Doh ! I can't cope with change ( & we haven't got to 1st Feb yet )
I see the Concentric Premier carb pilot jets come in different sizes to those use in the set up specifications for the original screw in & fixed bush pilot jet on the standard MK1 concentric. I can't find an equivalency/conversion table on the Amal website to work out what size to order on a premier replacement for my current concentric....but have found this guidance googling:
https://www.britishmotorcycleparts.co.nz/amal-premier-pilot-jets
Is this correct ?
I want to know which is the best fit new style premier pilot jet equivalent to 20 and a 25 ( in old money)
Very grateful if someone has found the official advice on conversion/equivalent and can point me at it.
Have you given Burlen a ring? I have found them very helpful in the past. Failing that, Hitchcocks have someone who is pretty good at sorting out carburettors - they are also Amal agents
My vote for Hitchcocks.
FOR INFO
Burlen said:
There isn't a strict equivalence between the drilled Premier jets and the 124/026 type which are flowed. The 17 size of Premier jet matches the diameter of the old 622/107 Concentric pilot bush which was roughly equivalent to 23cc. The 17 jet should be fine for your bike.
&
The 17 Pilot Jet would be the closest choice for your carburetter if you have been using a 23cc Pilot Jet.
neither of which quite answered my question of what would be the closest premier pilot jet equivalent to a 20 screw-in pilot jet ( which I currently use on my 626 concentric)
So I emailed Hitchcock's who said:
The premier pilot jet size compared to the original pilot jets are as follows;
1 Ring - 622/502-15 (Equivalent to 20 Pilot Jet in pre-Premier carbs.)
2 Rings - 622/502-17 (Equivalent to 25 Pilot Jet in pre-Premier carbs.)
3 Rings - 622/502-19 (Equivalent to 30 Pilot Jet in pre-Premier carbs.)
4 Rings - 622/502-21 (Equivalent to 35 Pilot Jet in pre-Premier carbs.)
5 Rings - 622/502-23 (Equivalent to 40 Pilot Jet in pre-Premier carbs.)
Having done a little research Burlen fuels, the current Amal manufacturer don't differentiate between the old/new pilot jet position, presumably if the original bush pilot jet is removed (completely unrestricting the pilot circuit) which would then be metered down to the required flow with the screw in pilot jet. With the new system the removable pilot jet sits in virtually the same place as the original pressed in bush, so the metering would presumably be ok at the correct sized removable pilot jet.
(I had also queried whether the change of pilot position might affect the best size)
I'm left wondering where Hithcock's and the NZ site got their equivalence table from & why Bulren suggest a 17 & don't really answer the question ( unless it's just that 17 is what Amal/Burlen fit as standard.)
Sounds like a 15 or a 17 for me and no way around just experimenting to find the best at my cost of £12 or so for the extra pilot jet.
Ah ha.
looks I misunderstood Burlen's reply & there was some lost in translation on at least my part RE "bush"/ "jet"
I now see Burlen's comment referred to the original Premier "622/107 Concentric pilot bush " ( now replaced by the new range with sizes 15 to 23 ( 1- 5 rings) ..............and not the pressed-in fixed bush on a non-premier carb, which the Amal website tells me is 20cc/min
So may be more chance the 17 might be ok on a 626 premier for my B40 star
( with a 160 main jet, Slide 3 & 106 needle jet. Will see in due course no doubt.