Don't Replace it, Rebuild it. You can do it!

Are you ready to replace that old leaking sputtering carburetor? Plan on spending upwards of $80.00 for fully adjustable carburetor and $35.00 or more for a fixed jet. Have you ever rebuilt a carb? Don't be afraid of them. You don't have to be Mr. Goodwrench to rebuild them and it's not like taking apart a wrist watch. They're easy to rebuild and the cost will be between $10.00 and $12.00 with a kit from right here on ebay. If your new to carburetors the following information will help you through. When you finished you'll have a sense of accomplishment and feel silly for not making the attempt earlier. There are a few simple steps to perform prior to starting as there may be a quick fix that is even easier than a rebuild.

Troubleshoot first!

Before you do anything, Make a good visual inspection of the linkage arrangement. Take a quick digital picture if you have to or just take notes. If your engine runs at all, check to be sure the correct air filter element is in place and that it's clean. A dirty or missing element will make a big difference in the way the engine runs. Be sure the air filter housing plate is secured properly and that the gasket is in place. Next check the exhaust. While a straight pipe or header looks cool, if it is not a tuned pipe it will make a huge difference as it does not create enough back pressure. If the original muffler is still in place be sure it's not burnt out or blown. Without the proper amount of  back pressure your engine will not be able to built torque throughout the rpm range and will not idle smoothly or possibly at all. Some of the items may seem irrelevant but a little here and a little there makes a huge difference.

Next step is to check to make sure the manifold to engine block bolts are tight and that the carb to manifold bolts are tight. Now you need to check the fuel supply. Bad fuel can kill a brand new carburetor in minutes. Open the gas cap and take a whiff, does it smell like gas or something else? If it smells funky, flush the tank, fuel line, filter and clean the carb bowl. If it smells fine, look for water in the tank, yes actually look. It will settle in the bottom of the tank in the form of visual droplets. Use a flashlight if you have to but definately do the check because just a drop of water is all you need.

Quick Test:

This is a trick from way back in when we used to check our hot rods for vacume leaks. Get the engine started and get it to run on it's own even if it has to idle a little high. Take an unlighted propane torch, with the valve open half way move the tip of the torch all around the outside of the carb but not near the air intake. If there are any leaks the engine will rev as it sucks in the propane. Do not do this excessively. Just enough to pinpoint the leaks if any. Check the carb to manifold and manifold to block. Check the welch plugs on the carb and at the throttle and choke shafts. If it revs up, replace leaking gaskets or repair them with permatex. Clear nail polish, loctite or a light smear of permatex works well on leaking welch plugs and should be all that's needed. If there is no difference then you probably need a kit or maybe a good internal cleaning. In that case read on. Remove the carb being careful not to bend linkages or springs. Remember, take note of linkage positions.

Disassembly:

Use caution when disassembling the carb. Clear your self an area so you can work like a gentleman. To remove the bowl turn the carb up side down. Remove the nut holding the bowl in place. Some may have a needle valve and some may not. Carefully lift off the bowl. It may need a very slight twist to break it free from the gasket. Keep the carb up side down and do not shake it. Put these parts down in the order that they were removed as it will aide you in reassembly. If you wear glasses put them on now! Next slide the pin out that holds the float in place. Look closely for the tiny wire spring that controls the flow needle. This will be between the float arm and needle and is actually a linkage that pulls the needle away from the seat to allow more gas to flow into the bowl. The float, needle and spring should now be free from the carb. With compressed air and a blow tip, pump air into the fuel line inlet. This will blast the needle seat out of the carb. Be sure it's not pointing toward anyone. The rubber seat will fly out like it was shot out of a pellet gun and you dont want to get hit by it. If your just going to try to get away with a cleaning don't lose the seat. Next remove the throttle plate, shaft and shaft gasket bushings as well as the choke assembly and gasket bushings. Pop out the welch plug and remaining adjustment screws. Check your parts, make sure everything is accounted for.

The Dip:

With carburetor cleaner or fuel injection cleaner, dip the carb. By dipping I mean fill a bowl and soak the carb body for an hour or so. Put the throttle plate, shaft and choke parts in there as well. When they come out they can be cleaned up with a soft detail brush or parts brush. Do not use anything to clean the ports other than compressed air. At this point everything should be hospital clean. Your new kit will have all the new replacement parts included except for the float and bowl. The float can be checked simply be seeing if it floats and the bowl just needs a visual for pin holes or dents. If it has large dents, replace it as this will effect the holding capacity and the engine may starve for gas.

Assembly:

By now you should know the carb inside and out and if you cataloged the parts as you disassembled it you will have no problem reassembling it with the new parts. When installing the new welch plugs use a drift the same size as the plug. Do not depress the center of the plug when tapping it home. Seal it with clear nail polish or loctite as described above. Install throttle and choke assemblies with bushing gaskets. Install the new seat. A flat faced drift the same size as the seat will help with this step. Be sure it's straight, completely seated and not deformed. Install the needle, spring and float with the retaining pin. Hold the carb up side down to do this. Reinstall the bowl with the new gasket. Install the new adjustment screws. Do not over tighten them as they will be damaged. Just enough so they are seated. Your ready to reinstall the carb. You can take it from here. Bolt torque should be 40 inch pounds.

Initial adjustment:

Back the adjustment screws out 1-1/4 turns. This will be sufficient to get the engine running and warmed up. Install the air cleaner with a new filter. Start the engine and run at half throttle for 5 minutes to bring it up to operating temperature. Turn the idle screw to obtain 1750 +/- RPM. Turn the idle mixture screw clockwise slowly until engine begins to slow. Then turn the opposite direction until it begins to slow. Turn it back to mid point. Move the throttle from idle to high speed position. The engine should accelerate smoothly. If it doesn't, open the idle mixture needle screw 1/8 turn. It can be fine tuned from there depending on barometric pressure and humidity. That's it, congratulations your finished!

More information on surging and loss of power in our detailed Trouble Shooting guide.

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Happy Trails, Chuck at Valley Farms