Scooterotica

Is there a commonly used range of D needles with an easy guide for lean to rich - like is available for the PHBH carb i.e X12 - X7 - X13 - X2 - X25 ?

I'm sitting too rich on a D29 on the top clip so don't know where to go - and I don't really understand the charts showing diameters and tapers lol.

Have a look here:-http://www.thisoldtractor.com/dellorto_ ... ides-.html
Looking at the chart D21,D22,D28,D29 are all 2.5 x 1.8 with various taper lengths
,D22,D25,D26,D36,D37 all 2.5 x 1.4 x various tapers .
cant remember but i think the longer the taper the richer the needle
. Im Sure Dan or another adult will confirm.

The 2 commonly used needles in the PHBL25 are the D22 and the D26. Where you have 2 different measurements, in this case the taper measurement "C", D22 = 18mm and D26 = 20mm, longer = thinner and thinner allows more fuel passed it, hence as Yamlam says it'll be richer for a 2mm section in the needle movement. Raising the clip on the needle drops the needle lower allowing less fuel = leaner. Thus D22 is leaner than D26. I'd remove the D29 the numbers would suggest that it's a much leaner needle than D22 or 26.

I intend to fit one to a stage 4 GP200 over the next couple of days, possible with a V4 BGM clubman. I'm planning on D22 on 2nd clip down, AQ266 atomiser, 52 pilot, 105 main jet, 40 slide.

I have a PHBL 25 carb.I run it on a Casa 185.The carb runs through an undrilled airbox with an ordinary filter.I use a 40 slide,300 choke jet,98 main jet,47 pilot jet,an AQ 268 atomiser and a D29 needle second clip down.The carb runs a little rich,but I find thats safer.