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Bike stalling at developing and idle sometimes?

14K views 98 replies 8 participants last post by  misfitJason 
#1 ·
Help me figure out my problem here because I can’t figure it out.

Bike is a custom built softail that I built. I built it with an oem 80 inch evo and up until about a month or two ago it had no problems. I recently bought a brand new s&s v111 and swapped it into the bike. Carb is a super e (same one that I ran on the 80 inch) with a 32 intermediate and 78 main. No adjustable air bleed. I have about three hundred miles on the motor as I type.

The ignition is a dyna S set appropriately for this motor.

I have confirmed I do not have an intake leak and am using all of the appropriate hardware for this carb and motor.

The motor runs excellently except it stalls every so often on decel and sometimes will stall at idle. At any type of acceleration it has no issues and runs strong. When it stalls it coughs. The idle air mixture (whether rich or lean) doesn’t make a difference on the stalling. After it stalls I can start her right back up.

None of these problems existed before he motor swap with all the same parts. I have since rebuilt the carb and changed the coil with no difference. My next thoughts are my mechanical advance (although it turns free and easily) or possibly there is crap in my tanks causing a issue with gas feed. Again I am running the same parts that I was with no problems before.

The spark plugs look good as far as the mixture goes. I even replaced the plug wires. No difference.

Any suggestions that you guys have I would appreciate. Thanks in advance.
 
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#2 ·
Check your advance weights.
my shovel used to do that at some point in it's life... although the advance weights worked fine and were free, on close examination, the slot where the weights slide into had been chewed up .

Replaced it and sorted it out.

I'll try find a photo of what I mean, I must have it somewhere as I take photos of everything.
 
#3 ·
I know you know what you're doing, but your idle speed is nice and high, right? Just checking.

How about your fuel line routing? Sometimes too big a "loop" causes exactly what you're talkin' about.

And what about tank cap venting? Have you verified that with a blow test?
 
#4 ·
It wouldnt accelerate if it was a starvation issue, especially under load.

Put a dvom or led test light in line with the ignition’s voltage. Lets see whats happening as it slows and idles. Im assuming it acts like you shut off the key. Can you rev it out of the stall or does it continue until dead and then easily restart? My suspicion is you can on decel only and not always. Maybe if it was coming down from a higher rev can you catch it...

Fuses or Circuit breakers.... what have you?
 
#6 ·
It wouldnt accelerate if it was a starvation issue, especially under load.

Put a dvom or led test light in line with the ignition's voltage. Lets see whats happening as it slows and idles. Im assuming it acts like you shut off the key. Can you rev it out of the stall or does it continue until dead and then easily restart? My suspicion is you can on decel only and not always. Maybe if it was coming down from a higher rev can you catch it...

Fuses or Circuit breakers.... what have you?
If I am coming to an idle I can sometimes throttle it out of the stall. Sometimes it will just dies out at idle whether on decel or just sitting there. I can however hold the idle faster to sometimes avoid it. I am running circuit breakers.

My idle is set currently to about 1100
 
#5 ·
I tore into a couple of things.
















The fuel line was new when I changed the motor and this is how it's routed. The mechanical advance looks good and moves free.

The cam seal is leaking a little. Will eventually have to change that out. All of the wires coming from the ignition module are intact and good.

That little black boot on the plunger looks like this when I took the picture. I can't remember from memory if it's supposed to be all the way up or not. That could be a possibility.

The butterfly on the carb is nice and tight and not loose.

I don't have time to check the petcock screen or tanks. There could be some crap in there. I would also like to run a compression test on the motor when I take the tanks off to check them for debris. But I'll have to unplug the acrs. Can anybody think of anything else or see anything that jumps out at you?
 
#9 ·
We're getting far afield of this problem, but put a loop in your fuel line that's too long for the manifold vacuum to deal with. Your bike will occasionally simply turn the fuck off when the line inevitably vapor locks. You will be running out of fuel - starving - but it will run like a peach if jetted correctly. I have repaired this problem on multiple bikes. Rich or lean does not seem to matter per Jason, so I've not yet ruled out a fuel supply problem as you have.

Back to the problem at hand... with respect to an intake leak, when you tested it, I am assuming you A) do have a VOES port on the manifold and B) it was tested and verified as sealing? I've used vinyl caps on them which get "greasy" and leak when hot.
 
#10 ·
I am not running a voes and have the ports (2 of them) capped off with polyurethane caps and then zip tied so they won’t come off. I checked the intake seals with a propane tank with negative results.
Everyone keeps telling me to check the bolts on the two sides of the carb that hold the throttle shaft on because they can wear.

The little rubber boot that covers the accelerator pushrod has seen better days. I can shorten up the fuel line and see if that helps. So far I know this

When I set the timing per s&s specs (advance mark leaving the left side of the window) it takes the enrichment to cold start it. I do get starter stall. But it runs well. But it stalls on decel and sometimes at idle randomly

If I advance the timing at the plate a degree or two, it will not require the enrichment to cold start it and the starter stall is less. It runs good here too but the revs hand up when moving, letting off the throttle, and coming to idle. It did not stall though.

Both times idle air screw was adjusted for the timing settings and idle is about a thousand to 1100. I now have 350 miles on the motor. I don’t see any evidence of oil burning on the plugs. On a side note I do notice a little oil mist collecting at the bottom of the teardrop air cleaner.
 
#11 ·
I checked the intake seals with a propane tank with negative results.
Definitely check the throttle shaft, but pressure testing is the only way to be sure... 13-15 psi is more than enough.

I'm not certain this is the issue, but it would be nice to rule that out.
 
#14 ·
s&s v111 and swapped it into the bike. Carb is a super e (same one that I ran on the 80 inch) with a 32 intermediate and 78 main.

Any suggestions that you guys have I would appreciate. Thanks in advance.
A 111" at sea level with a Super E and .032 intermediate jet? I'd be willing to bet a bigger intermediate jet will cure that. Definitely a .033, and even a .036 if the 33 doesn't make a difference.

I've got an 88" shovel that had same symptom. I chased absolutely EVERYTHING else b/c the plugs looked good, and the bike didn't exhibit other symptoms of being too lean, etc. I ran out of other things to do, so I finally went from a .031 to a .032, and that the symptom finally went away. And even then I went up to a .033, and the motor was even happier when coming down off idle.
 
#16 ·
I have a 33 at home I think. I will give it a shot. I am leaving for a nice vacation coming up and will dick with it more when I get back.

My gameplan for now is.... I am going to order a new rubber seal for the accelerator pump rod and when I have it disassembled I am going to check on that throttle shaft for starters. Shorten up the fuel line, run a compression check, and check the fuel tank for debris. CHeck the petcock screen.
 
#18 · (Edited)
With the advanced timing (by about two degrees) it has not stalled on me at all. However, it is breaking up just off of idle or at low rpms. Like it’s missing. The acceleration is not as strong as the recommended timing. But it is waaaaaaay easier to start!

So with a bit more timing she doesn’t stall but is not as smooth off of idle. Any new suggestions with this new found info. Still think larger intermediate jet? I just realized that I never told you guys what exhaust I was running. It’s a kerker supermeg 2-1. And the idle air adjuster screw is at 1 1/2 turns out.
 
#20 ·
I also ordered up a replacement s&s rubber fuel line. I am going to in a specified order replace some parts in this order so I can see if one of these fixes it:

Scope the cylinders and run a compression check once one of the tanks halves are off. Then go from there.

Check petcock screen and debris in tanks

Replace the bellows seal and fuel line

Replace intermediate jet with a little bit richer.

Change out gas tank cap with vent

Change out mechanical advance

Replace ignition as necessary
 
#21 ·
Back from vacation and started playing with a couple of the parts I ordered that had arrived.

I put some new vacuum plugs on the manifold. I also borrowed a new mechanical advance to see if that makes a difference. I won't be able to ride it until tomorrow morning. I did put the timing back to where it was so I can see if I still have a problem.

I pulled the mixture screw. I didn't notice a o ring anywhere for that. But it didn't appear buggered up.

If these don't make a difference My next step is a replacement fuel line and check the petcock screen and possible debris in tanks. Enjoy the pics.


 
#29 ·
Update:

None of the replacement parts seemed to make a difference. So I started playing with jets.

I installed a .33 intermediate and that cured all my off idle hesitation and hinting that the bike was doing. I literally just got back from a ride for about five miles and she did not stall out on me but it wasn’t really far enough to tell as of yet. I am going to ride her in the morning and see. It might even be worth trying out a 34 intermediate. I did drop my main down to a 76 and now she seems to pull better top end.

If she continues to stall I am going to try and take video of her doing it to aide in the process
 
#44 ·
Update:

None of the replacement parts seemed to make a difference. So I started playing with jets.

I installed a .33 intermediate and that cured all my off idle hesitation and hinting that the bike was doing. I literally just got back from a ride for about five miles and she did not stall out on me but it wasn't really far enough to tell as of yet. I am going to ride her in the morning and see. It might even be worth trying out a 34 intermediate. I did drop my main down to a 76 and now she seems to pull better top end.
I already said it once, but try a .036 jet (it's the next size up). You have a big motor, a Super E, and you are at sea level. Plus you said that you went from a .032 to a .033 and it sounds like things got better. It's the simplest and cheapest thing to try before jumping through all these other hoops. But I also say this because I wrestled with the exact same symptom on an 88" with a .032 jet.
 
#33 ·
I have never done that and don’t know how to. Could you please explain it to me

I did test it warm with propane and wd40. The idle didn’t change when checked at the throttle shaft ends or at the seals. But I was doing it quick and I am going to recheck it again.
 
#35 ·
I have never done that and don't know how to. Could you please explain it to me

I did test it warm with propane and wd40. The idle didn't change when checked at the throttle shaft ends or at the seals. But I was doing it quick and I am going to recheck it again.
I showed it on another thread but here you go

Buy a tractor tyre air valve and on get a thick a piece of steel, then drill some holes to bolt to manifold and one center one for the tyre valve.
I seen some that are done with air compressor fittings, but if you dont have an air compressor you can use a foot pump. and if you have an air compressor you can you the tyre fitting and gauge.

one of these.



then you make one of these:



and put some air in it.



Now.. on the "air through it".
You have to remove your pushrod covers and look at the intake valves and make sure both pushrods are at the bottom - meaning intake valves closed.
You pressure some air into it - doesnt need much - and it should be able to hold air there, something like 1.5bar.... if it escapes you'll probably be able to hear it, start spraing soapy water around the manifolds and check where the bubbles are.

hope it helps!
 
#34 ·
Ah. I have a little business venture going in this arena, so manifold leaks are of great interest to me. I believe they affect a ton of old bikes — Knuckle, Pan, and Flathead are the worst offenders, but Shovels suffer some, too. Evos and newer are much better, but you sure sound like you have an intake leak. I think a lot of people are tuning around leaks.

Effectively, what you want to do is remove your carby, and either make a flat plate with an air line fitting in it or a rubber plug with the same, and then shoot air in there at 10-15psi. Use leak detection fluid or soapy water out of a spray bottle, and wait for the bubbles. The right amount of bubbles is no bubbles.

This may or may not be your problem, but it would definitely rule out an intake leak.
 
#37 ·
Ah. I have a little business venture going in this arena, so manifold leaks are of great interest to me. I believe they affect a ton of old bikes - Knuckle, Pan, and Flathead are the worst offenders, but Shovels suffer some, too. Evos and newer are much better, but you sure sound like you have an intake leak. I think a lot of people are tuning around leaks.

Effectively, what you want to do is remove your carby, and either make a flat plate with an air line fitting in it or a rubber plug with the same, and then shoot air in there at 10-15psi. Use leak detection fluid or soapy water out of a spray bottle, and wait for the bubbles. The right amount of bubbles is no bubbles.

This may or may not be your problem, but it would definitely rule out an intake leak.
[JP said:
;2061482]
I have never done that and don't know how to. Could you please explain it to me

I did test it warm with propane and wd40. The idle didn't change when checked at the throttle shaft ends or at the seals. But I was doing it quick and I am going to recheck it again.
I showed it on another thread but here you go

Buy a tractor tyre air valve and on get a thick a piece of steel, then drill some holes to bolt to manifold and one center one for the tyre valve.
I seen some that are done with air compressor fittings, but if you dont have an air compressor you can use a foot pump. and if you have an air compressor you can you the tyre fitting and gauge.

one of these.



then you make one of these:



and put some air in it.



Now.. on the "air through it".
You have to remove your pushrod covers and look at the intake valves and make sure both pushrods are at the bottom - meaning intake valves closed.
You pressure some air into it - doesnt need much - and it should be able to hold air there, something like 1.5bar.... if it escapes you'll probably be able to hear it, start spraing soapy water around the manifolds and check where the bubbles are.

hope it helps!
Thank you
 
#38 ·
I was just thinking about this. Being things are somewhat electronic in the ignition area,..... does anybody think that a leaking cam seal letting a little oil past, could be my issue?

The cam seal leaks a little bit leading oil into the ignition area. Could it be covering up the pickups?
 
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