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Discussion Starter #1
Hi,

I recently bought a second hand 1981 KZ750. This is my first bike, and therefore I failed to pick up the leak during my initial inspection. But I got a good price and the rest of the bike looks to be in great shape, so I'm not too ****ed off about it. And besides, part of my buying an older bike was because I wanted to learn how to maintain it and fix any problems that arose myself, so I guess I got what I wished for.

The problem is one of my carbs is leaking from its overflow tube, and I'm not exactly sure why. I assume it's because the float is faulty and is failing to close the valve that allows fuel into the carb, but because I'm not an expert and therefore a little reluctant to just blindly start pulling things apart, I thought I'd try to get some other opinions from other people in the know.

I have a video up on youtube that shows exactly what's going on:

YouTube - 1981 KZ750 - Fuel is leaking out of one of the overflow tubes.

As you can see, if I raise the end of the overflow tube above the level of the carb then the leak stops, but as soon as I drop it below that level fuel starts quickly leaking out.

Any thoughts or advice on how to further diagnose and fix the problem would be much appreciated.

Thanks!!!
 

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Carb floats can some times fail and fill up with gas, Do this first:

1. Turn off the gas.
2. Remove the float bowl of the leaky carb.
3. Carefully remove the float by pulling out the pivot.
4. Catch the needle valve as it will fall once the float is removed.
5. Shake the removed float and see if gas is in inside.
6. Inspect for crud in the seat of the needle valve.
7. To clean the seat of the needle valve, get some Brasso or other metal polish, a cotton swab(Q-tip) and spin the swab with your fingers, polishing the shut of valve seat.

I'd suggest getting some rags to catch any dropped screws/parts.
 

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I know everyone has their own ways of doing things but I wouldn't attempt to remove a float bowl on an inboard carb on my bike before removing the carbs. And there is no way I'd attempt to make adjustments/clean it while it's still installed on the bike, inboard or outboard.

You could have a problem with a float going bad but I suspect it's more likely a dirty or bad float valve but it could be the float height adjustment. A piece of wood dowel sharpened with a pencil sharpener also works well to clean the float valve seat when there is hardened crud in it. Just press down a little and spin it like a drill bit.
 

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Discussion Starter #4
Hi MFolks and StarGate,

Thanks for posting - your help is much appreciated.

After reading both posts my first inclination is to just try and do this without having to take out the carbs, as I've never really done this before and I feel that the less I take apart the less I'll have to remember how to put back together again (and the less I can screw up!)

BUT

When I really think about it, I should really take the time to take the carbs out, because then when I start pulling them apart and cleaning them I'll be able to see what's going on in there. It gets pretty tight in there, and given that I'm a novice there's only so much I can do by touch and feel.

BUT

If i pull them all apart I'll have to re-sync them all afterwards as well, which will be a pain in the a**!

Not sure - I'll have to think a little further.

Thanks for all your help. If you have any further advice I'm all ears!
 

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Discussion Starter #5
Hang on - do I need to re-sync if I don't actually take the individual carbs apart? If all I do is remove the float bowl from the leaky carb, fix the float or float valve or whatever is causing the leak, then put the float bowl back on, do I still need to re-sync???
 

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That in it's self will not be cause for resync. But for best engine performance, you should plan on doing a valve adjust and carb sync in the very near future along with giving it a complete tune up.
 

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Discussion Starter #7
That in it's self will not be cause for resync. But for best engine performance, you should plan on doing a valve adjust and carb sync in the very near future along with giving it a complete tune up.
Are the valve adjust and tune up best done while the carbs are off the bike?
 

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Well you should have the tank off if you pulled the carbs so that is one thing that would be out of the way for a valve adjust. And you'd need the tank off to do the carb sync and replace plug wires if that's needed. You can do a manual sync while the carbs are off but I'd still plan on using a set of gauges or home made manometer to sync the carbs and they have to be installed for that. You could also do some other checks like coil input voltage while you have the tank off.
 
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