Tech Tip: Amal Premier Pilot Jets & Tunning (All You Need To Know)

Tech Tip: Amal Premier Pilot Jets & Tunning (All You Need To Know)

So you purchased a new Amal Premier carburetor and noticed that your classic motorcycle is running too rich or too lean on the pilot circuit

Before you panic you need to know and understand a few things before you throw in the towel..

This symptom of a lean or rich condition is quite common on any carburetor, however, those that have the new Amal Premier carburetors or Wassell Evolution carbs will have the liberty of fine tuning the pilot circuit by swapping out the "removable pilot jets"

Should you find yourself in this predicament I recommend that you keep reading our Tech Tip post..


What is a pilot jet?

Up Close - Amal Premier Pilot Jets

A pilot jet is a circuit (or meter) that controls the flow rate of fuel that is drawn into your carburetor

Different size pilot jets can help you achieve a rich or lean condition

Not all Amal carbs have a removable pilot jet, in fact most original Amal Concentric carbs have a pressed in pilot jet that cannot be removed without some serious modifications..


How to adjust your pilot jet

Amal Fuel Mixture Screw (Concentric)

Adjusting your pilot jet on a new Amal Premier Concentric carburetor is very simple

In fact, all you need is a flat head screw driver and a sense of how the motorcycle is “responding” to your current jetting and on going adjustments

The rule of thumb when adjusting the mixture screw is a “turn and a half out”

You must turn the adjusting screw all the way in until it stops, mark it’s current location then back out 1 1/2 turns

Remember a 1 1/2 turns out is a rule of thumb, you may have to adjust the screw (in or out) more to find its “sweet spot”


Rich & Lean conditions

Champion Spark Plugs


There are 2 types of conditions when working with pilot jets (and all jets as well)


  • Rich
  • Lean


I like to throw in an extra condition that happens to be in-between lean and rich

This in-between mixture is ideal as an overly lean or rich condition can cause some serious issues


Rich conditions 


A rich condition in the pilot jet circuit usually offers a few different signs


  • Wet / dark spark plugs
  • Heavy running
  • Poor throttle response
  • Runs with air screw bottomed out 
  • Black unburnt fuel 


Lean conditions


A lean condition in the pilot jet circuit usually offers a few different signs as well


  • Back firing and popping
  • Hard to start
  • Runs better when air screw is screwed all the way out
  • White spark plugs


Rich & Lean solutions


Amal Premier Pilot Jet Grooves


Should you have a new Amal Premier carburetor the fix for a lean or rich condition on the pilot circuit is now easier than ever before


  • Should you have a lean condition, you must install a larger pilot jet
  • Should you have a rich condition, you must install a smaller pilot jet


Amal Premier pilot jets come in increments of 2..


  • #15
  • #17
  • #19
  • and so on..


Changing the pilot jet on a new Amal Premier or Wassell Evolution carburetor is quick and easy and allows you to fine tune your motorcycle like never before


Give and take

Perfect does not exists, however getting your pilot jet "close" is possible but there will be a sacrifice 

You may find that your specific application may not like a #15 but runs "better" on a #17..

Often times when this happens you will have to find a pilot jet that makes the performance of your motorcycle "run best", from there you can adjust the mixture screw 


Amal Premier pilot jet range


Here at Classic British Spares we stock a large range of Amal Premier pilot jets in all sizes 

Each pilot jet is made and tested in England to ensure accurate metering 

Should you need a range of pilot jets, please see the chart below and select the size you need for your given application:

 Amal Premier pilot jet (part #) Sizes Link
622/502-15 #15 Click Here
622/502-17 #17 (standard) Click Here
622/502-19 #19 Click Here
622/502-21 #21 Click Here
622/502-23 #23 Click Here


Click here to view our full range of vintage Triumph parts, BSA motorcycle parts and Norton Commando parts 


Thanks for reading 

Hey guys, Kyle here!

I just wanted to say thank you for reading today's Tech Tip post 

If you enjoyed reading today's topic, click here for more Tech Tip posts just like this one

As always, you can leave use a comment below to join in on the conversation 

Ride safe! - CBS


  • Terry Dwyer

    When you say one and a half turns, do you mean you turn screw one and a half 360 deg or is your interpretation of one turn from 12 o’clock to 12 o’clock?

  • sampson m keller

    I have a 1973 Triumph Trident with new Amal Premier carbs, Tri Spark ignition and 3 into 1 Hooker Headers. bike starts easy and idles ok but seems to lack power above 4500 RPMs stock jet is 150. would you reccomend and do you have a 160 or 165 main jet?

  • Ian Taylor

    can l convert a non primier idle jet set up to premier by drilling and threading the old setup ?

  • Jeff MacKay

    The Amal Premier Pilot jets do have distinguishing lines for each size.
    1 Ring – AM/622/502/15 (Equivalent to 20 Pilot Jet in pre-Premier carbs.)
    2 Rings – AM/622/502/17 (Equivalent to 25 Pilot Jet in pre-Premier carbs.)
    3 Rings – AM/622/502/19 (Equivalent to 30 Pilot Jet in pre-Premier carbs.)
    4 Rings – AM/622/502/21 (Equivalent to 35 Pilot Jet in pre-Premier carbs.)
    5 Rings – AM/622/502/23 (Equivalent to 40 Pilot Jet in pre-Premier carbs.)

  • Frank Del Monte

    Need chart showing Premier Pilot Jet sizes and Number of rings for each size and lean to richness for the full spectrum of jets. For example # 19 has 3 rings, does a #17 have 2 rings or 5 rings? Is a #17 leaner or richer than a #19? See below.

    For example:
    15 1 ring Leanest?
    17 2 rings
    19 3 rings
    21 4 rings
    23 5 rings Richest?
    …… Any more?

Leave a comment

Please note, comments must be approved before they are published