Author Topic: 1980 Honda CB750C leaks fuel from carbs  (Read 616 times)

Offline fourmj

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1980 Honda CB750C leaks fuel from carbs
« on: Jul 01, 2017, 22:51:45 »
Hey guys, I just finished wiring my 1980 Honda CB750C and I tried to run it. The electronics work fine, but there's a lot of fuel leaking from the carbs and I'm not sure why. These carbs haven't been altered in any way since they were taken off the bike 4 years ago. They've been wrapped in bubble tape and stored in my basement since then. I also put on a new air filter (this one:

Here's a video of the fuel leaking from the carbs (this is also running without the exhaust pipes on, but I don't think that should matter):

Any help on this would be appreciated!

Offline TheCoffeeGuy

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Re: 1980 Honda CB750C leaks fuel from carbs
« Reply #1 on: Jul 04, 2017, 12:16:41 »
your floats are frozen.   Even just sitting, oxidation occurs.  they need to be taken off and stripped out and either manually cleaned or cleaned with an ultrasonic cleaner.   left alone all the rubber also hardens and does not seal.  Your floats are frozen open. Not your ordinary Blog site.

1968 Harley Aermacchi ML 125 Rapido, restored
1972 Honda Cl 450 engine rebuild, a day rider soon, now sold
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Offline 307DeadShot307

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Re: 1980 Honda CB750C leaks fuel from carbs
« Reply #2 on: Jul 12, 2018, 12:59:17 »
Thank you. I am also having a similar problem. I pulled my carbs and applied grey gasket maker and it still leaks. I'll be pulling them this weekend and trying again. I have an ultrasonic cleaner, a small one but still, and I'll give this a try.

Offline advCo

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Re: 1980 Honda CB750C leaks fuel from carbs
« Reply #3 on: Jul 12, 2018, 14:25:43 »
Before you take the carbs apart, turn the fuel petcock to the ON position.

Once fuel starts leaking out (from the overflow I presume), take the butt end of a long screwdriver or end of a wrench and go around tapping all 4 bowls. If the carbs were clean when they were put away, often times this will unstick the float/needle valve and you'll be good to go.