Easy Amal setup

Hi, new here, first post.

Amal set up - an easy way.

First thing is bike should be in good order. Ignition, valves set, no manifold or other air leaks, a clean air filter, carbs internals cleaned with unworn jets and throttle cables cleaned and oiled. The float heights should be set, I scribe a mark 2mm down in the float as a target. There is a lot of information on the web about Amals. If the provenance of your carb internals is not known change out internals, especially the needle jet as this wears the most. That's the hard part over.

Assuming all the above is done then in my humble opinion the easiest way of setting up a pair of Amals is as follows.

1. Take the carb caps off, pull the slides out. Lay the slides, springs, cap and needle assembly side by side in palm of your hand. Gently twist throttle, by doing this you should see and feel if they move at the same time. Adjust as required. Then open throttle all the way, both slides should compress the spring and stop moving (at the same time) when almost touching the carb cap. It should be apparent by visual and tactile inspection if something is out of sorts. Do all of this with assembly laid across palm of hand.

2. Dismantle one of the slide assemblies. Drop the slide into each carb in turn, adjust idle screw so that it is just touching the slide, (probably going to have to start by turning it out first). By keeping a finger on top of the slide and pushing down gently you will feel when this happens. Retrieve the slide and reassemble.

3. Assemble carbs, take care not to over tighten cap screws as this will cause the slides to stick due to distortion (this applies to all 6 fasteners on each carb, use a spring washer!). Make sure when assembled slides "snap" back from full throttle open. Check this with tank on prior to bolting tank down.

4. Pilot air screw, turn clockwise all the way, gentle seat, then turn back out 1.5 turns. Idle screws (which should have remained untouched) turn clockwise in 1.25 turns, raising the slides equally.

5. Take bike for a short run with a screw driver to hand. When warm set idle by carefully adjusting equally the idle adjust screws.
A) Set on the high side 1200 rpm thereabouts (idle screws). Adjust the pilot air screws in turn, for highest idle speed.
B) Adjust the idle screws (equally) for idle speed of 1000rpm thereabouts. Adjust pilot air screws for highest idle, then turn clockwise (richer) about 1/8th turn.
C) Adjust idle screws for idle of about 800rpm, higher if your preference. It is important not to lose track of where you are at especially with the idle screws, always adjust these both at the same time equally as you are moving the throttle slides and you want to maintain balance.

6. If you have a manometer, attach to the carbs and they should show as pretty well balanced. But at any rate can be used to fine tune.

Norton Commando Combat, 932 carbs, stay up floats, aluminium float valves, 106 needle jet, 230 main, flat top spray tube, no. 3 hard alloy slide, 2 ring needle set at mid position. No choke used, I may get round to chamfered spray tubes and 4 ring needles as an experiment. I tried 4 ring with the flat top spray tubes, kept stalling off idle when engine cold, (lean due to longer needle I think), though got a nice colour on the plugs and ran pretty good when hot. Ridden along the highways and byeways of merry Olde England. I get 57 miles to one of Her Majesty's gallons.

Hope I wasn't trying to teach grandmother to suck eggs, I just haven't seen this methodology (1 & 2, the other stuff is standard practice) described in quite a few hours of Googling although I am sure it's been done before.

Steves said:

Assuming all the above is done then in my humble opinion the easiest way of setting up a pair of Amals i
1. Take the carb caps off, pull the slides out. Lay the slides, springs, cap and needle assembly side by side in palm of your hand. Gently twist throttle, by doing this you should see and feel if they move at the same time. Adjust as required. Then open throttle all the way, both slides should compress the spring and stop moving (at the same time) when almost touching the carb cap. It should be apparent by visual and tactile inspection if something is out of sorts. Do all of this with assembly laid across palm of hand.

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If the exposed length of the two inner cables are not exactly the same length (and they're usually not), that test won't mean anything. Use tilting rods under the slides or just listen for the slides clicking shut together.

2. Dismantle one of the slide assemblies. Drop the slide into each carb in turn, adjust idle screw so that it is just touching the slide, (probably going to have to start by turning it out first). By keeping a finger on top of the slide and pushing down gently you will feel when this happens. Retrieve the slide and reassemble.

Click to expand...

No need to dismantle anything. With a screwdriver in the throttle stop screw's slot, you can feel the slide drop onto the stop screw as you close the throttle. Screw it out until you no longer feel it hit the screw.

Hi Triton, thanks. OK I thought the adjusters on the top of the carbs when adjusted correctly made the exposed cable length the same or rather corrected any difference in length. I agree I would be surprised if the cables were exactly symmetric.

I tried the screw driver trick and also thumb on one screw, finger on the other hand span contortions, to feel for slide contact. I felt happier doing it the way described, takes about 10 mins to get tank and carb tops off.

Thurso! Way up north, I worked out of Wick for awhile in the early 90's. Was having a clear out this afternoon, found a pair of shoes (cycling) that I bought in Thurso........spooky! Just seems like yesterday.

My method of synchronizing slides is to put my left thumb in one carb and forefinger in the other. Gently twist the throttle feeling when they move and adjust the cable adjusters until they start moving at the same time. Of course, the idle speed screws need to be out.

Steves said:

I tried the screw driver trick and also thumb on one screw, finger on the other hand span contortions, to feel for slide contact. I felt happier doing it the way described, takes about 10 mins to get tank and carb tops off.

Click to expand...

Different things work for different people.

Thurso! Way up north, I worked out of Wick for awhile in the early 90's. Was having a clear out this afternoon, found a pair of shoes (cycling) that I bought in Thurso........spooky! Just seems like yesterday.

Click to expand...

Been in Wick, (or Pulteney anyway), for the past 7 years but never updated profile.

You can also drop the float bowls and remove the mainjets to synchronize the slides via the now exposed needles.

If you want to sync your slides with vacuum guages or by feeling the exhaust pulses you can unscrew the idle screws and hold the slides at idle via the friction screw on the twist grip. Then after you've synchronized the slides/cables synchronize the idle screws.

The most important thing is to get the needles and needle jets right. If you lower the needles one notch from the centre position and you don't get the cough when you ride the bike when it is warm and change up and down through the gears. You are running too rich. I always fit main jets which are slightly too big when doing this test. Idle settings are a minor issue and they change with the temperature of the motor anyway. With my own bike, I still have not changed to different taper needles to find the best for my purposes. I use Mikuni needles in my 34mm MK2 Amals because there is a better range of options available. However because I normally use methanol fuel, I get away with more error than you can with petrol.