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John Healy's article on carb adjustment states "...you want the Pilot Air screw to end up with the a steady idle when it is 1 1/2 turns out from fully seated....".

But the Workshop Manual (page B12) states 2 1/2 turns out from fully seated. Can someone please explain this difference.

1972 TR6R Tiger 650
 

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John Healy's article on carb adjustment states "...you want the Pilot Air screw to end up with the a steady idle when it is 1 1/2 turns out from fully seated....".

But the Workshop Manual (page B12) states 2 1/2 turns out from fully seated. Can someone please explain this difference.

1972 TR6R Tiger 650
It is generally accepted that one starts at 1.5 out from being seated. Most carby's will settle into a good idle at this point give or take 1/8 turns. RR
 

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Start the motor, adjust tickover to a fast-ish (1,000+ rpm) idle.
Adjust the pilot (air/mixture) screw in and out until the engine begins to falter. (dont kill the engine)
Set it to the fastest point in between the two extremes.
Re-adjust the tickover to 1,000.
 

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It is generally accepted that one starts at 1.5 out from being seated. Most carby's will settle into a good idle at this point give or take 1/8 turns. RR
What's the reason for this? I've been wondering about it myself. Is the fuel just different enough that now the carbs are needing to be set to a richer setting? Or was it a US/UK fuel difference thing?
 

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Hi Terry,

John Healy's article on carb adjustment states "...you want the Pilot Air screw to end up with the a steady idle when it is 1 1/2 turns out from fully seated....".

But the Workshop Manual (page B12) states 2 1/2 turns out from fully seated. Can someone please explain this difference.
Colloquially known as a Meriden Misprint.

Hth.

Regards,
 

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Hi,

It is generally accepted that one starts at 1.5 out from being seated. Most carby's will settle into a good idle at this point give or take 1/8 turns. RR
What's the reason for this? I've been wondering about it myself. Is the fuel just different enough that now the carbs are needing to be set to a richer setting? Or was it a US/UK fuel difference thing?
:confused: It's a mass-produced motorcycle, consisting of thousands of parts, all microscopically-different from the ones before and after, sold all over the world, with potential ambient temperature differences of around 50 degrees C, no guarantee of standard fuel quality, etc., etc. Why wouldn't it need a range of adjustment?

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Set it to the fastest point in between the two extremes.
Basically true, but you can take it one step further. Often you will set the pilot air screw for the highest rpm to only find that the carburetor has problems transferring from the idle carburetor to the main carburetor. You can carry the tuning of the pilot air screw one step further. Often turning it in or out an 1/8, or a bit more, of a turn to improve the the transfer from one carb to the other. You do understand the concept the Amal is 2 carbs in one body?

But the Workshop Manual (page B12) states 2 1/2 turns out from fully seated. Can someone please explain this difference.
If one was to list all of the inaccuracies in the Workshop Manuals it would take hours. In the same section they recommend with twin carburetor models to remove one spark plug wire at a time to balance the carburetors. This is a hold over from the time when magnetos were used that had SAFETY AIR GAPS to prevent the internal windings of the armature from being permanently damaged. You should never remove a plug wire to balance the carburetors unless you make provisions for the plug to be grounded!!!

Actually there is a method for adjusting the pilot air screw listed in most Triumph manuals that doesn't include any recommendation about the number of turns. Use that method and you will see you end up closer to 1 1/2 than 2 1/2.

If you look up the Instruction sheet for the MKII published by IMI Amal (the real old Amal that designed these things) they clearly list the pilot air screw adjustment as 1 1/2 turns out from seated.
 

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Hi,



:confused: It's a mass-produced motorcycle, consisting of thousands of parts, all microscopically-different from the ones before and after, sold all over the world, with potential ambient temperature differences of around 50 degrees C, no guarantee of standard fuel quality, etc., etc. Why wouldn't it need a range of adjustment?

Regards,
Sure, but 1.5 turns being the de facto standard is just as likely to be unfit for wide use as 2.5 was, yet 1.5 is mentioned and known by just about everyone (at least in every Amal carb tuning thread I've read), yet the manual didn't use 1.5. I grant you that it could have been a typo, but in the event it wasn't, there certainly is a reason that they recommended 2.5 when everyone actually uses 1.5.

EDIT: But like johntioc said, it probably was a mistake. Oh well :dunno
 

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Sure, but 1.5 turns being the de facto standard is just as likely to be unfit for wide use as 2.5 was,......
In the U.S. as far as automobile carbs were concerned, I believe that for starters the pilot screw was turned outward 2 1/2 turns and then the mechanic proceeded with the final fine-tuning. Perhaps a slip!?!?
 

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What's the reason for this? I've been wondering about it myself. Is the fuel just different enough that now the carbs are needing to be set to a richer setting? Or was it a US/UK fuel difference thing?
The fact is that 1.5 outward turns from seated just happens to be a generalised starting point where air/fuel mixture is sufficiently correct to get an idle. Corky has explained exactly how to achieve the absolutely best mixture for any carby under most circumstances.

Most owners will choose the 1.5 start position and fine tune from there. I have no idea where the 2.5 comes from, and wherever that be, it is incorrect. RR :)
 

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+1; it's only a recommended starting point. The Amal tuning instructions I have clearly describe the process of tuning the carb(s) and the order in which the tuning should be done. The instructions work fine if followed.
 
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