Finer tuning for the Dellorto PHBH Carburettor

Lambretta and Vespa scooters emerged from their Italian factories with Dellorto carburettors fitted as standard, and despite an Amal on my liquid-cooled TS1, I still know, love and understand a Dellorto carburettor. Well, understand to the best of my ability that is.
The PHBH model of Dellorto is a popular aftermarket option for many of us who have tuned our classic scooters in one way or another. I’ve tried other carbs, mainly from Japanese manufacturers, but have never really got on with them. Not like I have with a Dellorto PHBH. The Italian carbs seem so much more straightforward and the options for tweaking and fettling (i.e. the range of jets, needles and atomisers) are pretty vast. Just the other week I was re-configuring a 28mm version for an engine that had previously suffered wear and manifold splits, and within a short space of time I was back on the road with performance and fuel economy as they should be.

Anyway, this week I found a social media post buried somewhere about a new range of needles produced by MB Scooters. While Dellorto jets make numeric sense (a size 125 has a larger bore than a 120, which in turn is larger than a 115 for example), the needle names don’t; the X7, X13 and X2 range from lean to rich in that order.

However, to make things even easier for those who juggle needles and atomisers in a Dellorto PHBH 28 or 30mm carb, MB Scooters have produced a new addition to the range of needles. Regarding the X7, X2 and X13 which are those mostly likely to be used on a scooter ending, according to Mark, “All three needles use the same tip and the same diameter, all that changes between them is the length of taper. The X7 taper is 20mm long, X13 22mm and X2 is 24mm. The longer the taper the more fuel can get past – so richens up the jetting.”

If you fettle these carbs you’ll no doubt be aware that these can in turn be adjusted with the securing circlip, and then even finer fettling is possible with the addition of a little washer too. Personally, I’ve never bothered with the washer, preferring (if that is the right phrase!) to pursue jetting perfection with the right mix of needle, atomiser and jets. Until now maybe…

You see to avoid the need for said washer, MB Scooters have made in-between needles based on the taper lengths. From weak to rich there is now; X7 = 20mm, MB X7/13 = 21mm, X13 = 22mm, MB X13/2 = 23mm and X2 = 24mm.

If you’re interested MB Scooters’ needles and atomisers are available separately and also as a set of needles or a set of needles and atomiser. And they include  two circlips in the sets as well, just incase you lose one. The needles along cost £5.76 each, four needles with two circlips £14.40 and four needles, two circlips and two atomisers for £18.40. For more information visit the MB Scooters website by clicking here. 

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