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I have a starting problem with a PHBL25 when the engine is hot but fine when cold. It does not start well when hot unless you turn the fuel off well before you stop. It will start but either stalls or runs (do you call it 4 stroking) slowly until the surplus fuel is burnt then it revs up. Someone suggested it was spitting back into the air hose and putting a drain pipe in the hose would cure it but alas not the case. The system is breathing through a standard airbox and filter. Any help would be appreciated, thanks.

Checked the float and needle are ok? If the floats knackered it won't lift the needle and so fuel won't get shut off when the bowl is full

Strangely enough one of the floats had flooded with fuel and was replaced but it made no difference.

Tractorman wrote:Strangely enough one of the floats had flooded with fuel and was replaced but it made no difference.

Check the float valve is fully seated onto its gasket, I've had a couple of dellorto carbs where the valve seat wasn't fully tightened.
10mm socket from memory I think.

Captain Pugwash wrote:

Tractorman wrote:Strangely enough one of the floats had flooded with fuel and was replaced but it made no difference.

Check the float valve is fully seated onto its gasket, I've had a couple of dellorto carbs where the valve seat wasn't fully tightened.
10mm socket from memory I think.

I will look at this area later today, another scooter guru as pointed the fuel valve as a possible cause.

Swoped float valve with one off the other scooter and still the same. I have discovered it starts ok with the air hose removed.

What air box do you have fitted? I've used two of these carbs and have had to drill the airbox to get them to breathe properly.

Paul

Scooter Paul wrote:What air box do you have fitted? I've used two of these carbs and have had to drill the airbox to get them to breathe properly.

Paul

I drilled airbox with more holes than recommended.

you haven't said what your set up is? we've had / on goin probs round here with 25mm Dellys with a 225 rapido & a well tuned 175 thro air boxes.
are you sure the rest of your jetting's ok?

Yes.