Help troubleshooting kickback & stalls after starting (2016)

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Thanks LAB.

4 posts instead of 3 might be the reason I am not getting lights in Park position, when the key is turned to the left.

If anyone has the Lucas part number for the original 3 position switch, I will begin to look for one NOS.
 
I don't know if it has already been suggested,
but I think I would run a jumper wire from the brown/blue to the white (eliminate the switch completely) and see what kind of spark you get.
 
After the pilot jet has been cleaned and cleared with a stiff wire, carb cleaner and compressed air, what else would cause a no gas situation? The main jet is not plugged either.

After a lot of tickling, the bike fires both cylinders for a second, but does not run.

Bike has good spark and timing is set correctly. It's a points system.
 
I read the earlier thread and am not sure of the carbs on your bike.
Do you have the numbers on the carb sides available?
Perhaps you have very early Amal Concentrics with the short jet holder and maybe pilot jets in the bottom of the carb body.
Did you visually confirm that there are pilot jets in the pilot screw holes?
Check if your spark plugs are wet with fuel after you kick it several times.
Sounds like you are not getting fuel to the carbs properly.
 
They are Amal 930s from '71. The plugs are not wet for the amount of tickling and kicking I've done.
Plenty of spark and no kickback. Am thinking of swapping in a known set of Amals but prefer to avoid that hassle.

What else would cause 1-2 pops but no run? Tried at all throttle and choke positions. Sometimes get no pops at all. Fuel just not getting in there.
 
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Try opening both petcocks? Open the tank filler to see if you are getting a vacuum, if that works then clear the breather hole in the cap?
 
you could have one or two plugged petcocks cutting off gas flow, to test just take off the gas lines at the petcocks and open them up with a cup underneath and see if you have good flow - do you have an inline fuel filter that could also be plugged?
one last thought, you say you are running the original Amals, 45 years old that you do not know what kind of shape the slides, needles, jets, etc are in ? Seriously, fit a single 34 Mikuni all pre jetted and ready to go and get rid of the old Amals, with a much better choke and idle system you will have a better starting, idling, and running bike up to around 5000rpm, so you will lose a couple mph at the top end, who cares?
 
Thanks but I would think it should start if there is plenty of flow and fuel in the bowls. It is gushing out when the tickler is pressed.
 
elefantrider said:
After the pilot jet has been cleaned and cleared with a stiff wire, carb cleaner and compressed air, what else would cause a no gas situation? The main jet is not plugged either.

After a lot of tickling, the bike fires both cylinders for a second, but does not run.

Bike has good spark and timing is set correctly. It's a points system.
Click to expand...

This says to me that you think it is a fuel flow problem.

Easy to test though without any intrusiveness. just take off the gas lines at the petcocks and open them up with a cup underneath and see if you have good flow and if you do, test it again with the cap open. Do the same both sides, and you have either confirmed or eliminated a potential problem point.

I tried kicking over my bike for the first time after a rebuild this weekend. The petrol didnt flow enough into the lines until I opened the lid.
 
Well, I am willing to try pressurizing the tank with compressed air hose to increase flow. If that would help get more fuel into the motor to elimiate that issue.

It’s a glass tank and i don’t keep much fuel in it.
I am using the reserve side tap only and my fuel line has a balance tube. So of course the reserve side carb flows a lot more fuel when the tickler is pressed. Fuel still flows out a lot but maybe not enough pressure to enter the idle circuit?
 
Don't pressurise the tank!!! Try using a slave tank,throw the glass one away and buy a metal one
 
elefantrider said:
After the pilot jet has been cleaned and cleared with a stiff wire, carb cleaner and compressed air, what else would cause a no gas situation? The main jet is not plugged either.
Click to expand...
Pilot circuit still dirty or blocked.
elefantrider said:
After a lot of tickling, the bike fires both cylinders for a second, but does not run.
Click to expand...
Pilot circuit.
elefantrider said:
The plugs are not wet for the amount of tickling and kicking I've done
Click to expand...
Pilot circuit.
elefantrider said:
I have the pilot jet screws out about 1.5 turns, but strangely that puts them at different depths on each side.
Click to expand...
That doesn't seem right.
 
Just another small detail:
The pilot air screw and throttle stop screw are different. The pilot air is tapered and throttle stop is blunt.
Some pilot air screws may have a slightly different taper.
Suggest you remove the screws and compare tapers which may account for the different setting depths.
Also check the two tiny vertical holes downdraft from the slide in the carb body. They can only be seen with the slide removed.
There has to be a reason why fuel is not getting through he carb starting/idle circuit.
 
Thanks. I am going to pull the slides, take off the carbs and go through the pilot circuit, this time off the bike. Will try to get to it today.

May just put on my other 930 carb bodies.
 
Took apart the carbs, now very clean, and no blockage anywhere. 2 gallons gas, fuel taps both flowing great. Same problem. 1-3 fires, then nothing. The battery has a full charge but seems to drain very fast for some reason. Swapped out batteries too but same problem.

I am going to look again at the timing and electricals again. Might throw in my old Boyer this weekend. It's a powder coated frame but I even ran an auxiliary ground from the positive battery to the motor. Points gap is set to .015 and new NGK plugs to .028.

To be continued…...
 
Re; “The pilot air screw and throttle stop screw are different. The pilot air is tapered and throttle stop is blunt.”

Both should be tapered !!!

You may also have a stuck advance /retard, ignition set too far advanced......
 
Here's a photo of the difference between the pilot air screw and throttle stop screw.
I have tried to capture the slight difference in tapers and heights on the pilot air screws. Nice to get matching parts.
Help troubleshooting kickback & stalls after starting (2016)
 
Once you are stymied, go back to basics... remove the air filter and make sure both inner bodies of the carb move up and down with the twist of the throttle. Make sure both jet needles move with the carb inner bodies. There's your simple mechanical check.

If you are convinced the problem is fuel delivery because of the appearance of the plugs, that usually indicates clogged pilot jets when poor starting is the symptom. So,... prepare your normal starting proceedure as usual, except twist the throttle to half throttle and kick it over. If it fires, don't release the throttle. If it continues to run at half throttle, but will die when you release the throttle,... it's probably a clogged idle circuit, because you've now established that it wont run in the low rpms, where the idle circuit dominates.

At half throttle the influence of your needle and needle jet interaction, if assembled to spec, has corrected your mixture ratio, so the bike continues to run as long as you hold the throttle open. It's very common for a bike with a clogged idle jet to run at 3500- 4000 rpm, but break up and die at anything below 2000 rpm.

I've had this issue, and my bike had similar symptoms as yours. I eventually drilled out the backside of the amal 930 in question and cleared the idle jet from the back side. then I threaded the hole I drilled and installed a set screw with sealant. I reassembled the carbs after the surgery, and the bike that wouldn't idle or stay running, now happily ran at 1000 rpms... HTH
 
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