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New carb cable, new problems.. #770352 04/07/19 1:27 am
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dr.ona Offline OP
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Hey Gang,
I installed a new longer cable on my carb, and now the bike wants to stall out when coming to a stop.
Previous to cable install, bike has been running great with no issues.
The carb is a new AMAL 626.

I removed the carb and checked for plugged jets, dirt etc etc.. nothing, the carb was spotless.

When I let the bike idle, it's fine for a minute or so and then all the sudden it dies and a couple seconds after that, fuel spits out of the opening.

Any ideas as to what could be causing this?
Basically if I let it idle in driveway, it dies after a couple minutes and coughs up fuel.
If riding, it wants to die when coming to a stop and idles all weird.

Thanks!

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Re: New carb cable, new problems.. [Re: dr.ona] #770354 04/07/19 1:34 am
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dr.ona Offline OP
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Also, do you think this could be electrical related?
Maybe pulling out the old cables and installing the new ones bumped something around the coils?

Bike starts on first kick and plugs look perfect.
Fresh non ethanol fuel used only.

Re: New carb cable, new problems.. [Re: dr.ona] #770381 04/07/19 12:41 pm
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Originally Posted by dr.ona
Hey Gang,
.......The carb is a new AMAL 626. I removed the carb and checked for plugged jets, dirt etc etc.. nothing, the carb was spotless.

When I let the bike idle, it's fine for a minute or so and then all the sudden it dies and a couple seconds after that, fuel spits out of the opening.......Basically if I let it idle in driveway, it dies after a couple minutes and coughs up fuel. If riding, it wants to die when coming to a stop and idles all weird.

Thanks!


Interesting! From the fact that you fitted a single AMAL 626 carb I'm guessing that you have a T100 or maybe a T100R converted to single carb? My T100T has had a similar problem with its twin carbs ever since I bought it last year. Despite clean carb internals, new stay-up floats, aluminium float needles, actual fuel level check externally with a manometer tube, I can't seem to get the idle mixture 'just so'. It idles fine when cold but gets worse as it warms up and has a random stall at times if you don't keep the revs above about 1400 rpm. It spits back when it stalls but I have not seen fuel spitting out as I have air cleaners fitted. I'm still working through this one.

It DID have electrical problems when I first got it as the ignition switch (probably original) was intermittent if you touched the key and must have been affected by engine vibration at times. Replacing that seemed to cure the random stall when stopping at junctions etc.

HTH, Brian

Last edited by Stanier8F; 04/07/19 12:42 pm.

Current bike: 1969 Daytona
Previous bikes: '62 Bonnie, '67 Bonnie, '69 Bonnie, '70 BSA Lightning, '71 Bonnie, '73 Honda 500-4
Re: New carb cable, new problems.. [Re: dr.ona] #770383 04/07/19 1:05 pm
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Put the old cable back on to see if it helps?
Did you follow the correct t procedure?

Re: New carb cable, new problems.. [Re: dr.ona] #770388 04/07/19 2:09 pm
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"When I let the bike idle, it's fine for a minute or so and then all the sudden it dies and a couple seconds after that, fuel spits out of the opening."

Could be fuel boiling in the carb, is an insulating spacer fitted between carb and manifold,?

Could also be a poorly adjusted pilot air screw.
Air cooled bikes dont like idling for long periods, they get very hot with no air flow.


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Re: New carb cable, new problems.. [Re: dr.ona] #770393 04/07/19 3:44 pm
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dr.ona Offline OP
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Thanks for the comments guys..
Yes it's a 68 T100R with single carb.
I ended up getting a new AMAL carb last Summer cause no matter how much fiddling with the old one, I had issues.
New carb solved it right away and was running perfect before cable change.

The insulated spacer is there. I never touched anything other than taking the top of the carb off to install new cable.
No air leaks and I didn't tighten anything too tight.

I'm not certain by correct procedure on replacing cable.
I have new taller bars, so I can't put the old cables back on.

I'll be back in town Monday and see if I can see any electrical mishaps under the tank.
Then I'll do another complete carb clean.

I agree about the long idilng.. but as I was rolling to a stop, the bike would spudder and want to die which it has done before.

Thanks again everyone!

Re: New carb cable, new problems.. [Re: dr.ona] #770399 04/07/19 4:53 pm
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...hello,
could be a bad synchronizing between the air screw and the slide screw or not the right float level. Do you have a good read in low RPMs in the plugs?

Re: New carb cable, new problems.. [Re: dr.ona] #770401 04/07/19 5:34 pm
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If the bike behaved flawlessly with the original cable, and all you did was install the new one to result in this new & odd behaviour, it strongly suggests a difference in cable slack between the 2 situations, or possibly the cable is not returning the slide freely to the stop screw. Maybe the cable is too tightly tied or bent?

Re: New carb cable, new problems.. [Re: dr.ona] #770402 04/07/19 5:36 pm
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1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: New carb cable, new problems.. [Re: dr.ona] #770419 04/07/19 8:10 pm
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Sounds like you may have messed up with the spring and needle clip, so the clip sits up in the spring somewhere.
I can happen and I've certainly done it. It creates an over-rich condition as you would expect, and the symptoms can be as you describe.

Re: New carb cable, new problems.. [Re: dr.ona] #770427 04/07/19 9:20 pm
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You did put the slide in the right way around?
Apparently it's possible because someone on a forum did it a year or so back

Re: New carb cable, new problems.. [Re: dr.ona] #770428 04/07/19 9:36 pm
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Unless its upside down, how is that possible?

Re: New carb cable, new problems.. [Re: dr.ona] #770498 04/08/19 4:14 pm
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No idea but it was backwards apparently

Re: New carb cable, new problems.. [Re: dr.ona] #770531 04/08/19 11:07 pm
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dr.ona Offline OP
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Thank again everyone!
Slide is in correct.. cable/clip is not mixed up with the sping.
No kinks in the new cable.. tried both with no slack and a little bit of slack in the throttle adjuster.

Also cleaned the carb again today. The carb is spotless and still looks new.
The airfuel is 2 turns out.
I see the slide moving all the way to the bottom and top smoothly.

Just took it for another small ride and same thing.. starts up perfect on one kick.
Idles great for a few minutes and then kinda sounds like it wants to die.
Sometimes coming to a stop it wants to die.

Frustrating to say the least, but I do appreciate all the suggestions.
You all are very helpful!

With my experience I almost think that it's an idle jet/circuit plugged or shitty fuel kinda thing.
It's raining here again so I'll wait couple days to mess around some more.

Re: New carb cable, new problems.. [Re: dr.ona] #770534 04/08/19 11:23 pm
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If the pilot jet was blocked it would be hard to start, or not start at all.

It is impossible to put the slide in wrong way around. If it was put in upside down the venturi would be totally open and the bike would not start.

Besides knocking a coil wire connector under tank, or such, it has to be the needle. When installing the slide while the carb on the bike is so, hard to get the needle into the needle jet without upsetting it. Besides pushing the whole thing up, clip and all, into the spring you can push the needle clip out of the groove and push it down the needle.

My rule in these cases is "what was the last thing I did!".


Re: New carb cable, new problems.. [Re: dr.ona] #770538 04/08/19 11:36 pm
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Two turns out is a very weak setting,, have you tried it with 1.5 or thereabouts? How did you arrive at 2 tuns out?


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Re: New carb cable, new problems.. [Re: dr.ona] #770539 04/08/19 11:47 pm
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OK doc, I've just one more "last chance saloon" thought.
As the issue only seems to concern the idle circuit, that it tends to idle for a short while before stalling suggests that the idle jet isn't blocked (and you've checked this thoroughly anyway).
By the way, the airscrew would usually be closer to 1.5 complete turns out. Can you experiment with that, and even less to see what difference it makes?
Keep in mind that meaningful tests must be with a warmed up engine.

But you have had the carb off the manifold a few times by now, and you've also had the bowl off a few times.
It is just possible that these surfaces are less than flat after repeated tightenings.

An air leak at the carb to manifold will present worst at idle (throttle closed) because of the high vacuum on that side of the slide.
For trial purposes, can you use a goo to guarantee a seal between all surfaces at this joint, and see if it makes any difference?

An air leak at the bowl to body, in the region where the fuel is drawn from the bottom of the bowl into the body (via the gasket) can allow idling for a short time, until the fuel already in the body line is used, but no more fuel will be drawn from the bottom of the bowl.
Again for trial purposes, try a smear of goo to ensure this avenue is sealed, and see if it makes any difference?

Re: New carb cable, new problems.. [Re: dr.ona] #770544 04/09/19 1:25 am
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Drona, You said you checked for "plugged jets". Exactly which jets did you check and how did you check them and when did you check them?

New amals are known to have machining swarf in new carburetors.

Re: New carb cable, new problems.. [Re: dr.ona] #770592 04/09/19 2:04 pm
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dr.ona Offline OP
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Thank you again everyone!
I will experiment later today after work.

The two turns out seemed to be the sweet spot for running all last year and this year.
I will try 1.5+/- turns out after a good warm up.

I'll also check for leaks.
I cleaned the jets/stack by small guitar wire, carb cleaner and compressed air,

I "think" I have a new needle and clip.. will install that too if so.
I'll also triple check wires coming loose from under the tank.

One thing I'm wondering..
Why would it idle great for a few minutes, and then all the sudden just quickly die and spit out about a teaspoon of gas?

Once again all of you are awesome for helping me out with this.. It'll be running great here soon.. I'm sure it's something simple.

Last edited by dr.ona; 04/09/19 2:09 pm.
Re: New carb cable, new problems.. [Re: dr.ona] #770595 04/09/19 3:05 pm
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"Why would it idle great for a few minutes, and then all the sudden just quickly die and spit out about a teaspoon of gas?"

Sticking carb float might do this, check the float for casting flash or anything else like an overhanging gasket,, perhaps its rubbing and not sealing properly.


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Re: New carb cable, new problems.. [Re: dr.ona] #770627 04/09/19 10:48 pm
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dr.ona Offline OP
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Just an update..
Took the carb off again for final inspection/settings.
Again, everything is spotless inside.
Installed new black tip float needle just because.
The needle itself is on the middle slot with new brass clip.
Top assembly is correct, no weird spring tangle
Air/fuel screw is at 1.5 turns out.
No kinks in new throttle cable.

Bike starts up easy, idles fine, but seems like I need to have it a touch high or it wants to die out.
No slack in throttle cable now.

Went for a ride... pulls great, no sputtering..came to about 5 stops.. died once, started right up.
Get into the driveway, let it idle for a few, barely touch the throttle, like twist it with 2 fingers slowly, bike dies.

Honestly it seems like if I keep the idle turned up high, it would be fine, but who wants to ride around with a high idle.

Do you think having the taller chopper bars vibrating would have something to do with it?
Just thinking way outside the box now, hahaha..

Re: New carb cable, new problems.. [Re: dr.ona] #770635 04/10/19 12:02 am
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desco Online Happy
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What is the idle speed?????


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: New carb cable, new problems.. [Re: dr.ona] #770638 04/10/19 1:18 am
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dr.ona Offline OP
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Around 700-800 RPM...
That seems like the right idle, anything higher and I get a pretty good clunking going into 1st gear from takeoff.
If I try to lower the idle screw it dies immediately which didn't happen before cable change.

With the old cable/handlebars, I would turn the idle screw up a slight bit less than a 1/4 turn and start bike.
I'd let it idle like that until warm up and then turn it down to what seemed to be normal.

Thank you again for the help!

Re: New carb cable, new problems.. [Re: dr.ona] #770645 04/10/19 7:55 am
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Hi DR. That is too slow of idle. It will die at stop lights unexpectedly. Also it makes oil pressure lower than ideal.

The carb has no provision for cold fast idle like a car. Most Triumphs won't idle cold. Takes a good 10-20 minutes many times to warm motor to get reliable idle. You have to hold idle faster with throttle when cold. Warms much faster in summer.

I don't believe your bars are causing this problem unless you don't have any play in cable.

Many of these bikes work better at 900-1050 rpm or even higher in hot weather at stop signs.

How are you setting mixture screw? Sounding like you are a bit lean. After riding at least 10 miles pull over & turn mixture screw in/out slowly & listen for best idle. Smoothest & fastest. If idle gets too fast back down the idle stop screw until it's correct rpm. Then go back to mixture screw & turn in/out until best idle. Keep doing this until you get it good as it can get. Then go 1/16 turn in to bias slightly rich.

Here's the thing. The throttle cable must have some play to allow slide to go lower if you need to lower RPM. Again, turn bars full left/right to verify the cable flexing as you turn doesn't raise idle. After you finally get the mixture & RPM where you want it, one more time check the cable play.

It is important to note how different bike runs & how the idle changes when motor is fully heat soaked. For instance, when I ride freeway for 15 miles at 60-65 mph I come to bottom of off ramp Idle will be 1200-1300 rpm. I turn down the hill to John's house. About 1/2 mile down the hill at stop light idle is now down to 975. I like to keep idle at 1050. A little while later in town the bike warms up again to "normal" & idle is 1050. Going down hill the motor is actually running too cold. So the idle drops. If I set idle at 900 "normal temp" it will want to die at the stop light. I've ridden 3 different Triumphs on this route & all 3 behave exactly the same way. This is very normal & they just do that. I've not found a cure. In town on 100f day, by the 6th red stop light the motor is running hot. It will try to stall. It will often stall at take off. When overheated like this you need to hold throttle at 2000 rpm. Our fuel starts to boil in carb. No amount of heat insulators will cure this. Back with 70s premium leaded fuel this never ever happened. Modern fuel is made for fuel injection, not carburetors

All these adjustments are known as carburetor tuning. It will take some practice to find the mixture & rpm that works best overall. Once you figure it out, & find the best compromise, the carb tends to stay in tune a long time.

With Oregon fuel I expect bike will run better at highway speeds & pulling hills with clip on lowest notch on needle. This will NOT effect lower throttle openings. Will be near 1/4 to 3/4 throttle. Right where E10 91 unleaded likes to run lean. So this clip position often helps. I know tuning guides are very helpful, but when you are on the cusp of lean sometimes you need to just experiment with needle clip & jets to see what is best.

I don't recall your ignition system, but this is where a Boyer or the like can help. The idle timing is much more stable & the advance curve is very progressive up to 3500.

Points ignition tend to allow timing to jump around at idle & just above idle. Advance quickly goes to full advance by 2000 rpm. Stronger springs & making sure auto advance unit is not worn will make a big difference in idle & lower speed operation. But this is another subject. However it's hard to tune carb if timing is jumping around.
Don


1973 Tiger 750
Re: New carb cable, new problems.. [Re: dr.ona] #770646 04/10/19 7:56 am
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Your idle speed is a bit low for a 500 and will likely be very 'lumpy' and likely to stall. They are much happier idling at about 1000-1250; the 650s will idle at that speed but they have bigger flywheels. First gear engagement should not clunk if the clutch does not drag. The idle screw is not meant to be repeatedly turned up and down as that's liable to wear the thread in the carb body and also the o-ring, giving an air leak. Why not adjust the throttle return clamp to make it a bit stiffer and hold the throttle open a little?


Current bike: 1969 Daytona
Previous bikes: '62 Bonnie, '67 Bonnie, '69 Bonnie, '70 BSA Lightning, '71 Bonnie, '73 Honda 500-4
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