Amal premiers (2018)

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Aug 29, 2011
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Can anyone tell me what the removable idle jet sizes are. I have problems with it running lean so ordered new jets. My originals are ending in 19 which have 2 rings around them. I ordered 2 ending in 21 which have 4 rings on them. Now i thought the bigger the number the larger the jet , but I noticed the holes were visibly smaller. On fitting them I couldn't get it to run on the idle jets at all.
Any advise? Can I drill the new jets out and what size drill would I need ?
Thanks
Chris r
 
15,17,19,21 & 23 and are thousanths of an inch.



"2 rings" should be '17'



Premier ID Grooves
1
622/502-15
2
622/502-17
3
622/502-19
4
622/502-21
5
622/502-23
Thanks for the quick reply, but if my 21 are supposed to be larger than the 17's why are the holes smaller?
These were purchased from Rgm and in the original amal packages, sealed.
 
@blacklav sorry if I’m asking you a stupid question.

You are referring only to the hole at the end of the pilot jet?

That’s the only one that is precisely drilled - the holes in the side are not metered at all.



I think I have put this up here before, but it’s a useful reference.

Here is a mail received from Amal sometime ago when we were trying to troubleshoot the Dommie:

The brass headed screw in the position opposite to the Pilot Air Screw is the new design of pilot jet which replaces the pilot bush.
It is identifiable by the crossed slots in the head.
The attached photo shows it in position.
The jet is is intended to be screwed firmly into the carburetter.
The method of adjusting the idle is unchanged from the standard Mark 1.
(The Standard (non–Premier) carburetters now have a plated threaded plug with a single slot screwed into the same position to improve access to the bush for cleaning.)

The ID of the standard jet is 0.017”
This is the same as the nominal ID of the former pilot bush which was rated at approximately 23cc.
The new jets are also available in 15, 19, 21 and 23 sizes which again are measured in thousandths of an inch.
The graduations between the jets are smaller than the 124/026 range of pilot jets, one jet size being equivalent to approximately ¾ of a turn on the Pilot Air Screw.
The most popular alternative size so far is the 19.
Identification is by rings engraved around the nose of the jet, as listed below.

Premier ID Grooves
1 - 622/502-15
2 - 622/502-17
3 - 622/502-19
4 - 622/502-21
5 - 622/502-23

Amal premiers (2018)
 
I'm wondering why so many are switching to the 19. I checked a 17 with the drill bit I use to clean the jet on non Premier carbs. It was a perfect fit. Maybe, the air flow route through the carb is different?
 
I think the holes and routing is a bit cleaner on the newly manufactured premier carbs.

Also machined tolerances are tighter, and the slides are less rattley in the bodies.

I guess everything is a little more accurate these days than it used to be back in the pot metal age!
 
Just phoned amal, they suggest returning them for testing ( flow rate). So I'll post the results when I get them.
Thanks all.
Chris r
 
I have converted an old unworn body to Premier pilot jet and anodised slide, I went for a 17 premier pilot in place of the previous 25 which I had pressed out and then drilled and tapped the hole to take the premier pilot. It spits and farts on startup on this carbs cylinder so will be going to the 19 pilot, when warm it tunes up fine on the idle so based on using an old body it looks says to me its the new pilot configuration that causes the need to go to 19.
 
I concur with your hypothesis there Kommando.

I also think that the Premier arrangement is far more sensitive to differences. When I were a lad, I hardly ever recall changing pilot jets, and when I did, they didn’t seem to ‘transform’ anything. Main jets and air screw were at required fiddling with 90% of the time it seemed.

But recently, my T120 ran very poorly indeed on #17 pilots, changing to [HASHTAG]#19s[/HASHTAG] made a huge difference, way more than I suspect changing one size would make in old Amals.
 
Kommando, can you please post your results. My bike does the same thing, pops and bangs on start up then runs okay with 17's. Wish they were easier to get to. Looks like a carb will have to come off.
 
I just changed from 17 to 19.
Took off both bowls and managed to get a screwdriver on them.
BUT they are too long to get out with carbs attached to engine.
Loosened one carb and manged to get old ones out and new ones in.
Will fire up tomorrow. Sure hope she runs better. Not wanting to repeat process to put the 17s back in.
 
I just purged or dumped out of my wallet, $765 Can, for both carbs, including taxes and shipping. Great turn around time by the way. ordered on Friday got package on next Thursday. Regular Post (snail mail).
I got in the mail yesterday, the "New" Amal Mk1, Premier, (Alloy), Marked R29 and L30, from one of my Parts Dealers which is, BCS in Nova Scotia.
Three lines on the idle jet #19 verified for an 850. 260 mains. thumbs up! Checked!
Much Lighter (weight) than original which is very good, another thumbs up! Quite happy with over all results so far. I measured the difference on my acurate weight scale. You save 24.84 oz. on old vs new for both.
Not happy that the Fuel Banjo is not 180 degrees as it should be on any Norton 850, About 15 degrees offset on both, maybe a Triumph thing???, (not sure) but the castings on the bodies are trimmed (machined) for (tight) fit between the two carbs, aka side by side fitment. So No interference. I Still need to mount and balanced and be road tested.
Looking forward to this and will report back. Will report back on fuel economy aka Miles per Imperial gallon. Ha the rest of you convert to your metric preference. I'm old school.
Hope it is worth it.
Cheers,
Tom
 
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Not happy that the Fuel Banjo is not 180 degrees as it should be on any Norton 850, About 15 degrees offset on both, maybe a Triumph thing???,
Yes, Triumph type 150-degree banjos for 5/16" fuel pipe.


The 'Norton' banjos were originally included in the fuel line (either two single spigots in the 'H' line or two double 180s) and not listed as individual Norton parts after '1972'.

 
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I just changed from 17 to 19.
Took off both bowls and managed to get a screwdriver on them.
BUT they are too long to get out with carbs attached to engine.
Loosened one carb and manged to get old ones out and new ones in.
Will fire up tomorrow. Sure hope she runs better. Not wanting to repeat process to put the 17s back in.
This is a real pain for sure, but i know the idea of a removable jet wasn't even envisaged in 72
The idea of removable jets in situ is strong so when i next look at this i will look to see if shaving a very small amount off the head of the jet will allow entry but still enough material to drive them
When you do currently unwind them they almost come out so i don't think that much material needs removing
 
don't know where this thread is, but i'll add my 2-cents. i have new premiers on my BSA and a set for the commando - both are spec'd with #17 pilots. CORRECT ME IF I'M WRONG, but my understanding is the way the jets and adjustings screws are designed, the correct pilot jet size should be when the pilot adjusting screw is within the 1-2 turns out with an ideal setting at 1.5 turns. if the pilot screw is outside the 1-2 turn window, one should consider a different pilot jet size. i'm thinking the #17 (premier) is equivalent to the older amal #25. both my bikes are right around the 1-1/4 pilot screw turn - BSA with new premiers and #17's -- norton running original concentrics and i'm assuming #25 pilot jets.
 
i have new premiers on my BSA and a set for the commando - both are spec'd with #17 pilots. CORRECT ME IF I'M WRONG, but my understanding is the way the jets and adjustings screws are designed, the correct pilot jet size should be when the pilot adjusting screw is within the 1-2 turns out with an ideal setting at 1.5 turns.

I can't comment on your BSA but #17 can be too weak for a Commando as Burlen/Amal has been fitting #19s to Commando 850 carbs for a while now.
"We are now fitting size 19 Premier pilot jets as standard to 850cc Norton Commando carburettors as this has been found to perform better than the size 17 fitted to earlier versions of the carburettor."

norton running original concentrics and i'm assuming #25 pilot jets.

They should have the normal (0.016") pilot bushes.
 
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