Topic: Leaking Drain Valve on '78 CB400A

[jeepastx]

Hey guys. I have a '78 CB400A with a stock carb that seems to have a drip leak from the float bowl drain tube that I can't seem to stop. Any ideas on a fix?

[Steve_K]

Some of the drain screws have o rings.  Check and replace yours.  Other than that maybe a cracked float chamber?
Steve

[jeepastx]

i did replace the o-ring on it but it seems to still be passing fuel through to the tube. When I saw the fuel still coming out the drain tube I figured the o-ring just kept the fuel from coming out the head of the screw. The pointed tip of the screw seems to be a little rough so I figured maybe it wasn't seating well when screwed in all the way. But I'm afraid to sand it down to try and make it smoother cause then it might not seat at all. Cant seem to find a replacement screw anywhere.

[Thekramer666]

Pictures?

[Flyin900]

The brass drain tube inside the float bowl may be slightly cracked and allowing gas to leak out. Depending on the design of the overflow tube and how it actually works it's possible that is where your leak is coming from.
If there is a crack you can either soldier the tube to reseal it or replace the whole bowl.

[Thekramer666]

Have u taken off that bowl maybe your float is sticking allowing overflow

[jeepastx]

The float seems to be moving fine. I have made adjustments to the float height per the manual specifications. I can't seem to find any replacement bowls online. The drain tube does seem a little banged up to be honest. It is slightly bent and there may be a crack in there. If I can find a replacement bowl I'll do that. If I can't find one an time soon, I'll just try and solder it as a last-ditch effort. Unfortunately I can't ride it dribbling fuel like that. That is probably the worst part of this all. If you guys hear anything that can help please let me know. Thanks for all the help so far. I guess I'll go figure out why my CR29-equipped '77 CB750K won't start.