This may be a weird question.
Because my 3W50 always spits a lot of fuel back I would like to know of my brandnew DA50 does the same thing. The carburator of my DA50 ends in the wooden fuselage and I wouldn't prefer to end with a soaked fuselage after a few flights. BTW is it normal that my 3W50 spits a lot of fuel ?
THX for your comments.

Very common, a stack or filter largely cures it.

Install a stack. This will address the problem. The carb will still spit the fuel but the stack will hold the fuel until the next cycle where it will be sucked back into the engine.

On a reed valve motor (3W or DA) you can get the fuel to spit out of the carb from only two causes. You could have a bad reed, which allows air/fuel to get blown back out of the carb. Or you may have the carb in a position where the prop blast blows over the mouth of the carb and pulls fuel into the air stream. The DA is less likely to have that problem because it has a rear carb and the engine will shield the carb from turbulence in the cowl.

Piston port engines sometimes spit back fuel,depends on how it's ported..Reed valve engines do not...The 3W is a reed valve engine..When the piston comes down the reeds close off the intake...If the reeds don't seal well there will be fuel spit back..Otherwise it can't happen...
Leaky reeds also cause hard starting...Part of the crankcase pulse leaking past the reeds won't let the pump in the carb work well....

Is there any guideline for how long before a reed valve needs to be changed ? What is the average life time ?

I had to change the reed valve of my 3W50 recently. I haven't checked the spitting since. Could anybody explain me what a "stack"is?. Don't know the word.

Thx for the replies.

The stack that people are referring to is a "horn" that fits over the inlet side of the carb and has the effect of extending the length of the carb inlet passage. Go to the Aircraft International web site and look in motor accessories. They sell straight and 90 degree stacks.

At low mid range throttling they do spit back especially if set a bit rich- any rear intake is easy to see doing this as the spray is not blown away like the side /bottom carb setups
Hold a clean white hanky there and throttle it up and down -low rpm /see if yours does it too.

I recently bought a carb stack for my engine from B & B Spec. and noticed that it is slanted at the end, while most others I have seen have a straight cut. Is there any benefit to having the end cut slant.

If you recently replaced the reeds on your 3W-50, your excessive fuel spitting should be cured. A stack or horn will also help the mild "normal" fuel spitting.

Elson