Carbs won't stop overflowing!

Fazer59 · L Plate Warrior Joined: 12 Jul 2019 Karma :

Hi to all.
I have an old gs400e that I was going to do the cafe number on it, but alas it is to heavy for me as I only have one arm due to a bike accident. I've now decided to just clean and re commission it as it's all original. I've ultrasonicly cleaned the carbs after dismantling them. Re assembled them replacing any o rings, set up the float heights, finished assembly and put them on the bike. Bike started fine, then petrol started pissing out of the pilot air feed at the front of the carbs.
Now, ive had them apart and checked everything half a dozen times and set them up off the bike with a temporary petrol feed and every time the same thing happens, and every time I check the float valves shut off and they do! It like the fuel bypasses the float shut off system and fills the carbs up. It happens very quickly too, almost quicker than the float system does.
I have no idea what to do next. I must add that I never started the bike before stripping the carbs, so don't know if it's always done it! I know, I should have checked first!
Any ideas would be greatfully appreciated.

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

Pictures?

My guess would still be assembly error or utterly fooked float valves/seats
or debris/detritus in supply passages despite the ultrasonic cleaning which isnt a 100% guarantee you've got all the crud out.
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Fazer59 · L Plate Warrior Joined: 12 Jul 2019 Karma :

Thank you for your reply, I'll just have to keep at it. They did have four 20min sessions in the cleaner, but I take your point. Been doing this stuff for fourty years but never experienced one like it! First time fir everything! Cheers.

Tankie · Crazy Courier Joined: 24 Feb 2017 Karma :

Check and reset the float heights
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Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Just replace the float valve needles and seats. They'll be worn and the rubber will have hardened over time.

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

Bhud · World Chat Champion Joined: 11 Oct 2018 Karma :

If the problem persists after replacing float needles and seats, fit a manual on-off fuel tap and don't forget to turn it off.

Riejufixing · World Chat Champion Joined: 24 Jun 2018 Karma :

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

Cos they is
the ones on my carbs are in a similar place
To be more precise, they keep the air pressure above the fuel in the float chamber at ambient atmospheric pressure,
otherwise the incoming fuel would get held back as it filled, especially if it wasn't gettting sucked out the jets
fast enough to lower the pressure.
They also act as an overflow when the float valves fail.
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bikers smell of wee

Riejufixing · World Chat Champion Joined: 24 Jun 2018 Karma :

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

https://images.cmsnl.com/img/partslists/suzuki-gs400e-1978-c-e01-e02-e04-e17-e18-e21-e22-e24-e25-e30-e34-e39-carburetor_bigsue0046fig-12_7618.gif

this may not be your exact bike but you know know of cmsnl, for the exploded views at least.

Picture, very high overflow tubes eh, more like float chamber local atmosphere vents ?

The small alloy tube stubs on the bottom of the float chambers would more like be overflows and/or drain tubes.

OP take some pictures and post where the fuel leaks from.
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