MK1

How to Adjust a Carburetor

Adjusting the Air and Fuel Mixture

1

Locate the air filter and remove it. On most cars, you'll need to remove the air filter to expose to carburetor and adjust it. Open the hood and make sure the engine is off before locating the air filter and removing the assembly. Unscrew the wing-nut and any other connectors, and then remove the air filter entirely.

• Depending on your make and model, and the kind of engine in the vehicle, the air filter could be in any number of different places on the engine. Consult the owner's manual or the shop guide for your vehicle.
• On most carbureted cars, the air cleaner housing is attached directly to the carburetor.

2

Find the adjustment screws on the front of the carburetor. There should be two screws on the front of the carburetor, which are used to adjust the air and fuel mixture.

Often these look like flat-head screws and you can use a screwdriver to turn them, adjusting the amount of fuel and air mixing in the carb.

• Some carburetors, such as the Quadrajet found in most GM vehicles, have a special screw and require a specific adjusting tool. The Quadrajet uses a Double "D" carburetor adjusting tool.
• Other carburetors may have a 4 corner idle mix adjustment (4 idle mixture screws).

3

Start the engine and let it warm to normal operating temperature. Check the temperature gauge to know when it's at the appropriate running temp, and listen to the sound of the engine to get some sense of the adjustments that need to be made.

• An engine that runs lean will ping at higher RPM, when the throttle is open, as if you were flooding a gear. More gas needs added to the mixture.
• An engine that runs rich won't necessarily make a change in sound, but you'll be able to smell it. Bring the gas down some.[1] An engine that runs too rich at idle will cause the plugs to be fuel-fouled, leading to a vehicle that is harder to start cold.

Adjust both screws equally and find the right mixture. Adjusting the carburetor is a lot like tuning a guitar or other stringed instrument. You want to turn the screws equally, smoothly, and slowly until you find the sweet spot. Regardless of whether or not the engine is running too rich or too lean, bring it down to a very lean mixture by turning both screws a quarter-turn at a time, counter-clockwise, then slowly bringing them back up to an equal and smooth mixture.

• Adjusting the mixture is an imprecise art, requiring that you know your engine well and listen close. Bring both screws up slowly and listen until the engine purrs smoothly. Any raggedness or rattling is a sign of too lean a mixture. Keep turning until you find the sweet spot.
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5

Replace the air filter assembly. When you've got the carb adjusted, put the air filter back on and you're ready to roll.

If you need to adjust the idle speed as well, wait to put the air filter back on until you're finished.[2]

Tips

• If your car is equipped with a tachometer, you can use this as a tool to adjust idling speed (revolutions per minute or RPMs). Check your owner's manual for the correct RPMs.
• Tightening the idle adjustment screw increases idling speed while loosening the screw decreases idling speed.
• If after adjusting the idle mechanism, the engine does not run smoothly, go back to making air and fuel adjustments and repeat the steps for both air and fuel and idling adjustments.
• There is a difference in idle speed with the car in neutral/park versus in gear for an automatic car. Do not adjust idle speed with the car in gear unless there is someone in the driver's seat with their foot on the brake.
• There are some cars that have multiple carburetors, i.e. European and Datsun, that must also be balanced for air flow before adjusting.

Warnings

• Remember that when you are working on a carburetor, you are working with a fuel source. Take all necessary precautions for working around gasoline.
• Keep in mind you are also working on a running motor. You can seriously injure yourself or damage your engine if you are not careful. Work slowly and thoughtfully and make sure your clothes don't have any hanging strings or cords that could catch in the engine.

Timing Discussion

The following topics are discussed in this article -

Why Timing?
Distributor and Timing
Timing and Cooling
"Run, Stop, Adjust"

Why Timing?

Timing is required to make the spark jump across the spark plug at the proper intensity, duration and at the strategic time to properly "burn" (not detonate) all the fuel, to assure that the burning is:

Complete - to reduce exhaust emissions.

Powerful - to get the most power to the rear wheels.

Efficient - for economy and cooling, to prevent the engine "burning up".

Distributor and Timing

If the best timing for power coincided with the same timing for minimum emission, or if the engine were going to run at some constant rpm, the timing problem would be simple. However, the distributor (timing device) must be able to apply the spark at the right time and for the right duration throughout the entire rpm range.

• The fuel-air mixture is compressed by the piston being pushed through the cylinder toward the head. This compression makes a hot, explosive mixture which must burn, not explode (detonate or "ping").
• With detonation comes excessive heat, a hard hammer thrust to the piston top and damage to the head and the rest of the engine.
• Detonation can happen if the spark plug fires too soon (i.e. The timing is too advanced - Pre-ignition) or if there is an additional ignition source within the combustion chamber.
• There is one best time to strike the match (timing) and one best length of time for the match to burn.
• If the spark plug fires too soon, the mixture pre-ignites or detonates.
• If the spark plug fires too late, the mixture doesn't all burn.

in other words, the length of time the match is lit is constant throughout the rpm range. Remember - Top Dead Centre (TDC) is the point where the piston stops dead still, changing its direction from travelling towards the cylinder head back toward the crankshaft. At idle, the one best time for the spark plug to fire is somewhere around TDC or a little before, However, as the rpm increase, the timing must be advanced (the match lit sooner), in order that all the mixture can be burned in the relatively less time allowed. This means that the burning now starts before the piston reaches TDC and continues on past TDC. At 3600 rpm this is happening 1800 times a minute in each cylinder. If the match is not light faster (sooner), the mixture has no time to burn properly.

As the engine's rpm increase, the spark is advanced degree by degree to about 20° Before Top Dead Centre (BTDC) somewhere around 2500 rpm. The relationship between the degrees of timing advance and rpm can be plotted on a graph, the resulting curve is called an Advance Curve.

Due to the different spark timing requirements under certain engine conditions (of varying speed or load) the distributor has an automatic advance device (advancing the spark means that it comes earlier in relation to the piston position). The spark timing is altered by two methods.

• Centrifugal force - Engine speed governs the centrifugal advance.
• Vacuum Force - Throttle opening governs vacuum advance.
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Timing and Cooling

The Volkswagen and most air-cooled cars have very tight valve trains and water cooled engines have notoriously sloppy ones. This is one reason why water-cooled engines are timed in an rpm range where the spark timing is advanced and air cooled cars are timed either statically or at idle when the timing is retarded.

If an air-cooled engine's timing is too advanced it will overheat and run too hot.

~~~

"Run, Stop, Adjust" Method

Someone wrote to ask -

My setup: Beetle 1971 (pre-August) 1600cc single port Engine, 009 distributor and Brosol H30/31 carburetor. My question has to do with timing. It says in the BugMe video series that timing with a 009 should be set at 7.5 degrees BTDC. However from another source in a popular Beetle forum maintains it should be at 5 degrees ATDC for my particular setup. I followed the 7.5 degree BTDC setting and didn't find the running too good.

I then took the car on a run and every now and then stopped to turn the dizzy just a bit one way and then the other way to find the "sweet spot." I got it positioned at a fairly okay position and also with the most minimum (hardly any) of 'gurgling' pre-ignition type sound when suddenly pushing down the pedal going uphill.

Could you please tell me what actually is my correct timing mark? I have been to your Website to look but was not able to locate the specific information I need.

Would you consider my "run, stop, adjust distributor' method described above an acceptable way to set the correct timing?

Rob responded -

With a 009 distributor the correct setting is 28-32 degrees total advance at 3000+rpm. That usually comes to about 7.5 degrees BTDC (which the BugMe video mentions) at idle -- but not always. Since the 009 distributors vary in build quality and the total advance is more important than the idle setting -- the idle setting could be anywhere from about 5 to 10 degrees BTDC after setting the total advance. Once you know what THAT idle setting is for THAT 009, you can set it static in future if you wish.

If you can identify the TDC mark on the pulley, 30 degrees is 46.5mm to the right of that around the rim, so 28-32 is 3mm either side of that. If you aren't sure about the marks, describe them to me and I might be able to help. VW used at least four different sets of pulley marks over the years.

Use as much of the 28-32 degrees BTDC as you can without the engine detonating/pinging, as this helps reduce any acceleration stumbles a little (caused by the 009 distributor -- you will find that discussed on our Web site. See our article on Timing the 009 Distributor).

If the engine still detonates at 28 degrees BTDC maximum advance, try using a higher octane fuel. Never use less than 28 degrees BTDC maximum advance, as the 009 distributor produces a slight underadvance at higher speeds anyway (vacuum distibutors will allow up to 40 degrees under cruising/part throttle conditions for better fuel economy).

Your description of a gurgling/pre-ignition sound is worrisome. That sounds like detonation - I describe it as a harsh uneven clicking sound from the engine when you use heavy throttle at lowish engine rpm. If it's happening in normal driving you probably need to use a higher octane fuel. The VW engine doesn't need a really high octane number, but the later Bugs (1500/1600cc engines) do have a slightly higher compression ratio than the early 1200/1300s and like at least 91 RON octane (about 87AKI in the USA). Using a higher than needed octane fuel doesn't give you more power and won't damage an engine, but using a too-low octane number WILL eventually damage your engine.

The 5 degree ADTC setting some others have described to you is for the 1971-1973 1600 twin port engine (AD, AE series engine numbers) with the DOUBLE vacuum distributor (two vacuum lines to the carburetor). NEVER use this setting with the 009 distributor or any single vacuum distributor or the car will be badly underadvanced at higher rpms, which will result in overheating and poor economy. For your information, the double vacuum distibutor pulled in 5 degrees ATDC at idle as an emissions thing - when you crack the throttle open the retard drops out and the timing jumps to a normal 7.5BTDC and starts to advance from there. The double vac distributor was used for only three model years, then VW used the single vacuum double advance (SVDA) distributor - from the '74 year onwards. It's like a high quality 009 (up to 32 degrees) with added vacuum advance (an additional 8 degrees when needed) - the best of both worlds.

Note: The SVDA distributor is essentially a centrifugal-advance (009) distributor with a vacuum advance assist to help prevent hesitation in all of those stop-n-go situations in city traffic. The mechanical advance takes over out on the highway in the rpm range of 2000-2500+ (highway speeds in 3rd and 4th gear). At the higher rpm the vacuum signal drops and the mechanical advance is (or should be) "all in". The vacuum only pulls in/advances the timing plate right off idle and through the lower range (not neccesarily in the driveway but under load it does). Once the higher rpms are reached, the vacum advance drops off and the mechanical advance takes over.

Also check the jetting in your carburetor. The H30/31 carburetor is often delivered with lean jetting as an emissions thing (I've seen main jets as small as 112.5). You should have a 55 idle, 127.5 main and about 125 or 130 air correction jet. (If you had a vacuum distributor the main jet in the carburetor should be a 125, but the 009 distributor needs a slightly richer mixture). The brass idle jet is in the right side of the carburetor, and there is another one there too - the power jet which is normally a 65 (this only provides fuel at high speed high throttle). The main jet is in the bottom of the float bowl. The air correction is a vertical brass screw head with a hole in it between the float bowl and the main throat - you have to remove the carburetor top to see it. Be careful removing this - it's about an inch long as it has a thin emulsion tube (mixes air and fuel before it enters the main throat) attached to it.

If your fuel has MTBE or other oxygenates in it, these will cause the engine to run lean which will worsen any detonation/pinging. This can be corrected by going up in jet sizes -- try 130 for the main jet and just possibly a 60 for the idle. MBTE and other oxygenates enhance the octane number but have less "fuel" in the fuel, so you need to richen the mixture a little to get it back in balance (modern cars have engine computers which do this on the run, but our old carburetted cars have to be manually set with different jets to cope with oxygenated fuels).

Always set the accelerator pump to give a good squirt - this reduces any acceleration stumbles caused by the 009 (single-vacuum distributors ARE better). With the air cleaner off, look down the throat and give the throttle arm a firm tug (the accelerator pump does NOT work with slow throttle movements). You should see a nice long squirt of fuel straight down the carburetor throat past the opening throttle plate, not splashing on anything on the way. If it splashes, twist the delivery tube a little - gently please. There should be an adjusting "bell" with an elongated hole and lock nut in the accelerator pump linkage (right side of carburetor) to adjust the squirt. (See our article on Accelerator Pump Adjustment for more information.)

The "run, stop, adjust" method is not very good at setting the car up properly.

Read our article on Basic Tuneup, and Adjustment of the Solex 34 PICT/3 Carburetor for a complete tune-up guide for your set-up (the 34 and H30/31 series carburetor use similar set-up techniques).

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THE MK2/MK3 gear shift linkage repair guide

VW Jetta MKII Manual Shift Repair Video...

Click the above link to view a good video i found on how to re do a MK2 gear links and bushes

Complete Guide below....


Are you trying to do it with the exhaust and tunnel heatshield still on the car? Ive only done it with the box out when I was changing everything out shifter wise. 

If you're at this point..

You might be able to try to fit one of those mini prybars fit it under the lip of the cup from the cup and pry it upward.

GSF sell the linkage repair kit in the UK:
71709C GEAR LINKAGE REPAIR KIT £5.75 + VAT
I'm not sure where to get this in the US, someone let me know [IMG]http://**********************/smile/emthup.gif[/IMG]
This is what you'll receive:

1x big red bush (in the large bracket that holds the gearlever shaft)
4x hard plastic bushes (only 2 needed, for bracket bolted to the gearbox)
2x big clear soft rubbery bushes (for the relay shaft)
2x small white soft rubbery bushes (for the ends of the shift rod)
2x rivets (un-needed, used for the red bush housing but no need to drill out old ones)
4x soft foamy washers (used on the short & long link rod ball joints)
Its also worth buying an uprated relay shaft bush from:
http://www.4crawler.com/Diesel...shtml
Will improve the forward back feel a great deal 
Ok pop the bonnet and this is what you'll see, note I've already fitted the weighted shift rod:

Remove the header tank and place it out of the way, this gives you loads of room to work in. Pre 90 spec ones are just slotted into the bracket, 90 spec ones are held on with 2 bolts/studs under the black plastic trim bit. Don't forget to disconnect the level sensor if one is fitted!
The short & long rods with the plastic end caps have little clips to clamp the ends, carefully unclip these, I snapped one off and had to make an emergency visit to the scrappy! Both rods should then pop off with a little persuasion.
Lever the spring clips out of the metal shift rod and remove, make sure these don't ping off & disappear!
Undo the 13mm nut on top of the relay shaft, and remove the large metal arm.
Loosen the 13mm pinch nut & bolt on the clamp on the gearlever shaft bracket, until it can be removed (you might want to mark its position but Chances are the alignment will be out after refitting all the bushes anyway!)
Remove the 3 13mm bolts holding the relay shaft bracket to the steering rack, and remove. This is tricky, you have to wiggle the bracket about whilst holding the gearlever shaft as far back as it will go, there is only just enough clearance!
Your engine bay will now look like this (note 2 of the gearbox linkage bracket bolts are circled):

Now you have 2 choices, either remove the bracket bolted to the gearbox, or just unbolt the lever from the bracket. If you wish to change the gearbox it would be a good plan to do it at the same time as the only way to do it is to remove the linkage bracket. It also makes it easier to fit the replacement bushes and refit the lever, plus you can clean it up nice :smiley:
To remove the bracket:
Undo the large bolt through the middle of the gearbox mount.
Jack the gearbox up as far as possible, go slowly as the clutch arm will hit the inner wing.
Remove the bolts holding the linkage to the gearbox and it should slide out nicely
If you want to replace the gearbox mount, there are 2 smaller bolts holding the gearbox mount in the subframe, remove these and you'll have JUST enough clearance to remove it and swap in the new one.
To remove the lever from the bracket:
Simply remove the 13mm nut & bolt and the lever will slide off :smiley:
Ok now you'll have a pile of linkage bits on your workbench, after cleaning em up with a wire brush you'll have something like this:

(notice I forgot to put the small plastic linkage and the lever mentioned above in the pic)
It should now be pretty obvious which bushes go where, if you are unsure I've listed the locations above. The tricky one is the big red bush but it is possible to rip the old one out and fit the replacement without drilling out the rivets, put it in a tub of warm water first to make it a wee bit more flexible. Then as the red book says, re-assembly is the reverse of removal, make sure you grease up the moving parts while you put it all back together :smiley:
Now to set up the alignment, dave2227 sells the alignment tool on ebay to make the job easy:

Also heres a link to an engineers diagram of the tool, so you can get it made yourself:
http://vwtech.no-ip.info/image...5.png
But being a tight Northerner I just used an old cassette tape held in the gap between the reverse gate & lockout lever with duck tape! Make sure you do the pinch bolt up tight, I made the mistake (twice!!) of not doing it up enough and lost all my gears a day or so afterwards as a result :grin:
Job done:

u can find a rebuild kit here in the states at techtonictuning .com.

GOLF 7R VS RS3!!!!! CLICK TO SEE THE FULL VIDEO

GOLF 7R VS RS3!!!!!

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