Topic: leaky carb

[1978CB750SS]

So I been adjusting these carbs for a while. I read all about how to adjust floats and do the tube check.Only trouble is, I'm low on green so I fix up the old parts If I can. I added some solder to the leaky brass floats, I got to thinking with the added weight I must compensate for a float that will not be as buoyant as the others. Well anyway, as I ride sometimes going city speed or stop lights the number 1 carb starts to leak. I was turning the petcock on and off at idle or low speed. I thought I had it so there would be no trouble as long as I shut petcock off. I cut a piece of pepsi bottle and shoved it under the leaky carb to catch gas and see when it does leak. After the ride today which was about 20 city, 30 highway miles all is well, no leaks at any given rpm with petcock on. I'm not convinced it is totally fixed, but I am wondering why it leaks.The overflow tube is not cracked, a different one was and I soldered that as well and it is fine now.I think letting the bowls get too low is not good for the moving parts either( float and needle may stick open), and it can be dangerous as the idle is uncontrollable at that moment as the gas gets too low the idle climbs. So at a light I'm checking for neutral,( light is out) turning petcock, holding clutch,using turn signal and balancing old lady on a high center of gravity bike. All that crap combined can be not good.I just take my time and I hope it is fixed for good this time.If not I will lower  the fuel level and see if that helps. I may need new floats, needle and seats to be free of the gas problem.

[BomberMann650]

You're doin too much thinking 

Use the clear tube method to verify fuel levels in the bowls.

[1978CB750SS]

Thats the prob...I did. And I still was getting intermittent leakage, must be sticky float needle.I may have got it right this time,we'll see. I work tomorrow but can ride tuesday and wednesday! So I'll get some more time to check things then and dial her in. lol

[BomberMann650]

Sometimes a piece of rubbish gets caught in the float valve.  Best to remove the float and needle, use a dental brush to cleah the valve seat.  And inspect the tip of the needle for wear.

There is also a chance that your solder didn't fix the overflow stem.  I think someone here used shrink sleeve on their tube in lieu of solder.

[markreimer]

I had a very similar problem on my 750 K4 this month. The carb body for #1 would leak. Sometimes just a little, sometimes a steady flow. I pulled them off and verified the float height was correct - yup, all four identical. Put it back on the bike and was greeted with a steady flow of fuel onto the shop floor, what!?

So I removed the float bowl entirely (with the petcock OFF), put a little empty margarine container under it, and turned on the gas. With the float just hanging there, gas flowed through as fast as possibly. I flicked the float up and down repeatedly to try and shake any debris that might be hung up in there.

Put the bowl back on, no more leaks at all. I guess I had something stuck on the tip of the float needle or something. Worth a look.