After change of needle and atomizer the engine dies at 3/4 -full throttle. The needle and atomizer were worn out.

I have checked almost everything, 4-5 times, involved in the fuel part.
Floathight set to 17.5mm.
New fuel filter, cleaned tank and "tanktap?" (outlet from tank).

The carbs are cleaned and blown with compressed air back and forth thru all jets.

The engine starts and idles fine. When the throttle goes up slow the rew increases until ~3/4, then dies, if not the throttle is twisted back. Lack of fuel.

Same throttle is ~1/4-1/3 and full throttle is set. The engine rews a bit and dies, if not the throttle is twisted back.

The bike have Dellorto PHM 40 and no fuelpump.

Now I'm very frustaded over the situation.

Any ideas?

Which rev does it happens?
Is it about 6000 rpm?
Maybe yor spark plugs suffered because of some excess of fuel in some time of carb setting. You might try to change them (the burst plugs don't look "worn")
Otherwise the elder jets weren't original and they had been "customized" compare them with the new ones
have a nice work, Nicola

I would look at the fule line and make sure it's not pinched or collapsing inside. Mkae sure it routes as much in a downhill direction as possible.

Next would be the fuel filter. Make sure it's not clogged ro too small to flow all the fuel needed.

Check the vent or leave the cap open just to make sure it not getting starved by vacuum.

The float height seems ok according to my manual. You did check them with the float to the side not on top?

I have PHF36's on my paso. Is it possible that 40's are too big and it's not starving but flooding?

Thanks for all hints, but I still have problem.

From the begining the bike had a fuelpump, which I removed succesfully.

No problem to run the bike without it, until now, when I changed needle and atomizer.

I did a flow test today.

Without carbs connected the flow was ~1 liter/min. Better than I wrote earlier.

With the carb connected and float bowl open, float not closing the flow was the same as not connected carbs.

I will try to switch back to the old needle and atomizer, just to check. But I doubt it will work.

//Anders

Well, you need to know if it's dying because it's too rich or too lean. You could try a couple of things:

Try to hold it running, but just at the point where it's starting to die, for about 15-20 sec's. Then pull the spark plugs and see if they're black or white.

Or, shut off the fuel, and as the fuel level in the carbs drops, keep trying to run the motor up to those revs. If it runs better as the level drops, before it runs totally out of fuel, it's getting too much fuel. I discovered a problem with the float height of a bike this way, totally by accident. Forgot to turn the fuel on! This bike had been giving me problems for hours and hours!

jihaa,

Problem solved!!

It was the new needle and atomizer. When I installed the old ones the bike responded as supposed to, full throttle response well above 10'rpm without load.

The suggestion to switch back came from a service shop.

I'll contact the shop from where I got the parts and try to get some explanation

//Anders