Dellorto atomisers

[Daggs]

Referring to original 18mm carbs. Does anyone know which Dellorto atomiser is the leanest through to which is the richest ?

[Grumpy225]

If I understand them correctly they don't really work like that. The rich/lean parts of the atomizer covers different ranges in the carb.


Like a -1 might be rich on the bottom and lean on the top where a -2 might be lean on the bottom and rich on top and so on.

the common one is the -2 but I run a -4 in my SR190 top end (Sh20 carb), the -4 has a richer bottom end and a slightly richer top end than a -2.

Best bet is to research what everyone else is running so you get your brain around it and then start jetting.

What's the motor spec?

[Norrie Bodge]

This will help - http://forums.fourtitude.com/showthread ... 0c9a927b0f

Listen to what he gotta say in video

[fastfrog]

holes are braking gaz flow and make it harder to be sucked in the venturi. The more, the bigger and the higher the holes are drilled in the atomizer, the leaner becomes your mixture at small throttle opening. Same for the bottom section (closer to the jet) of the atomizer.

[Daggs]

Thanks to all respondents. That enlightens me .............. a bit.
I'm running a standard 150 engine through a Dellorto 18mm and a twin-pipe teapot (i know, but i like the sound) Scooter starts fine, goes off the line nice and when cruising on the main jet is a dream. It's the bit in the middle that is a little 'burbling' and uneven. I feel it's over rich. Currently running a 5899-2 atomiser, but i think i need something leaner, hence the question.
( for info. the scooter originally had a standard 38mm exhaust, but performed exactly the same as it does now on the twin-pipe)

[Doom Patrol]

It sounds like you might need something with a bigger hole in the middle then, if I follow the logic. Although, could that not also be where it comes off the pilot?

[Daggs]

I'm a sure as possble that the problem comes in just before the main jet becomes active.
You say a bigger hole in the middle. In the past, i would have thought that meant more fuel. But reading answers on this thread, it seems to suggest more air?

[sean brady scooters]

different slides can affect things also dont forget ,i think there is a choice of two for the 18mm carbs ..the difference being the size of the cut out on the back of the slide .

[Daggs]

Good point. I hadn't considered that. Do you know what difference is created by the smaller cut-out compared to the larger?

[sean brady scooters]

the larger the cut out the weaker the slide