.
ManxManiac
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Re: Carburators at altitude

Post by ManxManiac »

What Bill Schuster posted!!! LOL Just keep the rpms up & drive it like you stole it!!! You'll be OK!!! LOL BTW... that's the way I drive, just ask the guys I've run with!!! LOL
Last edited by ManxManiac on Tue Jun 28, 2016 5:56 am, edited 1 time in total.
Michael Cates
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Ventura, CA
Original Meyers Manx "Xena"
M1609C8S22
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jsturtlebuggy
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Re: Carburators at altitude

Post by jsturtlebuggy »

If you are running that rich at Big Bear, more than likely you are running too rich where you live. To compensate with hesitation from the carb and combo one thing that most will do is run a larger idle jet.
I spend countless hours on my own projects and others vehicles trying to fix the problem. They never really get rid all of the hesitation. Even with a proper distributor you can still have a hesitation The 009 has to be advanced at idle to much to get proper total advance. Somewhere between 0 to 5 degrees BTDC is all you want timing to be at idle. And around 30degrees total advance. The accelerator pump nozzle has to be aimed right at the opening between the throttle plate and side of carb. And it has to have the proper amount of fuel squirting out of it. The linkage is adjustable to do this.
The idle jet is suppose to be a .55mm which is a little lean with the a aftermarket exhaust system that has less back pressure than stock at close to sea level altitude. A .57 to .60mm idle jet usually works better. A .55mm should work for Big Bear. It a simple jet to change on the outside on the right side. Just needs a screw driver.
I have plug gauges I use to check jet sizes. There not something everyone has. I would remove the idle jet and look at it. It about the size of the smallest you would find on a torch tip cleaning tool. You could also take the jet to Paradise Motorsports in San Marcos or B&R repair and parts in Oceanside to have it checked and maybe pick up a couple of different sizes to try.
The idle jet circuit is used up to around the 3,000 RPM range transitioning to the main jet circuit.

Now it the engine has a different then stock camshaft, then no matter what you do, it will be very hard to try and get it to run correctly with the carb you have.

4265
Joseph
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Having fun with Buggies since 1970
Worked in VWs in shops since 1970
Harry
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Re: Carburators at altitude

Post by Harry »

Hi everyone,
Thanks for all the great info. They really help and starting to make some sense.
It seems like I may having the same type of problems which include altitude, running rough, motor dying at idle and poor gas mileage and fuel outside of carb. Kind of the same issues Rick (Momboy007) having.
Driving was fine from Valley Center to about 3/4's way to San Francisco Bay Area. Then, I notice I was burning through a lot a gas with poor gas mileage. In 20 miles, I went through half a tan of gas.

I was driving the buggy like I stole it but I don't think it would cause the above issues.

I then saw a you tube video "HOW TO FIX FUEL CARB PRESSURE PUMP PROBLEM VW MANX DUNE BUGGY CARBURETOR SOLEX WEBER" by Milo Manx where he suggested adding a fuel pressure regulator to the carb. https://youtu.be/vRYOW9WLHLs

Any thoughts on that? Would this work to fix any of the above issues? Or is there a more "maintenance free carb" or more "efficient carb" for VW's?

Thanks for the help.
H
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jsturtlebuggy
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Re: Carburators at altitude

Post by jsturtlebuggy »

Harry,
I would first check the fuel pressure from the pump to the carb. Should be in the 3-4lb range. If it is above that, yes install good quality fuel pressure regulator. I use the Holley 1-4 regulator on some of my projects.
With using that much fuel, I would be checking to see if float has started to sink. Floats can get holes in them allowing it to fill with fuel. Also check to see if inlet valve is loose and if main jet has come loose.

You can find a reasonable price fuel pressure gauge for checking pressure at Harbor Freight and other automotive parts stores. You tee it into the line from pump to carb and run the engine to check the pressure.
Joseph
Manx Club #1095
Having fun with Buggies since 1970
Worked in VWs in shops since 1970
ManxManiac
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Re: Carburators at altitude

Post by ManxManiac »

BTW... when I installed my dual Kadron 40mm carbs on Xena's engine, I was told to keep the fuel pressure "under" 4 psi!!! I checked it & it was almost 5 psi!!! So I checked out all of the different fuel pressure regulators & someone reminded me about putting several fuel pump gaskets together to raise the pump on its mount, thereby effectively shortening the throw of the pump arm & reducing pressure a bit!!! If I remember correctly, I used 4 gaskets & after I got it back together & measured the pressure, it was only 3 1/2 psi!!! That's been a little over 10 years ago & it is still working great!!!
Michael Cates
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Ventura, CA
Original Meyers Manx "Xena"
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jsturtlebuggy
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Re: Carburators at altitude

Post by jsturtlebuggy »

Stacking gaskets and shortening the fuel pump both reduce the volume the fuel pump puts out.
Joseph
Manx Club #1095
Having fun with Buggies since 1970
Worked in VWs in shops since 1970
ManxManiac
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Location: Ventura, CA

Re: Carburators at altitude

Post by ManxManiac »

Not only did it work on Xena all these years, I know of a couple dozen VW fuel pumps it has worked on!!! Of course it reduces not only pressure, but volume too, but it is a minuscule amount, which is usually just enough!!!
Michael Cates
ManxManiac
#958
Ventura, CA
Original Meyers Manx "Xena"
M1609C8S22
Momboy007
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Re: Carburators at altitude

Post by Momboy007 »

Hello All,
Well, I put the little buggy in the shop after buying the recommended jets, and the VW Mechanic said my carburetor was the problem, the idle air cutoff was not working and the carburetor was all rusted up so badly he said it is not even worth it to rebuild, so I am putting a new carb on it and he said he will dial it in for me.
I will let you know how things went when I pick it up later this Week.

Rick
Momboy007
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Joined: Fri Apr 01, 2016 6:56 pm

Re: Carburators at altitude

Post by Momboy007 »

Hello All,
Well I finally got the buggy back from the shop and I was given a rebuilt carburetor and it runs so so much better now, he also did a little rewiring and it runs so good now I can't begin to explain, it pulls from idle to around 4 K

I am now happy, except for my shifter, which I will put in another post

Rick
Harry
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Joined: Fri Jan 15, 2016 6:32 am

Re: Carburators at altitude

Post by Harry »

Hello,
Thanks for all the tips that came in. I did a lot of reading and research.
It turned out that the constant dying of the motor, rough idle and excess fuel consumption was linked to a bad electrical connector to the fuel idle shut off solenoid. (Noticed it was making a clicking contact noise when the ignition was on and killing the motor when wire was touched and vibrated at idle).

The connection was replaced, fuel air mixture adjusted, and choke cleaned and adjusted.

Now it runs great.
Thanks.
Harry
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