dellorto phf 35 floods

Hello from Canada
I’ve got a pair of carbs off a Cagiva Elephant that are acting strange. I am trying to set the float height on them. I can test them on the bench with a funnel and a tube feeding the carb and all is good. The bowls fill and the level in the funnel does not drop after a couple of beers. However when installed in the bike they starts pissing fuel as soon as the petcock is opened. What the Hey? The only thing wrong that I may have done was that I adjusted the needle tab instead of bending the float arms but either way it still got me to where I want to be 18mm +/- .5. Which I will recheck.
I cant understand why it holds fuel on the bench but not on the bike. Accelerator pump?
One final question. What is the small tube with the check ball for? Hangs in the float bowl. Air bleed?

I don’t think it is the pump mechanism - this only gets operated at larger throttle openings.

You asked about the brass tube with the ball bearing in the end - that is the feed to the accelerator pump. The ball-bearing
acts as a non-return valve which allows the pump to work.

Have you tried measuring the float level on the bench with the carb at the same angle as it sits on the bike?

Have you replaced the float needle? Sometimes the ‘rubbery’ bit on the end can decay, although I thought this would have caused problems
on the bench as well.

Good Luck!

Back at er. Found float height info and set it to 18mm the proper way. seats hold when i blow in the inlet. Works for every other bike ive had so Ill call em good. I am concernerned it may be the accelerator pump. With the carb empty the plunger is recessed a few thou but with it primed I dont know were it sits.
Anyone have a setting for this? Turns out from all the way in or something?


Have you tried installing the carbs on the bike with the float bowl off. Put a suitable container below the carb to catch the petrol and turn on the petrol tap. Lift the float with your finger gently and see if the flow stops.

No substitute for doing it on the bike when you get a different effect on the bench. The pressure from the tank may be much higher than you are getting using a funnel. Personally I have a small container hanging from the garage ceiling with a tap and tube. This is a much better way to make sure they work right at slightly higher pressure.

You could contact Dellorto - they have a technical advise option via email. You can also buy anything you might need from them.



have you solved your flooding problem? I have exactly the same problem with PHF36. They were behaving OK unitl I cleaned out jets, set correct float level. Started flooding so I replaced needle and seats. Flooded. I altered float height to be greater than quoted level, both by bending float arms and by bending needle tab. No different, floods. As with yours, with carby upside down I cannot blow through inlet so needle is seated. If I hold floats up by hand fuel does not get past neddle. Until I put the blasted things onto the bike. It happens to both carbs at differeng degrees.
This started after cleaning them.