Scooterotica

New 30 PHBH just arrived for my GT240 engine, stripped it to check what jets etc. were fitted and found:
Slide - 40
Choke - 70
Pilot - 55
Main Jet - 115
Atomiser - AS 266
Needle - x2

I'm not familiar with the AS atomisers, would it be worth giving it a go with the x2 and larget main or should I buy the normal AV 266/264/268 with x7/x13 needles to play with

Cheers

Colin

Col, what you have there is standard issue internals for a PHBH. AS atomisers are longer and leaner than AV and, as such, are more suited to bikes than scooters, in the main.

I don't know the state of tune of your GT240 is, or whether you plan to run with a filter, but I think your gut feel of starting with an AV is right, maybe an AV266 with either an x 2 or 7, to start with I'd also start with the 55 pilot. I doubt it would need a richer one than that.

Oh, your float valve will be a 200, I think. Invest in a 300 and, whatever you do, don't think the 115 will fuel you at WOT

As a reference point, a standard TS1 main jet maybe somewhere between 128 and 145.

Good luck

Cheers Paul, I was hoping you would respond I have an AV266 and x2 and X7 needles and the pilot is already a 55. Forgot to mention the float weight is 10.2 grams, am I right in thinking it needs a 9 gram float or doesn't it matter? Heavier = higher fuel level?

I have no idea what my float weight is but it is the one that came with the carb. I have never changed the float on any PHBH I have used. There is the issue of petrol ingress into the floats, although from memory I think I have only ever had this on Vespas.

If you are used to copy Keihins, you'll be well used to the issue of float height. In my experience, you don't need to be overly concerned with forever checking the the Dell'Orto PHBH float height (I don't think I ever have ) unlike Keihins.

The 40 slide is a good starting point. I have a 40 on my TS1. on the GT186, I shaved a bit off it to make it around 143, I think.

In my experience too, the MB carb rubbers are very good. I have never had one split although I do replace them every year or two.

Keep us posted, mate.

Checked my 'jet box' and have an AV264, AV268 and X2, X13 and X5 needles. All 3 floats I have are 10.2 grams including the punctured one which funnily enough came off my old T5.

change the float valve to at least a 350. (it will probably have a 250 in it which is way too small)
change the main to at least a 145
change the needle to an x13
change the atomiser to an av268

Where did you get the carb from? If you had bought it from Richard or me it would have come ready set up with the correct jetting.

Coaster,

Just for your info, the 30mm PHBH I have from Rich_T is jetted as per the GT200 kits:
135 Main
40 Slide
X13 Needle
70 Choke
AV268 Atomiser
55 Idle

It feels close, but I'll be trying a higher main as suggested above, once I have my timing issues sorted.

Thanks guys, a couple of purchases necessary and I'll be there, have the atomiser and needle already