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


11 comments

  • Peter Davis

    I put a new premier 900 on my tr7v because the bore was worn out. Out of the box, I installed it and of course it ran like crap. So, I checked out the float. It was set about a 1/4in low. Bendable tangs on the new style float worked to adjust it to where it ought to be. Back on the bike, with gas going to it, I found that the tickler would bearly move the float. Moving the float down to tickle better was not working. After trying to get the carb to run right with its other apparent issues, I finnaly yanked the tickler out of this brand new amal premiere carb because it kept hanging up and I could see that it wasn’t going down enough. The flared roll pin was very poorly flared and jagged. Squeezing it in, and removing it I found the best way to extend its travel was to sand down the end of the button so it travels farther before it hits the stop. Some finess was required to make a new flare, but anything is better than the crap they passed at the factory. Tickeling is immediate now and the float is dead on.
    BUT, it sure runs different from the old Amal. When driving it, I can tell it is way more powerful and smoother. I’ve had this bike over thirty years and have put plenty of point sets in it. Of coarse I have a timing light. A few years ago I put in Boyer ignition. Tremendous improvement, better than I expected. It runs stronger than I ever thought possible with the new carb and electronic ignition.
    HOWEVER, it still has issues. The engine was overhauled 10 years ago and still has great compression. It has straight pipe hollow mufflers with one of those old time cheap little baffels stuck in the end. It has crossovers.
    The new carb was obviously running too lean at idle. I put a .021 idle jet in it, up from the stock .017, skipping the .019 because it was idling very lean. It idles strong now with the mixture screw out 1 1/2 turns out. It purrs at a low idle.
    It runs like the bat from hell, but I get a momentary bog under hard acceleration. I put all new gaskets on the intake manifold just to be sure. I experimented with the needle hight. Even though it ran fine in the middle possition, it runs throatyer it the richer position. The slide is a 3 1/2, correct for a tr7v.
    The problem is it still has a bog, as if an acceleration pump is no good, which it dosen’t have.
    I am thinking now, maybe the coils arn’t liking the compression load with the new carb. I now I replaced the coils some tme in the past wih stock new ones. Anyway, once it’s past the bog it’s on it’s way to doing 100mph with no problem. How could it be the coils? It never used to bog with the old carb.

  • Peter Davis

    I put a new premier 900 on my tr7v because the bore was worn out. Out of the box, I installed it and of course it ran like crap. So, I checked out the float. It was set about a 1/4in low. Bendable tangs on the new style float worked to adjust it to where it ought to be. Back on the bike, with gas going to it, I found that the tickler would bearly move the float. Moving the float down to tickle better was not working. After trying to get the carb to run right with its other apparent issues, I finnaly yanked the tickler out of this brand new amal premiere carb because it kept hanging up and I could see that it wasn’t going down enough. The flared roll pin was very poorly flared and jagged. Squeezing it in, and removing it I found the best way to extend its travel was to sand down the end of the button so it travels farther before it hits the stop. Some finess was required to make a new flare, but anything is better than the crap they passed at the factory. Tickeling is immediate now and the float is dead on.
    BUT, it sure runs different from the old Amal. When driving it, I can tell it is way more powerful and smoother. I’ve had this bike over thirty years and have put plenty of point sets in it. Of coarse I have a timing light. A few years ago I put in Boyer ignition. Tremendous improvement, better than I expected. It runs stronger than I ever thought possible with the new carb and electronic ignition.
    HOWEVER, it still has issues. The engine was overhauled 10 years ago and still has great compression. It has straight pipe hollow mufflers with one of those old time cheap little baffels stuck in the end. It has crossovers.
    The new carb was obviously running too lean at idle. I put a .019 idle jet in it, up from the stock .017, skipping the .018 because it was idling very lean. It idles strong now with the mixture screw out 1 1/2 turns out. It purrs at a low idle.
    It runs like the bat from hell, but I get a momentary bog under hard acceleration. I put all new gaskets on the intake manifold just to be sure. I experimented with the needle hight. Even though it ran fine in the middle possition, it runs throatyer it the richer position. The slide is a 3 1/2, correct for a tr7v.
    The problem is it still has a bog, as if an acceleration pump is no good, which it dosen’t have.
    I am thinking now, maybe the coils arn’t liking the compression load with the new carb. I now I replaced the coils some tme in the past wih stock new ones. Anyway, once it’s past the bog it’s on it’s way to doing 100mph with no problem. How could it be the coils? It never used to bog with the old carb.

  • Classic British Spares

    Amal Premier pilots have grooves on the ends

  • Mike

    How do you determine the size of the jet you have?

  • Syd

    The sweet spot is when you have a 14-1 air fuel ratio, attained by proper jetting & adjustments.

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