carb questions (amal)

MichaelB said:

Worth a read, if you haven't already.

Vintage Bike Magazine » Amal – A comprehensive look

vintagebikemagazine.com

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thanks for link. definitely will read it

Very informative article, and I'm more convinced now that before that it is a worn needle jet. The symptoms line up exactly with mine, and its certainly got enough miles to qualify for "worn",

Thanks again for the link.

If the pilot jet is blocked its sometimes so hard to unblock, and even using the fine wire can be a task to unblock, it only a very small passage and any crud caught in the passage will have a effect on the running, I have gone back to my old Amals after 12 years of running PWK carbs and after pulling the old Amals down and soaking all the bits in vinegar for a few days and a good clean before putting back on the bike started first kick but only running on one cylinder so another pulled down and socking and a good poke with a fine wire as well high pressure air, had my fingers over all polit holes and after hitting it with the high air pressure what was blocking the left carb shot out and hit my finger so hard it felt like someone poked me with a sharp needle.
This was after 3 pull downs and 5 days of soaking in vinegar, cleaning with carb cleaner, the wire poke and high pressure air before it finally dislodged now the Norton is running the best it ever has, it don't have to be fully blocked to make an effect on the running.
Running a Joe Hunt maggie and my old Amals my Norton has run the best it ever has, but of course electrical problems can be fuel problems and as well the other way around the good thing with the JH I don't rely on electrics to run my bike.

Ashley

MichaelB- thanks for the carb tuning link! That was very helpful!

I will note that under the “too rich condition” tuning section the very first thing listed as an issue is float level. This is one of the few things that can shift even within a perfectly clean carburetor and has a profound effect on mixture, especially at lower speeds and fuel draw. I was always taught the importance of establishing correct fuel height before attempting any fine tuning as it sets a baseline for flow characteristics within the carburetor.

Worn jets are indeed a problem too, but in my case it came down to the bowls simply being overfilled and the rich condition that caused.

Another thing with Amal carbs on Nortons is vibrations although Commandos run Isolastics the motor still vibrates through the carbs and manifolds, rubber mounting the carbs help but if your Norton is a everyday rider and clocks up the miles jets and needles will wear, from new my Norton was a everyday rider till 2013 and in the 47 years of ownership I always replace the jets and needles every 3 years without fail, with vibration to the carbs the main jets wear oval, a carb rebuild kit is cheap and should be part of replacing over time for good running.
In 47 years of ownership I have had my share of problems with electrical problems from running points, EI with 2 failing in short times but my last Boyar ran great without any problems for 31 years but had coils fail, batteries giving up the ghost to being left stranded but always manage to get home except when my first Boyar EI sh*t itself 100 miles from home back in 82, so don't discount electricals as a problems with your Norton, just have to take one step at a time and don't go to the next step till you are for sure it's not the problem.
I have manage to get home running on one cylinder from a failed coil 2x over the years of owning my Norton from new or a carb manifold coming lose at night, that was an easy fix next day lol.

Ashley

ashman said:

Another thing with Amal carbs on Nortons is vibrations although Commandos run Isolastics the motor still vibrates through the carbs and manifolds, rubber mounting the carbs help but if your Norton is a everyday rider and clocks up the miles jets and needles will wear, from new my Norton was a everyday rider till 2013 and in the 47 years of ownership I always replace the jets and needles every 3 years without fail, with vibration to the carbs the main jets wear oval, a carb rebuild kit is cheap and should be part of replacing over time for good running.
In 47 years of ownership I have had my share of problems with electrical problems from running points, EI with 2 failing in short times but my last Boyar ran great without any problems for 31 years but had coils fail, batteries giving up the ghost to being left stranded but always manage to get home except when my first Boyar EI sh*t itself 100 miles from home back in 82, so don't discount electricals as a problems with your Norton, just have to take one step at a time and don't go to the next step till you are for sure it's not the problem.
I have manage to get home running on one cylinder from a failed coil 2x over the years of owning my Norton from new or a carb manifold coming lose at night, that was an easy fix next day lol.

Ashley

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I have to admit, I never considered the needle jet.

trappnman said:

I have to admit, I never considered the needle jet.

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When I first had my 850 mk11 running after acquisition, found the bike would hiccough and mis-fire upon pulling away from stop signs etc. Was running what the bike came with...a single Amal of unknown age/abuse history, though I'd cleaned it and cleared all the jets thoroughly. Since this stuff was all new to me, first classic bike etc, I ran it into a local classic bike shop familar with nortons. They said the pilot jet was likely worn oval. Fitting a new one and the problem was gone. This was more severe in effect than what you are reporitng and was happening at just off idle throttle openings, but it could be that your jets are beginning to go out of round whereas mine was very out of round.

It's not just engine vibration that causes this wear...the high frequency pressure pulses of the intake air past the slides plays a big role...also for slide wear in the carb body bore.

The last rebuild kit's gaskets, that I got, were miss cut and interfered with the float at the pin area. Just my two cents, sorry if you already heard this

My original Amals slides wore out withing 20k miles from new they were so worn the only thing stopping them spinning was the slide pin but being broke at the time I couldn't afford new carbs but the Norton ran ok with the worn slides it only effected the idle, had to keep the throttle open to stop the bike from dying at traffic lights etc.
At 79 round abouts I joined the Norton owners club in Brisbane and they sent away for 2 new Amals for my Norton, this was the days before the internet, after a few weeks/months they turned up to find 2 left hand carbs so another 2 months or more waiting for one carb to be sent back and a right carb to be sent out, at the time was $100 for both new Amals but the time it took to get them was 6 months and that was 6 months more running worn out Amals, at the time the Norton was my only transport.
But these new Amals are still running on my Norton to this day they seem to be made out of different alloy not like the original Amals and the slides still don't show any wear but the last 12 years I was running PWK carbs from Jim as one of the Amals was playing up thinking it was time to replace before knowing about the dreaded pilot jet blockage, any way after running the PWKs for 12 years and having troubles with the left float sticking all the time I had enough even with Jim's help to resolve the sticking float problems, so ended up pulling the old Amals out from under my work bench and pulling down for cleaning and replacing all the jets and needles and to my surprise after all the years running on my Norton from 1980 to 13 years ago the slide were still good with no wear at all and over 100k miles on them, even my old Triumph mate couldn't believe it.
As was said before 3 pull downs before fixing the block polit jet circuit and the Norton is running the best it has ran in its whole life, the Joe Hunt was installed 12 years ago the same time the PWKs were installed, but the Joe Hunt and old Amals are working so well together with no misfires just runs so smooth no matter how hard I open the throttle, I run a 2S cam have major head work and larger jets in the Amals and my crank is balanced for the hard mount Featherbed frame, but my Norton has always ran well with Amal carbs and not sure why at the time why I went to the PWK carbs, well you learn by your mistakes lol.
But as I say it's always pay to replace needles and jet regularly if ridden everyday, for $40 carb kits are cheap for great running and understanding blocked polit jet passages and how to fix it.
Or maybe I just have a freak Norton as it has done me well in the 47 years of ownership and was the first bike I ever built when converting it to the Featherbed frame back in 1980 and was put back on the road 1/2 way through 1982 with the hot 850 Commando motor.

Ashley

An update..... worn needle jet symptoms fit my problems to the T, and replacing them solved the problem. Thanks for the help.