Quick Carburetor Rebuild How-To Guide For Beginners

So you finally got around to working on that old project car you had sitting outside, eh? It happens to the best of us, you lose track of time and a car sits for way too long between drives. If you let it sit too long, your carb can get pretty gunky and may require servicing before it will actually run. Gas slowly evaporates in the fuel bowl, and this process leaves a lot of varnish on the metal. The main issue here is that the needle and seat can become frozen in place. When that happens, you will either get too much fuel in the bowl or no fuel at all. A quick carburetor rebuild can solve these issues.

When good carbs go bad

In most cases you will need to do a quick carburetor rebuild in order to make it function. While you might be able to get a sticky needle and seat to regain function, it is best to replace it as you will eventually have the same issue later one. Another issue that can wreak havoc on your enjoyment of an older car is leaky carb gaskets. Over time, as little as a year of non-use, the gaskets may shrink, causing fuel and air leaks that render the carburetor less than efficient. If you are anything, like me, you probably HATE tuning a carb. It is my Achilles heel, and I am just not good at it. You might find yourself putting off a full rebuild simply because getting it tuned will be a chore. There are options though, and as you will see here, you can refresh the internals of a carb without having to re-tune it. *(AUTHOR NOTE: You will eventually need to make adjustments, but this method will get your engine running and it will be very close to the previous tune). With the help of my daughter (this is her car), we had the VW Bug up and running in a single afternoon.

Getting started

We recently resumed work on a 1974 VW Beetle that has a performance-built 1836cc engine with twin Kadron carbs. We had the car running a few years ago, but it had sat for eight years, so the carbs needed serious work. We managed to get the needle and seats to operate, but they would stick regularly, so the car ended up sitting for a couple more years. A quick carburetor rebuild was necessary, and we picked up the parts from our local NAPA Auto Parts Store. With the carb kits in hand, we sat down and got to work on our carburetor refresh. There are several key points to this project if you want to save yourself some hassle. When removing the carb(s), simply disconnect the linkages and set aside. Do not adjust them or change anything. If you have to unthread a linkage, mark the position with tape so you can get right back to where it was before removal. 

We pulled the carbs off the engine, leaving all of the adjustments as they were. These small carbs are simple and easy to work on without changing all of the settings, but some carbs require everything be removed when doing a full rebuild. If that is the case, you can use paint or a scratch awl to mark the positions of the idle air mixture and idle speed screws. 

You will need a few tools and supplies to perform this refresh. We used Berryman Chem-Dip carb cleaner dip, which is very efficient and even comes with a parts basket in the can. This is 1-gallon and can be reused. You will also need a few hand tools like screwdrivers, sockets and wrench, and a pick. We started by removing the bolts that hold the top half of the carb to the main body. A slight tap with a wood handle or screwdriver is usually all you need to break the seal on the gasket. 

The paper gaskets had shrunk considerably since these carbs were last rebuilt, about 11 years ago. The new carb kit has all the gaskets you need. 

One this carb, the needle and seat are bolted to the top of the carb, on others it may be in the main body. This can be removed now. 

On the main body, the fuel float is secured with a little plastic “bone”, which keeps the float from rising in its mount instead of rotating on the hinge pin. The float lifts right out. You will want to check the float for signs of holes or damage. The float should float in a glass of water. If it rattles when you shake it, it is probably bad. To test a float, submerge it in a glass of water. If you see bubbles rising, then it has a pinhole leak and needs to be replaced. 

One of our carbs was badly corroded at the butterfly. We used some Mac’s Carb Cleaner to breakdown the corrosion and get the butterfly moving again. 

On the underside of the main body resides the diaphragm, this is the part that pushes out fuel when you first hit the throttle. The pump cover is removed and the small diaphragm and spring can be taken out. 

This is the extent of the disassembly we are taking on. You can remove the adjustment screws, but in this case, it just isn’t necessary. We placed all of the components into the carb dip and let it set for 20 minutes. 

After the allotted time, we removed the parts and washed them off with a garden hose. The varnish inside and outside the carb is all gone, nice and clean. 

Reassembly

At this point, we began the assembly process. It goes in reverse order of the disassembly. 

The entire quick carburetor rebuild project took us about two hours for each carb. We didn’t change any of the settings, so we don’t have to tweak anything in order to get the engine to run. Once the carbs were reinstalled onto the engine and primed via the engine’s fuel pump, it still would not run. We swapped out all the spark plugs, and it fired right up and ran like a dream. No missing, no choking out, and it accelerates very well. Before our quick carburetor rebuild, you couldn’t even get them to take fuel from the pump. 

Check out all the fuel & emission system parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on how to perform a quick carburetor rebuild, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.