I have a small drip in the drain plug at the bottom of my carb. I tried to tighten but it doesn't get tight just gets to one point then slips. I looked at the threads in the carb and there isn't alot left on them. The plug threads look fine. Any way to get the plug to tighten up. I ran a tap in there 3/8 24 and it didn't do anything to clean up the threads. The plug does thread in just doesn't get tight. Helicoil? Tap one size bigger? Teflon tape? Any help would be appreciated. Thanks Keith
Carb drain plug not tight
- Thread starter 1929tudor
- Start date
Ron in Quincy
Well-known member
Suggest you put a light coat of Peratex Avation Gasket Cement on each side of the gasket and on the threads of the plug; this is gas resistant cement and may solve your problem.
Ron
Ron
Tom Wesenberg
Well-known member
Permatex makes a thread repair that worked fine for my motorcycle mirror that fits into the aluminum handgrip bracket. If that doesn't work, I'd try a heli-coil.
700rpm
Well-known member
If I remember rightly (admittedly questionable), that is a pipe thread. A 3/8-24 will only make it worse. If I remember rightly. 
UPDATE: tbirdtbird corrected me on this. He says it's not a pipe thread (below, #11). Thank you. I didn't have a firm idea about that , and remembered wrongly.
UPDATE: tbirdtbird corrected me on this. He says it's not a pipe thread (below, #11). Thank you. I didn't have a firm idea about that , and remembered wrongly.
Last edited:
Tom Endy
Well-known member
I have made such a repair several times by doing the following:
Obtain an old (or new) strainer assembly that screws into the top casting. Remove the screen from the cap by melting the solder. The threaded cap is similar in shape with a cupped reservoir as the drain plug cap, only it is larger. The drain plug has a 1\2" hex, the filter screen cap has a 5\8" hex.
Drill out the drain hole with a 29\64" drill bit being carefull not to molest the boss for the main jet. Thread the new hole with a 1\2-20" (fine) tap. Use a bottoming tap to finish up.
The new cap will work fine, only it will have a 5\8" hex that will irritate the purests.
Many of these drain plugs have been stipped out by being over tightened. An owner is lulled into the belief that the drain plug is leaking, so he keeps tightening it. What is actually happening in most cases is that the float valve is not holding and the fuel level in the bottom casting reservoir begins to rise. So does the fuel level in the main and cap jets. When it spills over the top of the two jets it runs down into the throat of the carburetor and exits through the small drain hole drilled in the bottom of the casting. From there it runs back to the hex on the drain plug and drips off from it leading to the belief the plug itself is leaking.
Tom Endy
Obtain an old (or new) strainer assembly that screws into the top casting. Remove the screen from the cap by melting the solder. The threaded cap is similar in shape with a cupped reservoir as the drain plug cap, only it is larger. The drain plug has a 1\2" hex, the filter screen cap has a 5\8" hex.
Drill out the drain hole with a 29\64" drill bit being carefull not to molest the boss for the main jet. Thread the new hole with a 1\2-20" (fine) tap. Use a bottoming tap to finish up.
The new cap will work fine, only it will have a 5\8" hex that will irritate the purests.
Many of these drain plugs have been stipped out by being over tightened. An owner is lulled into the belief that the drain plug is leaking, so he keeps tightening it. What is actually happening in most cases is that the float valve is not holding and the fuel level in the bottom casting reservoir begins to rise. So does the fuel level in the main and cap jets. When it spills over the top of the two jets it runs down into the throat of the carburetor and exits through the small drain hole drilled in the bottom of the casting. From there it runs back to the hex on the drain plug and drips off from it leading to the belief the plug itself is leaking.
Tom Endy
gweilbaker
Well-known member
Something I have learned from this hobby~ not when you need one and when you do find one, it is in worse condition than the one you have!
Purdy Swoft
Well-known member
I once broke the lower casting of a Zenith carb in half tring to remove the secondary well. I called Berts in Denver (800-321-1931) and trhey sent me a GOOD used lower casting at a very reasonable price.
tbirdtbird
BANNED
it is not pipe thread