1985 CB650 fuel leak

[R6_kid:Me]

My carbs have a persistant, but intermittant fuel leak. I have replaced the float valves but that hasn't seemed to stop the problem. The float level is non adjustable (wtf!?).

I have checked the drain valves to make sure they are sealing, and they are. But still the fuel leaks from the carbs.

The fuel appears to be coming out through the drain valve breather, which would lead me to believe that the bike should be flooding, but yet it runs perfectly fine, except that there is fuel pissing out of the fuel drain.

One time I lost approx 8L of fuel over a 4hr period. And yet sometimes it doesn't leak at all...

Does anyone have any clues as to what the problem would be?

Even when the bike is running fuel will (sometimes) leak from the drain tubes.

[xwhatsit]

Ehehehe I was fucking WAITING for the first thread of this sort from you


Anyway, what do you mean non-adjustable floats? Are they plastic, mounted with a steel tang? You just bend the little tang, but you don't need to go too far.

I'm sure you're not silly and you've given them a real proper good clean, but as I'm sure you're aware if there's even a tiny bit of dirt that gets onto the float valve seat then it'll cause a leak.

[R6_kid:Me]

The float valves slide in to an all plastic float. There is no metal tang - i know what you're talking about though.

Could possibly be dirt, think I might go to supercheap and get an inline fuel filter.

[guzzi_nz]

yep know what it like My guzzi keep doing that couldnt get it to stop some days go for months then come out it leaked petrol into bores and out back of carbs so i fixed it other way i put a lpg shut off vavle in the line and wired into kill switch 4 years not turning fuel off and not 1 leak

[CookMySock]

What is a drain valve breather? Perhaps you mean the float bowl overflow?

Is this an inline4 engine? Four carbs and they all do exactly the same thing? If so, I would say the fault lies elsewhere - maybe fuel tank not breathing properly. Try releasing the tank pressure through the filler and see if the carbs stop dripping.

Steve

[Taz]

On the old CB's the brass seat part of the float valve (the part that pushes into the carb casting) had an o'ring around it to stop gas bypassing the float valve assm. Check and replace these orings if you havent already.

[FROSTY:Me]

Dude the problem is you are from the wrong generation. You need to turn the petrol off after a ride.
If my memory is correct you have on off and reserve on your fuel tap.
Not taking the piss here mate it was just one of those things you always used to do.

[guzzi_nz]

U are right there too 70s 80 s u had to turn fuel off late 80 90s it turn off by the motor vacum (not miss print just cant spell for shit)

[R6_kid:Me]

I think xwhatsit was on the money here. I took the fuel tap out of the tank and whaddayaknow... it's full of crap and bits of paint and shit. The reserve filter was fucked and presumably letting crap get through. Upon more thought i realised it does it most/worst just after I've refueled having run on reserve for a short time.

I've replaced the fuel tap and also installed an inline filter.

Frosty, I have had bikes from this era before, and have never had to turn the fuel tap off when not riding, except for when leaving it for more than a few hours.

It started happening yesterday straight after I had put $10 of fuel in, and i don't think you expect me to ride with the tap set to 'off' as I wouldn't be getting any fuel at all!

[MSTRS:Me]

I think xwhatsit was on the money here. I took the fuel tap out of the tank and whaddayaknow... it's full of crap and bits of paint and shit. The reserve filter was fucked and presumably letting crap get through. Upon more thought i realised it does it most/worst just after I've refueled having run on reserve for a short time.

I've replaced the fuel tap and also installed an inline filter.

Frosty, I have had bikes from this era before, and have never had to turn the fuel tap off when not riding, except for when leaving it for more than a few hours.

It started happening yesterday straight after I had put $10 of fuel in, and i don't think you expect me to ride with the tap set to 'off' as I wouldn't be getting any fuel at all!

Sounds like crap getting through to the carbs, for sure. The bits of paint/whatever are catching in the float valve/s which stops them sealing, hence fuel keeps flowing. I hope you've stripped and cleaned the entire fuel system, carbs and all? Cos you need to.