Autolite 2100 Carburetor Rebuild

Click on the pictures to enlarge them.

Overview: Gasoline and air travel through many small passageways inside the carburetor.  Over time these passageways may become blocked with dirt or residue from evaporated gas if the car has been sitting for an extended period.  The result is poor operation and and decreased gas mileage.  Rebuilding the carb entails taking the it apart, soaking it in carb cleaner, blowing out all of the passages with compressed air, reassembly, installation and adjustments.  A few small parts are also replaced during reassembly along with all of the gaskets.

Step 1- Remove The Carburetor From Your Car - Estimated Time 45 Minutes. 

Hint - You can use the pictures here during installation if you forget how things go back together.

• Disconnect the PCV hose running from the base plate in the back of the carburetor to the PCV valve connected to the passenger side valve cover.
• Disconnect the cold choke tube running near the top of the carb, passenger side, to the exhaust manifold.

• Disconnect the vacuum line running from the passenger side of the carb to the vacuum advance on the distributor.
• Disconnect the gas line, front passenger side, running to the fuel filter.
• Disconnect the throttle return spring, driver's side
• Unclip the throttle from the carburetor.
• Remove the 4 nuts securing the carburetor to the manifold at the base of the carb.

You should now be able to remove the carburetor from the car.  It should lift straight off.

Things to look for:  When you remove the carburetor and there is oil pooling up on the manifold under where the carb sat your PCV valve may be bad.  It gets there through the PCV valve from the passenger side valve cover.  Normally the valve is supposed to allow the crank case gasses to go by but not oil. 

Step 2 - Dismantle The Carburetor - Estimated Time 1 Hour 15 Minutes.

• I start by removing the choke components first.  It's a good place to start because the choke plate pull down rod prevents the top of the carburetor from coming off easily anyway.  A good percentage of the parts are part of the choke.

• The top can then come off.  It's held on by 4 screws and the bolt for the air cleaner.

• Next I remove the carb internals starting with the fuel bowl in the front.  The rod that holds the float is secured by the wire clip that runs behind the needle seat.  Use a pair of long nose pliers to remove the wire clip and the rod with the float can then be removed.
• Remove the float needle and its seat.

• You can now see the jets at the bottom of the fuel bowl.  They are round and slotted.  You can remove them with a flat bladed screwdriver but BE CAREFUL.  They're made of brass and the slotted portions strip easily.  I have found that these are sometimes stuck so use the biggest screwdriver you can find to maximize torque and minimize the chances of the blade slipping from the slot.
• The fuel bowl is now done so move to the back of the carburetor and remove the screw that hold the venturis in place.  Take off the plate on top of the venturis (air distribution plate) if there is one.  Hold onto the venturis and turn the carb upside own.  A small rod and ball bearing will come out of the hole where the screw was.  Now take out the venturi cluster.  The inside of the carb is done.

NOTE - I don't remove the throttle plates, which open and close with the throttle, for two reasons: 1)  You have to be careful when you put them back on such that they are fully open with wide open throttle and fully closed at idle and 2) if they're not put on tight enough there is a chance you can damage your engine if the screws come loose and work their way into your engine.  I do make sure the plates are open when I soak the carburetor to ensure the cleaner works into the passages near where the plates sit when they're closed.

• You can then start dismantling the outside of the carb.  On the driver's side remove the idle speed adjustment screw and spring, anti-stall dashpot (on automatic transmission cars) and mounting bracket, then remove the clip that holds the accelerator pump rod to the throttle.  When you remove the accelerator pump rod make sure to note which holes it's connected to if you don't have the proper specifications from the shop manual or carb rebuild kit.

• On the front of the carb remove the 4 screws for the accelerator pump.  Inside the pump there should be a diaphragm type element and a spring.  There is also a rubber plug attached to the base of the carb.  Remove the plug.
• Also in the front are the idle adjustment screws.  Take them out also.  Some people note how many turns it takes to remove them such that they can be put back at the same position when the carburetor is reassembled.  I would do this as a backup measure in case there is difficulty setting the idle mixture per the shop manual method
• The final part of the disassembly is the power valve on the underside of the carb.  Remove the 4 screws that hold on the cover.  You may need a large socket (I forget the size) to remove the power valve but a large pair of pliers should be good enough.

Step 3 - Soaking the Carburetor in Cleaner - Estimated Time 15 minutes (then let it sit over night)

• You need a metal bucket for this part as the cleaner will damage plastic.
• There are plastic pieces in the choke that should be put to the side too.
• Makes sure the throttle plates are open to let the cleaner get into the passageways in the barrels.
• You really only need to soak the main body of the carb, venturi cluster and choke housing but I soak everything because it comes out nice and clean.  The most important thing is to make sure those 3 items are completely submerged in the cleaner.  Arrange the parts such that this happens.  Keep this in mind when looking for a bucket as buckets that are too wide may not result in not enough depth when the carburetor cleaner is poured in.
• Wear rubber gloves when dealing with the carburetor cleaner.  It's nasty stuff.
• The cleaner should be poured outside or in the garage as the fumes are terrible.
• Let the parts sit in the cleaner overnight.

Step 4 - Blowing Out the Air Passageways - Estimated Time 30 Minutes

• Wear rubber gloves here as you'll be picking up parts that were sitting in the cleaner.
• Protective eyewear and something over the mouth are a smart move too.
• Drain off the parts cleaner.
• Rinse the main body with water.  Try to get the the air and gas passageways if possible.
• Blow out the gas and air passageways with compressed air.  If you don't have an air compressor you can get by with the cans of compressed air that are used to clean computer keyboards.  NOTE - You will undoubtedly get some liquid spray on you when blowing out the passageways.  Keep that in mind if you are thinking about not covering your eyes and mouth.
• Rinse the venturi cluster next then blow out the passages.
• Rinse the choke housing and ensure the vacuum passageway connecting to the main body is clear.
• Rinse the remaining parts.  Allow everything to dry.

Step 5 - Reassembly - Estimated Time 1 Hour 30 Minutes

• The carburetor rebuild kit contains some of the smaller parts and all gaskets.  I don't recommend this brand for first timers as it didn't have directions. NOTE - The kits contain extra parts to ensure they can be used for different carburetors. Don't be alarmed if you have extra parts.

• I start on the outside front.  For the accelerator pump the first thing you need to do is insert the little rubber plug (elastometer valve) into the base of the carb.  Use a pair of needle nose pliers to pull the nipple from inside the fuel bowl.
• After that comes the return spring and diaphragm.  The wide end of the spring should touch the base of the carb and the button on the diaphragm should face outward.
• Put the cover over the diaphragm and insert the 4 screws.
• Next insert the idle mixture screws and springs.  The initial idle mixture setting should be 1 1/2 turns out.  Turn the screws in until their lightly seated and then back them off 1 1/2 turns.  NOTE - Don't try to really tighten the screws alot.  Doing so will damage the tip and they'll have to be replaced  Lightly seated means just that - lightly seated.
• That's it for the front so I then go to the to the driver's side.  Insert the accelerator pump rod into the proper hole on the pump arm.  Check the shop manual or instructions that came with the kit to see which is the proper setting.  Attach the other end of the rod to the throttle with the retainer.  Check the documentation for the proper setting for this too.  If no documentation is available then you may try putting it back in the same holes it was in if you think they're correct.
• Next do the idle speed adjusting screw and spring.
• Attach the anti-stall dashpot mounting plate to the base of the carb then screw the anti-stall dashpot into the mounting plate.  Check the specifications for the clearance on the anti-stall dashpot.  The clearance is measured by depressing the plunger on the dashpot with a flat blade screwdriver and taking the measurement between the dashpot and the throttle.  Adjust the position of the dashpot until the proper clearance is obtained.  If you don't adjust this properly then at least be sure to check that the dashpot isn't so off such that it's holding the throttle open.
• Next comes the choke but there's too many small parts for me to go into it in detail.  Here are some pictures of it assembled.  If you can't make things out here then be sure to take your own pictures or take notes.

• Don't put the black circular cover with the spring on just yet as there are some adjustments that need to be made to the choke after the rest of the carb is fully assembled.
• The only remaining thing on the outside of the carburetor that needs to be assembled is the power valve on the underside of the carb.  The rebuild kit should have a new power valve.  There is a gasket that goes between the power valve and the base of the carb.  It's a round gasket but the the inner cut-out section has straight edges on it.  The power valve should be on tight but not gorilla tight.  You don't want to crush the gasket
• Next you can put on the cover over the power valve with a gasket between the base of the carburetor.
• Moving to the inside of the carb we start with the fuel bowl.  Start by putting the main jets at the bottom back in.  They should screw right in.
• Next put the needle seat in.  There should be a gasket between the base of the carb here.
• Put the needle in the needle seat.  The rebuild kit should have a new needle and seat.
• Slide the float over the rod and then attach the wire retainer to the rod.  The wire retainer sits in grooves in the rod.
• Put the rod onto the mounts in the base of the carb and use needle nose pliers to push the retaining wire down the back of the needle seat.  There should be a groove in the needle seat to hold the wire retainer in place.  NOTE - The kit will have an additional small clip that attaches the float tang to the needle.  I put this on but I've seen cases when it wasn't there and everything worked fine.  I suspect some carbs came with it and some didn't but I'm not sure.
• All that's left is to install the venturi cluster.  Start by putting the small metal ball and rod into the hole in the middle.  
• Insert the venturi cluster with gasket next.
• Put the air distribution plate on top of the the venture cluster and then insert the hollow screw over the rod and ball that were inserted earlier.  You may have to shake things a little to get the screw to drop over the rod.
• Attach the choke plate pull down rod from the choke to the top of the carburetor.
• Attach the top of the carburetor with gasket to the base.

Step 6 - Choke Adjustments - Estimated Time 20 Minutes

• There are 2 adjustments that need to be made to the choke for it to work properly.  The first that needs to be set is the choke over-travel lever, which is the screw in the plastic piece behind the main choke housing.
  • Set the fast idle speed screw (under choke housing) such that it comes in contact with the V mark on the fast idle cam.  Make sure it doesn't move from that position.
  • Hold the choke in the rich position.  This can be done by temporarily putting the black spring housing with the spring back on the choke and turning it counterclockwise or by pushing the lever manually inside the choke housing counterclockwise.
  • Place a drill bit (check specs or shop manual for proper size) between the choke plate on top of the carb and the carb base.
  • Adjust the screw such that the coke plate just begins to touch the drill bit.

• Next comes the choke plate pull down adjustment, which is the plastic nut that attaches the choke plate to the choke pull down rod near the top of the carb.

• Partially unbend a paper clip and use a pair of pliers to make a 90 degree bend 1/8 of an inch from the end.
• Put the bent end of the paper clip into the right side of the slot on top of the small piston in the choke housing.
• Push the piston and paper clip down until the paper clip catches on the ridge on the inside of the cylinder.
• At that point push on the lever inside the choke housing counterclockwise.  The paper clip in the ridge should prevent the choke piston from going up.  
• Put a drill bit of the correct diameter (see specs or shop manual for correct size, may be different than last time) between the base of the carburetor and the choke plate.
• Adjust the choke plate pull down such that the choke plate just touches the drill bit.

NOTE Go back and check that the over-travel lever is still adjusted properly after adjusting the pull down.  It should be but mine were so far off that I had to readjust both of them.  You can verify both are adjusted properly if the fast idle screw touches the V mark on the fast idle cam and the proper spacing is between the choke plate and the carb body when the choke is fully closed (lever in choke body fully counterclockwise).

• You can now attach the round, black cover onto the choke.  The end of the spring should slide into the slot on the lever inside the choke housing.  Check the specs to determine the proper orientation.

TIP - You may want to spray the choke internals and externals with WD-40 for prolonged trouble free operation.

Step 7 - Reinstallation On Car - Estimated Time 20 Minutes (Longer if old gasket material is caked on the carb/spacer/manifold)

• The carb should be installed with no silicone "gasket glue" between the intake manifold and the carb spacer and between the carb spacer and the carburetor.  If it was used on prior installations there may be a significant amount of old gasket remaining that must be scraped off before reinstallation.  Try not to let the bits fall inside of the engine.  Gasket remover may be helpful for stubborn portions.
• The carburetor should be installed on the car with a gasket between the carb spacer and the manifold and another between the carburetor and the carb spacer.  Again, don't use any type of adhesive on the gaskets.
• You can then install the 4 nuts onto the mounting bolts coming from the manifold.
• Connect the hose for the PCV valve at the rear of the carb running into the carb spacer.
• Connect the choke tube running from the exhaust manifold to the choke housing.  NOTE - This is difficult to get the tube angled properly to screw onto the choke housing.  The threads on the choke housing strip easily so don't try to force it.  You may want to connect this before bolting the carburetor down as it is easier to get things aligned if the position of the carb can be adjusted.  ANOTHER NOTE - The fuzzy insulation over the choke tube may be asbestos.  Try not to handle it too much.
• On the passenger side of the car install the vacuum line from the distributor.
• In the front of the car connect the fuel line.
• The last thing to do is connect the throttle linkage on the driver's side of the car.  If you can't figure it out there is a pretty good picture of where everything goes near the beginning of this document.

Step 8 - Float Level Adjustment

• To perform this step the fuel bowl must be full.  You can do that by attempting to start the car because you'll be itching to by now anyway.  It will crank a few seconds before starting while the fuel bowl fills. If the car starts try not to run it too long so things don't get too hot to work on.
• Remove the 4 screws that hold the top of the carburetor on and the air cleaner retaining stud.  The only thing preventing the top from being removed will be the choke plate pull down rod.  Don't mess with that or the choke will need to be readjusted.  Just pivot the top and gasket to the side to allow access to the fuel bowl.

• The rebuild kit should come with an L shaped piece of cardboard with ruler marking on it.  Use this to measure the distance from the top of the fuel bowl to the gasoline.  NOTE - The distance should be measured at least 1/4 inch from the sides of the float and the fuel bowl.  Liquids have surface tension that makes the level different where they come into contact with solid objects.

• Check the specs to determine what the proper float level should be.  If an adjustment needs to be made do so by bending the tang that pushes on the needle and not by bending the float.
• The car can be started with the top off the carburetor.  Start the car and verify the float level is true while the engine is running.  If no adjustments are needed then stop the engine and put the top back on the carburetor.

Step 9 - Check For Vacuum Leaks

• Start the car.  Spray some WD-40 around the base of the carb and all of the connections that were just made.  If the engine RPMs increase when the WD-40 is sprayed then there is a vacuum leak.  
• If the leak is around one of the connections then take it off and reconnect and see if the leak goes away.
• If the leak is from the base of the carb then you can try tightening the nuts at the base of the carb but don't just keep tightening them if it doesn't go away.  There could be some old gasket on the manifold or carb spacer that's causing the problem.  If so then the carb has to be removed and the old gasket material scraped off.

Step 10 - Warm Idle Speed Adjustment

• Start the car and let it warm up to normal operating temperature.  This is also a good time to observe the carb while the car is warming up to check for leaks.  Also verify that the choke plate moves to the fully open position when the car is warm.  Make sure the fast idle adjusting screw (by the choke) is no longer contacting the fast idle cam.  The idle should be governed by the warm idle adjusting screw (driver's side of the car) and not by the fast idle screw at this point.
• Turn on the headlights (alternator should be under load)
• Put the car in the drive position for automatic transmission cars (a helper is probably necessary here) or neutral for manual cars.
• Check the idle speed with tachometer.  Adjust it to spec by turning the warm idle adjusting screw.

Step 11 - Idle Mixture Adjustment

• The idle mixture is set with the two screws in the front of the carburetor.  Both should be set 1 1/2 turns out initially from when the carburetor was assembled.
• Start by turning one of the screws inward (clockwise) until the engine RPMs begin to drop.  I usually turn the screws 1/4 turn at a time so I can keep track of how many turns out they are.
• After that turn the screw out until the RPMs begin to drop.
• Now turn the screw in again and stop when the maximum smoothness and RPMs are obtained.
• Follow the same procedure on the other screw. NOTE - after both needles are done there should be no more than 1/2 turn difference between them.
• If this procedure fails to yield satisfactory results you can try setting the needles how they were before the rebuild if you note what they were.
• The warm idle speed may need to be adjusted again after the mixture is set properly.

Step 12 - Anti Stall Dashpot Adjustment (Automatic Transmission Only)

• This should be done after the warm idle is set as adjusting  the warm idle will change this setting.
• Use a flat bladed screwdriver to depress the plunger on the anti-stall dashpot.
• Measure the distance from the tip of the depressed plunger to the throttle lever.
• Adjust the distance to the specs and install the retaining nut for the dashpot.

Step 13 - Cold Idle Speed Adjustment

• This must be done when the fast idle screw is resting on the index mark on the fast idle cam.  You can set it there manually or you can wait for the engine to cool off such that the choke will reset and create that scenario.  Either is fine.  Observe that the throttle is held open by the fast idle adjustment screw when the choke plate is closed but when the plate is open the fast idle cam is moved away and that allows the warm idle screw to govern the idle speed.
• With the fast idle adjusting screw on the V mark observe the idle speed with a tachometer.  Adjust the fast idle speed to specs by turning the screw.

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