CB700SC: Float chamber leaking = Carb rebuild?

[Danian]

I just started up my '85 CB700SC after a winter hiatus.  While doing my safety check, I noticed fluid dripping out from under the bike.  A quick trace revealed fuel dripping out of the air hole of one of the float chamber.  Additionally, it looks like fuel might be leaking out from where the cover meets the carb.  I figure I'll try to take it to the shop tomorrow, but I'm wondering what to expect.  I'm thinking that after sitting since November, the float chamber cover gasket dried up and shrunk, accounting for some of the leakage.  And perhaps something is temporarily blocking the float chamber and building up the fuel until it comes out of the vent.

My question is if it sounds like a (relatively) simple fix or am I looking at a carb rebuild?  Is there anything I can do at home with basic tools and limited mechanical know-how or is this a job for the stealership?  I'm in San Diego, and so far, I've only found one place that will even work on my bike.  It's simply too old for anyone else to be willing to work on.

[Munkey]

Sounds like a stuck float. I think normal fuel level in the float bowl level should be below the gasket, but not sure of that. Might try tapping on the float bowl to see if it comes loose.

[Danian]

Thanks!  I'll try that before I make arrangements to have the poor thing trucked to the shop.  Letting it sit overnight in the fuel might help loosen it up, too.

[Adam Roby]

My friend's ride had a similar issue and it turned out to be the petcock was flowing when the bike was off and overflowing the carbs..  a simple stretch of the internal spring fixed it - 3 yrs now and still good.

[Danian]

...a simple stretch of the internal spring fixed it - 3 yrs now and still good.

You're right, I left the fuel petcock on.  So...this "simple stretch"...is that literally going in and stretching the compression spring?

[Adam Roby]

I would have to double check with my buddy but yeah, I remember him saying it was simply a matter of stretching, checking, stretching a bit more.. until it stopped flowing when off.

[Danian]

Well, I went out to the garage and gave the float chamber a couple of thumps with a rubber mallet and then fired her up.  No drips!  I wheeled her out to the driveway and put it on it's sidestand.  Still no drips!  I took her for a spin around the block a couple of times...first time I was gentle, the second time I opened her up a bit.  No drips!  Woo-hoo!!!

In conclusion, it really must've been a stuck float and just by sitting overnight in fresh fuel along with perhaps some gentle persuasion with the mallet, it must've worked itself free.  I'll take her out for an extended ride tomorrow, just to make sure, but I think we'll be alright as long as I promise not to make her sit in the garage for any length of time anymore.  I sure do love this bike!

Thanks to everyone for their help!

[Brittles]

Good to hear. These old bikes need to be run.

How do you like the Corbin seat? Can you compare it to the stock seat?

[Danian]

Good to hear. These old bikes need to be run.

How do you like the Corbin seat? Can you compare it to the stock seat?

At first, I wasn't sure I liked it.  It seemed awfully stiff.  But I've found that I can ride farther and longer with it than I could with the stock seat.  After a couple of years, I don't think I can go back to a stock seat.  They seem kinda mushy to me now.

[Adam Roby]

Not to sound crude but my butt goes numb after a few hours of riding with the original seat...  figure the corbin might help?

[Danian]

Not to sound crude but my butt goes numb after a few hours of riding with the original seat...  figure the corbin might help?

I think so.  It might be culture-shock when you first sit on one, but I remember having a limit of a few hours with the stock seat, too.  Now I can go about 8 hours before I need extended time off the bike.  I don't know if I'd pay full price for a new one, but it's well worth a try with a used one off eBay.

[muttstang]

I may have to pick one up someday