Hi folks

Recently i finished installing my bike carb setup and ran into quite a bit of trouble.

I’m running Suzuki GSF600 carbs (Keihin CVK32 with 95 main jets, fully custom airbox paired with the original airbox and k&n filter, around 12.5 AFR on the whole rev range).

They’re fully rebuilt, new floats, new main and idle jets, mixture screws, gaskets… They don’t seem to spit out anything when tested outside the engine bay. Floats are set to the manufacturer’s specs.

Fuel is coming from an auto regulated electric fuel pump (pushes .2 to .3 bar i reckon) from a Kymco ATV running the exact same carb, figured it would suit it well.

Thing is i keep flooding. Engine runs great bus as soon as i’m driving, it starts running on 2 cylinders like it’s flooding, put some gas to burn the fuel and it starts to work again until you release the gas. I tried with the original mechanical fuel pump and same issue, though less regularly. It also seems to happen when the car isn’t on flat ground or taking bumps, so maybe something going on with the float level, even though I already tried to lower it ? Thought it could also be an ignition problem but not always the same spark plugs that get dark, so ruled this out. I’m kinda running out of ideas so if y’all got anything i’d be glad to hear from you guys…

Well, found something that works. Have been trying a bunch of different things (electrical pump alone, mech pump alone, mech pump & T piece…), only on that works is the original mech pump along with the little plastic reservoir thing on the 2e3.

German documentation says it’s made solely to evacuate gas vapors, but i think it might also lower the fuel flow pressure, which would help not push in on the floats.

Have been driving the whole weekend and nothing to say, it works almost flawlessly !

More than happy to say that this thing is almost finished after 2 and a half years of hard work !

well done.

Carbs need high volume low pressure fuel.

(about 0.18 bar, unless forced induction).

Too high pressure overcomes the needle valve(s) held closed by the buoyancy of the float(s).

You are correct. The plastic reservoir thingy is a swirl pot or vapour separator. It removes bubbles

introduced by the suction pump - an air bubble won't flow smoothly into the carb wells which may be serial so last in line becomes starved - and, crucially lets excess fuel pressure escape back to the tank down the return line.

Which also has side benefit of cooling fuel, so hot restarts avoid evaporation effects.

Return line must be smaller bore than feed line.

(T piece with flow reduction on return can work but it's hit and miss).

Fuel line from pump to carb / swirl pot should ideally be short.

Golf mk2 Pierburg carb needed a larger metal swirl pot.