Amal carbs and spark plugs issues and concerns

ludwig said:

Exactly.
The float is pushed up by the fluid till the needle shuts off the flow.
The upward pressure on the float is equal to the weight of the displaced volume of liquid.
Fuel is considerably lighter than water : 0.72 to 1.
To create the same amount of lift (and shut off the flow), more fuel than water has to go into the bowl.
If you use water to set the fluid level 5mm below the top of the bowl, then the fuel ( not the float) will inevitably rise above the water mark . About 2.5mm IIRC, and set the fuel level well above the recommended limit of 4mm.

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I'm working with another Senior Field Service Engineer this week. Yesterday at lunch he was mentioning he worked for Carter carburetor in a former job. He explained how the testing went. They had a special test solvent that was the same viscosity and same specific gravity as gasoline (but far less explosive) that they tested every carburetor with. That is, before they transitioned to batch sampling testing.

Re to choke or not to choke-
I have a driveway gate that requires a button push to close, also one to open when I forget to open it before firing the bike up.
With no choke bikes
-Start bike, lots of throttle action to keep it going, ride down to gate.
-Try to keep bike going while fumbling for gate clicker. Usually it dies.
Open gate and restart bike.
Lots of revving gets bike thru the gate but now it dies again as I click gate shut.
Restart bike again, lots of throttle action and you are off.

Bikes with chokes

Start bike with choke on full
It idles smoothly at about 1000 rpm. Pull choke off slightly.
Ride down to gate. No need to faff about with the throttle to keep it going, it runs smoothly at low rpm and takes throttle perfectly.
Open gate, ride thru shut gate, no restart needed as idle is smooth and strong. Ride away without need for handfuls of throttle and herky jerky operation.
About a mile or two down the road pull the chokes off completely.

Glen

There are so many variables that come in to play its easy to understand why one owner can punch their Estart button and have their choke free engine idle right up while other engines require choking of some form. Nature of the beast, sort of.
Neither is "right" or "wrong" but rather what's the best setting to get the damn thing running the way you want.

Regarding float level: Am I dreaming or did someone come up with a sight glass affair that you screw into the drain bung on the bottom of the Amal float? Anyone know where to get such a device?

Thomasa said:

Regarding float level: Am I dreaming or did someone come up with a sight glass affair that you screw into the drain bung on the bottom of the Amal float? Anyone know where to get such a device?

Click to expand...

AN

worntorn said:

Re to choke or not to choke-
I have a driveway gate that requires a button push to close, also one to open when I forget to open it before firing the bike up.
With no choke bikes
-Start bike, lots of throttle action to keep it going, ride down to gate.
-Try to keep bike going while fumbling for gate clicker. Usually it dies.
Open gate and restart bike.
Lots of revving gets bike thru the gate but now it dies again as I click gate shut.
Restart bike again, lots of throttle action and you are off.

Bikes with chokes

Start bike with choke on full
It idles smoothly at about 1000 rpm. Pull choke off slightly.
Ride down to gate. No need to faff about with the throttle to keep it going, it runs smoothly at low rpm and takes throttle perfectly.
Open gate, ride thru shut gate, no restart needed as idle is smooth and strong. Ride away without need for handfuls of throttle and herky jerky operation.
About a mile or two down the road pull the chokes off completely.

Glen

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You should fit an AutoSwitch to a spare clicker.
I had one on my Bonneville. I had it sensing the high beam toggle. When i need gate opening, just hit high beam for a second or two until the AS led flashed green. Highbeam off, gate opens. Life's good.

concours said:

I'm working with another Senior Field Service Engineer this week. Yesterday at lunch he was mentioning he worked for Carter carburetor in a former job. He explained how the testing went. They had a special test solvent that was the same viscosity and same specific gravity as gasoline (but far less explosive) that they tested every carburetor with. That is, before they transitioned to batch sampling testing.

Click to expand...

I just received a replacement float. The previous float was set fine so all I should need to do is put the new one in right? I'm using the same old style hollow floats. I am not sure I understand the need to make any readjustments to it. Also not even sure how to adjust it in the first place. I get all the floating shit off principles but still a newbie at this.

arcpoint said:

I am not sure I understand the need to make any readjustments to it. Also not even sure how to adjust it in the first place.

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White floats.

StayUp floats.

annajeannette said:

norton twins the fuels have changed now being made has planet based fuels, so you all need to change your spark plugs to the muliti electroids ones, all information on this is at www.greensparkplugs.co.uk. like I now use the new champion N9bcy has the same heat range as the old N5c has I am running with a single carburettor set up, instead of the twin carb set up that was on the bike from new, for a twin carburettor set up, use champion N7bcy has the same heat range as the old N4 these are 3 point elctroids and give better shelding againast ethernol fuels this is what modern petrol cars have fitted hope this may help

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Multiple ground electrode spark plugs are now considered obsolete. See this article https://www.autolite.com/docs/defau...-plugs/understanding-mge-spark-plugs-2017.pdf

Thomasa said:

Regarding float level: Am I dreaming or did someone come up with a sight glass affair that you screw into the drain bung on the bottom of the Amal float? Anyone know where to get such a device?

Click to expand...

I made one from an old plastic carb bowl drain cap, a spigot into it, and bit of clear tube stapped up along side of carb. Open fuel tap, see fuel rise until fload closes its needle, check where fuel in clear tube rises to against float bowl/carb body gasket. Compare to spec found on Burlen website.

worntorn said:

Re to choke or not to choke-
I have a driveway gate that requires a button push to close, also one to open when I forget to open it before firing the bike up.
With no choke bikes
-Start bike, lots of throttle action to keep it going, ride down to gate.
-Try to keep bike going while fumbling for gate clicker. Usually it dies.
Open gate and restart bike.
Lots of revving gets bike thru the gate but now it dies again as I click gate shut.
Restart bike again, lots of throttle action and you are off.

Bikes with chokes

Start bike with choke on full
It idles smoothly at about 1000 rpm. Pull choke off slightly.
Ride down to gate. No need to faff about with the throttle to keep it going, it runs smoothly at low rpm and takes throttle perfectly.
Open gate, ride thru shut gate, no restart needed as idle is smooth and strong. Ride away without need for handfuls of throttle and herky jerky operation.
About a mile or two down the road pull the chokes off completely.

Glen

Click to expand...

Yes. I'm of the same mind for slightly different reasons.

I have one of the earlier sets of Premiers on my Mk11 Roadster.

When I got them they were fitted with the 17 pilot jets which I changed to 19s. . The matched pair also had a 200 main jet on one side and 260 on the other. . Also had to clean out swarf and reset the float heights.

I removed the chokes mostly because the new cables I bought had a nipple pull off. I was having a fun time beleive me.

But these carbs were very very hard to transition off the idle to low speed circuit when the engine was stone cold. Time and time again you would open the throttle off idle and the engine would splutter and cut out. And if you richen it up on the airscrew to cure it the bike would not idle below about 1500 rpm when fully warmed up

Then I refitted the choke and refurbished the lever so it actually worked and stayed where you wanted it set. Now the bike starts perfectly from stone cold with the choke. Drives away with no splutter or hesitation. Take the choke off after 2 km or so and the bike always settles back to a perfect idle when hot..

When I was young I never trusted my old carbs at a traffic light and kept the revs high. Now it sits and idles as stable as a Toyota.

Ok, so I got the new NOS float in and the carbs back together without adjusting the float level (still a mystery to me) and went from the PO's Champion RN9YC plugs at .030" gaps to NGK BPR7ES plugs at .025" in an effort to make it run less rich and less hot. When that was popping too much on a test run on strong downshifting I went back to new Champions that the PO was using and gapped them at .025. Ran better but still had some popping on mid to higher RPM downshifts 4th to 3rd and 3rd to second. If I can get this worked out I think I'm good to go for a while. Should I go back to the wider gap or an even tighter gap or try the Champion RN7YC with a gap in what range? I have a recent Boyer electronic ignition and a choke but so far unused. The previous owner also didn't use the choke.

Popping on down shift is very commonly due to an airleak in the exhaust. Especially the headers.

Can also be a leak in the inlet manifold.

Ok I'm quite happy to be shot down in flames here
But has anyone noticed any appreciable difference when adjusting float height on Amal concentrics?
I've played with adjusting float height in the past but have never noticed a difference
Maybe it's just me
But as long as the float isn't too high and flooding
Or way too low I can't honestly say I've noticed a difference?

arcpoint said:

popping too much on a test run on strong downshifting…. …

Click to expand...

arcpoint said:

popping on mid to higher RPM downshifts

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What is “strong downshifting?”

Under what throttle and rpm conditions does popping occur?

Is it the exhaust that is popping, or the intake?

baz said:

Ok I'm quite happy to be shot down in flames here
But has anyone noticed any appreciable difference when adjusting float height on Amal concentrics?
I've played with adjusting float height in the past but have never noticed a difference
Maybe it's just me
But as long as the float isn't too high and flooding
Or way too low I can't honestly say I've noticed a difference?

Click to expand...

My experience is similar to yours.

Although- a fuel level set low can restrict the opening of the float valve and thus restrict the fuel supply.

Amal concentrics are very forgiving regarding fuel level.
But it is my experience that a high level helps to reduce the symptoms that worntorn describes when cold starting without choke, like less risk of stalling after initial start up.

baz said:

Ok I'm quite happy to be shot down in flames here
But has anyone noticed any appreciable difference when adjusting float height on Amal concentrics?
I've played with adjusting float height in the past but have never noticed a difference
Maybe it's just me
But as long as the float isn't too high and flooding
Or way too low I can't honestly say I've noticed a difference?

Click to expand...

Same. I've stopped fussing about with fuel levels and just set them so they don't overflow and flood similarly with the tickler.

baz said:

Ok I'm quite happy to be shot down in flames here
But has anyone noticed any appreciable difference when adjusting float height on Amal concentrics?
I've played with adjusting float height in the past but have never noticed a difference
Maybe it's just me
But as long as the float isn't too high and flooding
Or way too low I can't honestly say I've noticed a difference?

Click to expand...

"The Emporers New Clothes"

Like you, I have observed a very wide window of acceptability.

baz said:

Ok I'm quite happy to be shot down in flames here
But has anyone noticed any appreciable difference when adjusting float height on Amal concentrics?
I've played with adjusting float height in the past but have never noticed a difference
Maybe it's just me
But as long as the float isn't too high and flooding
Or way too low I can't honestly say I've noticed a difference?

Click to expand...

Amal says: "Although the Concentric carburetter will function across a wide range of fuel levels, an accurate fuel level is the foundation of the overall jetting of the carburetter and makes a significant contribution to the smoothness and performance of an engine"

Within reason, I agree with you. For one thing, the fuel level is specified the same for all MK1 concentric carbs no matter the mounting angle. Since Norton carbs tilt, the level at the rear of the carb is lower than specified. So, having the overall level low means the rear is quite low and at idle, the pilot circuit fuel suction at the rear of the carb is important. At 1/4 throttle and beyond, it probably makes no "seat of the pants" difference whatever.

IMHO:
1) With dual carbs, the fuel level being the same is more important than the actual level.
2) With single or dual carbs, the fuel level should be as high as possible without the possibility of flooding.