Dellorto atomizer question

[wistah_sean]

I have an odd question / problem, I'm going to ask here just in case someone has encountered this before.

I am currently rebuilding a set of Dellorto PHF30 carbs from an SP1000 roundfin built in Dec. of 1983. I purchased new jets, needle, atomizer, and slides following Guzziology's recommendations for euro spec.

When reassembling the carbs, the new atomizer (AB 264) does not fit. It screws in two turns, than it binds. I have not / will not try to force it. Close inspection of the old atomizer reveals that its an AB1 262. I have never seen or heard of AB1 atomizers before, they are not mentioned in Guzziology and I cannot find reference to them at any of the Dellorto Parts suppliers web-sites that I can find.

The kicker is, the old atomizer (AB1 262) screws in just fine, no binding, no muss or fuss. The new atomizer does not. I have tried yet a third set of atomizers I had in hand for a different project (AB 268), and these do not fit either. So either both new sets of atomizers are defective, or there really is a difference between AB and AB1. When I look at the atomizers under magnification, the threads look the same with identical pitch, but the threads appear to be cut deeper on the AB1 atomizer than the AB.

Any thoughts or ideas? Or does anyone know where I can pick up a set of AB1 264 atomizers?

Thanks for your attention.

 

[guzzibob]

I've done a lot of messing around with various Dell Orto carbs-namely 32 PHF's on my T3 replacing the stock VHB's, PHM 40's on my big valve 1000S & PHBH 30 on my old V65, never run in to this problem. My understanding was that the PHF 30 & 32's are the same basic body, just that the 32's are drilled out an extra 2 mm. Looking at the Dell Orto tuning guide, it says nothing about a 1-prefix atomizer, just 1 set of atomozers for the PHF series, another for the PHM,s etc. I've swapped out various atomizers on my 32's, & 40's, never seen a 1-prefix atomizer, never had a problem doing the swap.

All I can suggest is, call Greg Field at Moto International and/or Gordon at MG Cycle. Good luck.

 

[wistah_sean]

Thanks for the reply Bob. Greg and Gordon have not heard / seen an AB1 atomizer either, but its clear as day on the part. Since the AB doesn't -seem- to fit, I have to consider that it may be different for a reason. The threads are pretty darn similar though.

Anyone know what the thread pitch is on an AB atomizer? I know its 7 mm, but Gordon says its smaller than 1.0 mm pitch which is the smallest his thread gauge can measure. I really don't want to chase with the wrong tap (or die)

 

[Brian UK]

I have a couple of 260AH atomizer jets in the shed, and they measure 6mm thread diameter with a 0.75mm pitch. These are from 24mm VHB carbs. I would imagine the thread pitch would be the same if the OD were larger.
Do you have a Dellorto importer on that side of the pond? If not then these people http://www.dellorto.co.uk/ are generally very helpful. An email to them might bring the answer you need.

 

[guzzibob]

Seems to me US importer is www.herdan.com I've spoken to them about stuff & they have been helpful. However, checking their on line catalogue doesn't even show atomizers, though I seem to remember buying some from them. Can't hurt to give them a call.

 

[wistah_sean]

Nobody, nowhere, has heard of AB1 compared to AB. So following the advice of a few people, I said to heck with it I'm screwin' her in today. I put a little lube on the threads and gave it a go. Once I got it passed the spot where it was binding, it went in with little resistance. I think in the end it was just tight threads, and I was being over cautious.

Thanks all for the advice.