Amal carbs and spark plugs issues and concerns

I have some old bikes all with chokes removed or never had a choke and 2 that still have their chokes in place.
The bikes without chokes are all very manageable, however the 2 that still have their chokes are a little nicer to operate from cold.
I'm thinking of reinstalling the chokes on the 650ss and BSA Super Rocket as I would like to use those bikes a bit more often. The 920 could also benefit from chokes for cold operation.
I've heard it said that if your idle circuit is set up so rich that the bike idles perfectly when stone cold, then it will be a little too rich when fully warm. It might still work, but isn't optimal. Makes sense to me. That's what a choke is for. You can set fueling up for perfect idling when warm and enrichen when cold via the choke.

Almost every vehicle ever built has some type of enriching system for cold running. It's built into modern fuel injection systems and seems to work beautifully.
But yes you can still ride/run without it if desired.



Glen
 
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arcpoint said:
Was there any trick to it or do you just follow the cables and remove accordingly?
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Apart from the cable opening in carb top to block off, the slider and its spring/guide tube are all inside the main throttle slide. You can remove it by just removing carb top and withdrawing the whole throttle slide out of the carb body, still on bike. Then withdraw choke slider assembly and replace throttle slider back in body, fit top and jobs a good 'un.

One question I've always had. Is there any benefit to perhaps filling in the opening in throttle slider where choke slider used to be? This opening is right where critical flow dynamics are happening and must create a turbulence there with nothing occupying that opening....
Should be a fairly easy process to block it off, even using the choke slide with some bonding agent (epoxy etc).
 
worntorn said:
I've heard it said that if your idle circuit is set up so rich that the bike idles perfectly when stone cold, then it will be a little too rich when fully warm
Click to expand...
It would be far too rich when fully warm. Nobody in their right mind sets it to idle perfectly when stone cold.

If you have no air slides, a cold start means using the ticklers, starting, then using the twistgrip to keep the engine running until it’s warm enough to idle.
 
Tornado said:
Is there any benefit to perhaps filling in the opening in throttle slider where choke slider used to be? This opening is right where critical flow dynamics are happening and must create a turbulence there with nothing occupying that opening....
Should be a fairly easy process to block it off,
Click to expand...

I’ve done that and there was no obvious difference to running.

Amal Mk 1.5 slides had no hole in the bottom for an air slide.
 
Tornado said:
Apart from the cable opening in carb top to block off, the slider and its spring/guide tube are all inside the main throttle slide. You can remove it by just removing carb top and withdrawing the whole throttle slide out of the carb body, still on bike. Then withdraw choke slider assembly and replace throttle slider back in body, fit top and jobs a good 'un.

One question I've always had. Is there any benefit to perhaps filling in the opening in throttle slider where choke slider used to be? This opening is right where critical flow dynamics are happening and must create a turbulence there with nothing occupying that opening....
Should be a fairly easy process to block it off, even using the choke slide with some bonding agent (epoxy etc).
Click to expand...
My mate does this on his big bore trident
 
Triton Thrasher said:
It would be far too rich when fully warm. Nobody in their right mind sets it to idle perfectly when stone cold.

If you have no air slides, a cold start means using the ticklers, starting, then using the twistgrip to keep the engine running until it’s warm enough to idle.
Click to expand...
Correct, air screws and idle speed set once warmed up. I set to 1100 rpm when fully warmed up.

Start and ride - idling is not good. However, Tri-Spark properly timed, Premier carbs in good condition and properly tuned with #19 pilot jets, will idle at about 700 until warmed up on all but the coldest days.

I don't like Nortons to sit idling, especially when warmed up and especially on the side stand.

Most people I've seen with Amal chokes put on "a little choke". In other words, no choke! Unless almost completely down, they do nothing. Once all the way down, they take away about 1/2 of the slide cutaway so assuming enough air is moving to suck the gas, they are running super rich.
 
Rode my Atlas yesterday cause it was sunny, finally over 40F, 50 in the shop. It needs the chokes to stay running at a reasonable RPM for a cold engine yet to fully circulate the oil, say, 1500RPM.

I used the chokes after thorough tickling. Kicked once then drained a pint of oil out of the sump. Kicked a second time and it fired right up. If there's any oil in the sump, I'm not strong enough to kick it over. That said, I fitted the T160 kick-start lever and it's now much easier to start and doesn't bend the shank of my boot or cause pain in my knee.

Atlas has a commando head, 9:1CR, probably original cam, an analogue Boyer, BP7ES plugs, resistor wires, chokes fitted to early Amal Mk 1 carbs which have been sleeved and have #20 idle jets, original factory air filter with oiled gauze, original silencers with holes in the ends of the baffles,
 
Ok. I just put in new plugs and turned the choke lever off. Tickled the carbs and the right one won't stop seeping gas all over the place. Am I going to have to take the Amals off just to figure this out?
 
Stuck float or leaking float bowl to cause that, depends where the fuel is coming from the gasket or the tickler.
 
The Mk2 Amals on my bike are jetted lean enough in the needle jets to get best performance. I put the chokes on when the motor is cold, start the motor and let it idle until it starts to slow, then take the chokes off. When the motor is hot, I don't need the chokes to start it. When you jet for petrol, it is difficult to jet fine enough to get best performance. However with a road bike, you would not want to jet that close to destruction anyway. Modern bikes do it with engine management systems - it is probably the main reason they are faster when engine capacities are similar. Most of them also have 6 speed gearboxes. Spark plugs do not matter so much when you do not run the motor close to the extremes.
I usually set the idle when the motor is hot, so it is lean when the motor is cold,
 
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Try a gentle tap with a screwdriver handle, on the float bowl, before stripping down. It may get the float to drop into the right position.

I had a sticky float. Turned out to be the replacement brass spindle the float is attached by. The brand new spindle had a small nodule on one end that was catching. I filed it off and never looked back.
 
I suggest an 850 Commando with an EMS and 6 speed box would be very quick, without doing anything else.
 
If the tapping of the bowl don't work then take the bowl off it only takes a little bit of crud to stop the float needle from seating, bit of dried up old fuel, has the bike been sitting for anytime, its only something simple to fix, Amals are a lot easier to work on than any other carb and all carbs can have this problem.
 
arcpoint said:
It's coming from the tickler rod
Click to expand...
Likely a stuck or poorly sealing float needle/seat issue...which would send fuel up out the tickler and likely flood the engine if not cleared quickly.

You can remove the float bowl without taking whole carb off...just remove the fuel line connections and remove the two small screws underside of bowl up into carb body. Drops away, hopefully with gasket in tact. The bowl, float, flost spindle, float needle and gasket should all be free. The Needle seat is down inside a boring in the bowl. Good idea to run a bit of metal polish (Autosol etc) on a q-tip in a drill chuck in the needle seat to get it nice and shiny. The latest needles are alloy with the Viton rubber tip, older style heavier brass needle & tip.
You can also inspect/test the float for any signs of leakage. Older type are a light coloured, hollow plastic that sometimes degrades (Ethanol fuel???) or just cracks and takes on fuel, making it sink and hold needle valve open...giving you signs of leaking out tickler. Newer floats are called StayUp type, made of black plastic (think they are some type of foam filled, not hollow).

Another you need to check is float level, or better yet, fuel level at point of needle closure. Can be done on bench with some fuel into bowl hose barb, holding float spindle in place nad keeping bowl flange level. Check the Amal carb setup guide docs, Bushman's Amal Tuning guide for best guidance on how to adjust/set this.

Finally, sometimes the gasket itself can cause the float to stick needle valve open/or closed due to slight interference with the float tangs along the spindle hinge area. Some folks trim the gasket a little in this area.
 
Tornado said:
Likely a stuck or poorly sealing float needle/seat issue...which would send fuel up out the tickler and likely flood the engine if not cleared quickly.

You can remove the float bowl without taking whole carb off...just remove the fuel line connections and remove the two small screws underside of bowl up into carb body. Drops away, hopefully with gasket in tact. The bowl, float, flost spindle, float needle and gasket should all be free. The Needle seat is down inside a boring in the bowl. Good idea to run a bit of metal polish (Autosol etc) on a q-tip in a drill chuck in the needle seat to get it nice and shiny. The latest needles are alloy with the Viton rubber tip, older style heavier brass needle & tip.
You can also inspect/test the float for any signs of leakage. Older type are a light coloured, hollow plastic that sometimes degrades (Ethanol fuel???) or just cracks and takes on fuel, making it sink and hold needle valve open...giving you signs of leaking out tickler. Newer floats are called StayUp type, made of black plastic (think they are some type of foam filled, not hollow).

Another you need to check is float level, or better yet, fuel level at point of needle closure. Can be done on bench with some fuel into bowl hose barb, holding float spindle in place nad keeping bowl flange level. Check the Amal carb setup guide docs, Bushman's Amal Tuning guide for best guidance on how to adjust/set this.

Finally, sometimes the gasket itself can cause the float to stick needle valve open/or closed due to slight interference with the float tangs along the spindle hinge area. Some folks trim the gasket a little in this area.
Click to expand...
Went to take of float bowl of right carb only as it's the one leaking. It appears I must have two left side carbs because the bolts are the same pattern as the left carb which on that side are easy to reach but on the right side the one screw on enough I will never be able to get back in and I have medium to smaller hands. But they have a connecting tube so did they not change the bowl mounting configuration on these, right and left? If not, they should have. If so, I have two left side carbs and not sure how I feel about that.
 
If you had 2 left side Amals you will have the ticklers on the same side and the tickler be in between both carbs on the right side, undo the fuel hose bolt to the carbs makes it easy to get to the screws.
 
ashman said:
If you had 2 left side Amals you will have the ticklers on the same side and the tickler be in between both carbs on the right side, undo the fuel hose bolt to the carbs makes it easy to get to the screws.
Click to expand...
Ok, took off the right carb bowl and the hollow float is full of gas. Def the issue. Curiously, the base of the tickle plunger rod that flares out is jagged. Not sure if an issue or just sloppy manufacturing because it doesn't matter.
 

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