Hi, I have what i think is a 1995 or 1994 beta techno 250 and it has a dellorto carb and it continues to overflow. I have replaced the float needle and the needle seat and i have replaced the floats aswell but when i tried bending the tabs it would either overflow or it wouldnt get any gas at all. Im stumped on what to do im not sure if i need to replace the carb or what.

you've not got the floats in upside down?? I've done that before

Sometimes the d/o floats do not float, this may be your problem.

I have checked to make suee the floats float and also i believe i have them in correctly with the pins on the float towards the bottom

Maybe you need to start again. Remove float bowl and make sure it is not distorted, in other words useca straight edge across its mating surface. Now ensure by referring to or checking against a parts list that you have everything you’re supposed to have in the carb. With the carb assembled gently blow into the fuel entry point with your mouth and with your finger gently hold the float against the needle valve, if you can’t stop your breath from entering the fuel entry point then there obviously is something seriously wrong with either your fitting or those parts fitted. Let the float drop a little, lift it back up to prove it works as it should. If there is a tickler plunger make sure it’s not stuck down. There was a need for a carb mod on later models, could be worth checking out.

Edited July 25, 20188 yr by section swept

I had the same problem with a phbh on my alpina.  The solution came from a karting site. If there is vent pipe, going from a spigot on one side to the same type on the  other side, it should have a slit in it. Mine had been 'repaired' with a joint, I drilled a 0.5mm hole and bingo.

1 minute ago, Billywhiz said:

I had the same problem with a phbh on my alpina.  The solution came from a karting site. If there is vent pipe, going from a spigot on one side to the same type on the  other side, it should have a slit in it. Mine had been 'repaired' with a joint, I drilled a 0.5mm hole and bingo.

When you say a slit do you mean in the tubing or in the actual pipe? Because there are two vent pipes that are connected by one hose are you saying the hose needs a hole in it?

7 minutes ago, Masterbeta808 said:

When you say a slit do you mean in the tubing or in the actual pipe? Because there are two vent pipes that are connected by one hose are you saying the hose needs a hole in it?

Half way along the tube cut half of the tube away with a scalpel/Stanley knife to a length of approx. 2 cm   ......this will allow air [atmospheric pressure] to enter the chamber above the fuel in the float bowl ..........if air cannot enter there [because the vents have been blocked by a piece of unvented tubing] at atmospheric pressure fuel cannot be sucked through the carb jets to supply the motor. Its a common mistake made by people who do not understand how a carburettor works.

27 minutes ago, oni nou said:

Half way along the tube cut half of the tube away with a scalpel/Stanley knife to a length of approx. 2 cm   ......this will allow air [atmospheric pressure] to enter the chamber above the fuel in the float bowl ..........if air cannot enter there [because the vents have been blocked by a piece of unvented tubing] at atmospheric pressure fuel cannot be sucked through the carb jets to supply the motor. Its a common mistake made by people who do not understand how a carburettor works.

Thank you that solved the problem it nakes sense how if theres no ventilation that it wont run i noticed it when we first got it abiut why they were connected to eachother but i just left it alone and thought nothing of it 

you will be far better off if you simply remove the connected vent hose entirely or just use a short section on either side to act as a crap deflector because that is all it really does

The bike ran for a little bit but now there is no spark ive disconnected the kill switch and it wasnt that and it has a new plug aswell i havent started testing yet but i will try tomorrow