1974 850 Roadster: Amal Premier Carbs? (2018)

The pilot jets are the cross headed screw on the opposite side of the carb than the air screw. You will have to remove one carb to access them. Once you remove them look at the rings on nose of the jet.
https://www.britishmotorcycleparts.co.nz/amal-premier-pilot-jets

N0rt0nelectr@
A good place to start regarding popping in the exhaust, (usually indicating a lean mix) and assuming the engine is in good condition with no exhaust header leaks, valve clearances and ignition set to spec, is to check for air leaks.
Start at the carb intake insulators between the manifolds and head, then the carb manifold O ring joint.
You can sometimes see discoloration from a leak here if your parts are clean, mine did at the insulators, until removed and sealed with Hylomar.

Next would be to check the Stayup float heights are parallel as supplied or slightly lower at the front, then reassemble and adjust the pilot mixture on each side to the best setting the engine likes.
Don,t be surprised if both sides are different on either float heights or pilot settings to get the best running, mine are.

If it still pops around town and on the overun, your slides are probably too large and you need to go down a size, say from 3.5 to 3.0 as I had to when my perfectly set carbs in the 30c + euro summer stared popping as temps dropped.

A change to a spare set of £££££ anodised 3.0 slides gives perfect winter running but carbs need to be re synched and pilot mixture redone. I,ll leave these in during summer if fuel consumption and power are good.

MexicoMike
profound apologies, bronze statue looked like a healthy west coast suntan on a seasoned old school fighter that,s all...
Keep us posted on your velocity stacks and Premiers always something of interest to learn from different peoples setups.

Dutch said:

That's a good place to start ---

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Reading about old Amal's that say that the pilot jets in the factory set up carbs were #20's so 17's would look to be a bit lean. I have ordered 2 - 19's and dug out 2 new 220 main jets as were called for in the original carbs. Now I wait for my care package to arrive later in the week. Thanks for your input.
John in Texas

L.A.B. said:

http://amalcarb.co.uk/news/

"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."

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I confirmed with Amal that this is only the 850 carbs as written and I've told them that I think at a minimum that all 932 should include 19s. When you consider that the original MKI concentrics had 20s which was later changed to a "bush" still of the same size, going to 17 seems wrong. When ordering directly from Amal, you can specify the jets at no additional cost. However, when you order from someone else, that's a different matter -- the premier pilot jets are not cheap so expecting them to be changed for free is wrong. Hopefully resellers will start ordering from Amal with 19s so this issue will go away.

marshg246 said:

I confirmed with Amal that this is only the 850 carbs as written and I've told them that I think at a minimum that all 932 should include 19s. When you consider that the original MKI concentrics had 20s which was later changed to a "bush" still of the same size, going to 17 seems wrong. When ordering directly from Amal, you can specify the jets at no additional cost. However, when you order from someone else, that's a different matter -- the premier pilot jets are not cheap so expecting them to be changed for free is wrong. Hopefully resellers will start ordering from Amal with 19s so this issue will go away.

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I ordered the Premiers yesterday (Saturday) from CBS. Sent an email ahead of time to see if #19 pilot jets could be swapped for the 17's--no problem at all, and carbs shipped within an hour or so of the order (No additional charge for the jet swap). I will do as others here have suggested to take the carbs down and verify component specs, float levels, and check drillways for swarf and other foreign material--just to be on the safe side.


Thanks!

~998cc

KiwiNeill said:

MexicoMike and Fast Eddie
I removed the ticklers start of the year and the bike e starts on full choke only and #17 pilots, cranking over a little longer in minus 4c /24.8f last week but anything above 5c / 41f it fires up straightaway.
My bike sits outside under a cover while I,m still using it for work so no warm garage, just ambient autumn temps. Fired it up outside just now at 7c/ 45f no problems at all. Real world scenario, no theory involved.

If you are in the California/ Mexico corridor, you should not need ticklers at all unless you,re wintering in the Sierra Nevadas, but you,re on the right track to try just the slides first.
The jetting on my carbs also performed well at over 7000 ft crossing the Alps in August, fuel consumption average the same as lower down. I think Premiers are great, can,t all be due to the efficient Fullauto head...

I like the velocity stack look too, will sort out a filtered setup for the Premiers over winter.

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Yup, experience trumps theory there!

Just out of interest, how did you remove the ticklers, what did you do with the hole?

good question. the float bowl MUST be vented to atmosphere somewhere.

Fast Eddie said:

Just out of interest, how did you remove the ticklers, what did you do with the hole?

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Fast Eddie
I just used a small adjustable spanner under the alloy button and lightly tapped it up. No damage if done carefully.
Put stainless button headed socaps in the holes with fuel proof jointing compound to keep it in.That way you can always reinstall the ticklers.
The small alloy tickler bush sticking up can also be used to run a breather vent tube a la Japanese carbs/Amal Mk2, run them up and drop down between the carbs.

bill
you are correct, I drilled the inner blank tickler castings 4mm through to float chamber, bonded in 4mm brass tube stubs, then ran tubing as above.
Only reason I did it this way was to keep an uncluttered look but using the existing stubs with tube an easier option.
I was having problems with occasional starvation-like problems, one carb stuttering momentarily then OK.
Seemed the only venting was via the tickler tension pin slots, and mine had rust and crud so copied the Mikuni Amal type vent.
It may be a coincidence but no more problems of that sort since.

Just Dyno'd a set of 850 carbs with 19 pilots - a little rich on tickover but once of the throttle stop, perfect and linear right through to 6200rpm.

Madnorton said:

Just Dyno'd a set of 850 carbs with 19 pilots - a little rich on tickover but once of the throttle stop, perfect and linear right through to 6200rpm.

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Seeing that the pilot jets control idle only you may want to try 17's.

I see I am not the only one to need the 19 pilots, both 750 and 850. also, try 107 needle jets just to see what happens. Quite often it's an improvement. My big question is what the correct main jet is, considering the pilot and needle jet got richened. Most of us are never in the main jet range so I guess by increasing it two numbers over book settings.

Dutch said:

Seeing that the pilot jets control idle only you may want to try 17's.

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I still have room to move with the 19's, as the tickover was a little low which most probably did not help. I find the advantage that the 19's have is coming through and off the pilot circuit, proven on the dyno as the throttle could be cracked cracked open from low revs and a decent curve established at far lower revs than the Commando we had tested a few months ago.

Madnorton said:

I still have room to move with the 19's, as the tickover was a little low which most probably did not help. I find the advantage that the 19's have is coming through and off the pilot circuit, proven on the dyno as the throttle could be cracked cracked open from low revs and a decent curve established at far lower revs than the Commando we had tested a few months ago.

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That’s similar to my experience, albeit in a ‘68 Bonnie. With #17s the idle was actually good, probably aided by the idle improvement function of the Tri Spark, it was the initial just off idle that was weak enough to make for very bad running. Being ‘just off idle’ I suspected the slide cutaway, but chances to the #19s after hearing about t’other doing so, and it cured this in an instant.

I know the tuning guides tell us which part of the carb effects fueling at which throttle openings, but there is clearly an overlap that we should not overlook.

Dutch said:

Seeing that the pilot jets control idle only you may want to try 17's.

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The pilot a/f circuit has been referred to as a separate carburetor; from when the engine is idling with the throttle on its stop to somewhere about 1/4 slide movement the pilot circuit is your carburetor. Beyond 1/4 throttle the needle, the slide cutaway, the needle jet, and, ultimately, the main jet join the "team", but once above 1/4 throttle the pilot circuit is all in. If your pilot circuit is too lean that leanness will follow the mixture, to a somewhat decreasing degree, right to red-line.

The adjustments for trimming the pilot circuit (air screw and slide height) don't get the respect they deserve. In my experience it is easier to lean a Premier with a #19 idle jet then to richen same with a #17. As a good general guide: at the factory recommended idle tick-over, when at OT, if the air screw is below 1 turn out; try a larger idle jet. Conversely, if the air screw is out more then 2, 3/4 turns a smaller idle jet should be tried.

I have the new Premiers on my 850 that I put the #19 low speed jets in.My problem is that the right side pops between 1500-3000 rpm.I have checked everything trying to find out why.It sounds like an air leak but cannot find one.The carbs have been off multiple times and everything looks good.The bike idles nicely,revs up fine and after a good run,the plugs look the same.I have tested the ignition,compression,valve lash,plug wires,etc.Is there a passage in the carb that would have something to do with this as I do not know what to check next or any suggestions?
Thanks

YING said:

I have the new Premiers on my 850 that I put the #19 low speed jets in.My problem is that the right side pops between 1500-3000 rpm.I have checked everything trying to find out why.It sounds like an air leak but cannot find one.The carbs have been off multiple times and everything looks good.The bike idles nicely,revs up fine and after a good run,the plugs look the same.I have tested the ignition,compression,valve lash,plug wires,etc.Is there a passage in the carb that would have something to do with this as I do not know what to check next or any suggestions?
Thanks

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Have you tried moving the pilot jets to the other carb and seeing if the problem follows the jet?

I just replaced both the pilot jets.Same problem.Any other ideas?This is driving me nuts

YING
Have you checked the right side float level is not too low? Usually supplied with both floats parallel to bowl flange.
Also try blowing through tickler with bowl removed to make sure it,s not clogged, it vents the carb bowl, this is a problem I had at one point, same symptons as yours.
Another possible cause is airlock in the fuel line, open the reserve as well.

I practically rebuilt my motor chasing this problem having checked the new premiers had the right jets and needles in the first instance. Finally I found that although the needles were marked up both correctly, one had a slightly different taper than the other when compared side by side. Put a needle in out of my old carbs, problem solved. Quality control my arse!