Sticky Carb

[MK1953]

I bought a 1978 CB750K a year ago. It's a very clean 15-thousand-mile bike. It sat for a little over 2 years before I got it. Carburetors were rebuilt, according to the paperwork just before being stashed in the garage. When I got it home I tried to start it but no joy. Number one carb started leaking and I feared that a gasoline fire might erupt so I stopped right there. I went back to work on my 1959 Triumph TR3 but now that it's getting close to complete, I'd like to take another stab at the 750. Is there any chance I could remove the carbs and wash them down with carburetor cleaner, reinstall and start the bike or should I spend the 500 bucks to rebuild the carbs again. Thanks for the feedback!

 

[brettp]

$500 bucks?! Is that US dollars? What could possibly cost that much? Your fuel leak is most likely from 1 of 2 things: a float Thai didn't seat right (which can sometimes be fixed but tapping on the carb bowl with something firm but not a hammer), or the fuel rail between carbs 1 and 2 (which is fixed with a couple orings).

 

[dirtdigger]

The float could be bad, could have some stuff gotten in the fuel that is holding the needle open. This year will have a "rubber" tip on the float needle and normally work well....some cheap aftermarket needles have a rubber that reacts with ethanol and can swell up causing the needle to stick and leak. Like said I would first try tapping on the float bowl with a screw driver handle see if it stops leaking if not pull the bowl and take a look see if you have a needle stuck.

 

[nighthawk mike]

High probability of a stuck needle. Tapping the side of the bowl will usually knock out free. A set of new ones would be a good idea. Does the $500 rebuild include a set of carbs

 

[madmtnmotors]

Do a "clear tube test" to check the fuel level in the bowl. These carbs are easy since the drain screw is tied in with the overflow tube. This will give you an idea whether the float height is off or if one of the brass overflow tubes may have a split in it. The brass overflow tubes will occasionally split along their seam, not very often but it can happen.

 

[hinksy]

It isnt too hard , but lotsa bits . Take off the tank , remove airbox and then throttle cables . Now you can take off the carbs in one piece . The screws are not phillips heads , they are JIS . If you dont use a JIS screwdriver , you stand a chance of stripping them . Lots of videos of people cleaning them on the youtubes . Do a search and have a look