Starts running rough stalling after warmed up

pristic

pristic

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Guys,

I know and have read the threads related to this however am stuck.
Before I went to the PAMCO I could ride over an hour and it would be fine (I have always had plugs fouling in the past though - to me means running rich) but keep reading.

I installed the PAMCO and things are great, pull the choke, start her up, almost first kick every time. Runs sweet... happy days. However, I took her about 5kms from home, she ran fine, as I got into the underground carpark, she started idling low and wanting to die, a bit of throttle and she was ok... but as soon as I back off the throttle she just stops, no backfire, no pop, just like I turn the key off.
I kick her immediately and she fires right up again... like nothing happened.
I rode home, same thing.

To me its either the coil or the floats.
The coil if its playing up when warm... but somehow dont think thats the prob.
The floats (if too much fuel is getting in, then when cold its fine, likes the fuel) when warm is fouling/flooding. Ill pull the plugs tonight to check.
What else could it be? Could timing cause this problem?
With my timing, its quite retarded on idle... and I cant get it to be advanced to the correct mark on idle... if I turn up the idle, it is better... but doesnt solve my original issue of it stalling.
Its not the vent cap either, I tried to open it to see if that makes and difference but it doesnt.

Any other ideas? I cant get her over to Geoffs for a tune for some time, and I dont ride her often at all...

To add, its a brand new ultimate coil, new wires, new caps, etc. The plugs are BP6ES and NOT iridiums (shouldnt make a difference?)

Im confused as it happened after I put in the PAMCO and e-advancer... with points it was a pig but didnt have this problem. This is the ONLY issue I am having, no other issues... basically, I dont feel confident taking her on a longer ride as I know the first set of lights or traffic I hit will then be a pain... when she is playing up on idle, if I then take off again and sit at speed, its fine, you dont notice anything at all. its ONLY at the lights/traffic etc.

Make any sense?

Cheers,
Peter
 
Hey, Peter, if it occurred on one cylinder, I would suspect a bit of grit got into either a pilot jet, or a pilot air bleed. On both cylinders, I would lean more toward ignition...
 
The pilot controls the idling. In an ideal world if it idles fine that should be it, but it cuts when you have brought the main jets into play (opened the throttle).

There are a number of things it could be, but the carbs are the first port of call.

Anlaf
 
hmmm, ok cant help with the carb info... its how I got it... I cleaned it a long time ago though... open pipes with good 4" baffles. No filters at all at this stage (and yes, was still fouling plugs prior to PAMCO - so ill update tonight)

Twomany - unsure if its on both... when it dies, it just turns off.. only reason I know its playin up is because I expect it. If you or anyone else rode the bike you would do this.
Wooohoo, this is great... 20min later... woohoo, this is great, stop at lights. "Hey, why did it turn off" then kick it over and ride off...

I was thinking pilots also... or floats?
So a tune is in order regardless.. both electric and fuel .

Yes, I have an inline fuel filter. I actually thought MAYBE the fuel was the prob, but beats me...
 
I've had this on occasion, when an errant speck found its way to a pilot jet, or a bleed air orifice. Sometimes, the speck would dislodge from the pilot, and idle fine, until couple minutes later. Same symptoms when bleed air sucked-in a speck, only would remain fouled. Carb cleaner pressure thru the idle mix screw opening, forcing the speck to blow out, would often give temporary relief, but more importantly, would confirm the diagnosis...
 
How can I check the pilot circuit flow without taking off the carbs? Is there any way?

But, I get the ideas about a fuel blockage in the pilot... but why would it happen ONLY after a ride/warmed up... If I kick over the bike tonight, hasn't been run in a week... it will start and idle no problem. If I go up the road and back down, then let it idle it will still idle fine.
Only when I have run her on say a 10-15min ride then come to traffic or lights does she turn off.
Also, I don't let her sit idling long... not sure, maybe from the old '76 mini days but I never let my cars or bikes idle long...

Ill pull the plugs in about 10mins and see how they look and upload a pic too... I know if the pilot is blocked it will mess up the idling and stall and stuff but this seems like its EVERY time I ride, only AFTER a ride for a while then at lights.

I have no problem ripping off the carbs and cleaning if I have to, but me thinks its not a blocked pilot system as it idles fine... EXCEPT after a ride and then coming to a stop. Know what I mean? If I misunderstand how the pilot circuit works or something then I am happy to be educated.


Any other ideas apart from the pilot circuit?

So far we have the following possible:
1. Pilot circuit dirty - clean it and try again
2. Electrical . Where? What should I look at?
3. Timing - Again, at a loss here as its timed as good as I can get it. Might need more input from PAMCOPETE here.
4. Bad coil - doubt it as its an ultimate and brand new.
5. Plugs - but I would expect it would stumble and break up under load with spark problems, not go well and only fail on idle. Right?

The fact that it kicks nice, runs nice, pulls hard, etc all make me think it IS something to do with the idle circuit... but I cant say.

Can anyone answer the following questions definitively?
1. If the timing on idle is too retarded - what effect does it have? Will the bike stall yet let the bike ride nicely?
2. If float heights are wrong, allowing too much fuel to go in, would that cause stalling yet let the bike ride nicely?
3. Would a blocked pilot be a problem on idle all the time? or under particular conditions?

Be back in 15min

Thanks for all the help so far!


Cheers,
Peter
 
My opinion...............its not carb problems, more likely ignition coil or electrical connections/switches.

Even though the coil is new, it could be defective when it heats up. Do you have it mounted so that the iron core is contacting the metal bike frame so that you have a heat sink. Some coils heat up and need a heat sink, and some coils do not heat up. Pamcopete recommends a heat sink for some coils.

Items such as fuses/fuseholders, ignition switch, kill switch, can develop high resistance and cause intermittant problems. You could run a by-pass wire around these items to see if the problem goes away.
 
You don't mention what year it is. On the years that had the four fuse block on top of the battery can cause many problems. The clips that hold the fuses get dirty, this leads to a higher resistance, higher resistance causes extra heat, extra heat weakens the clips. The weak clips grip the fuse less causing higher resistance. A repeating cycle that leads to broken clips.
This weak connection can get worse as thing heat up. Then cool off enough to work.
Leo
 
Pristic, about checking the pilot flow without taking off the carbs - 5twins is the demi-god of carbs, but if you are idling well to start then the pilot is functioning. Checking for foreign bodies in the carb requires carb removal.

Anlaf
 
Both Retiredgentleman and XSLeo suggest it might be an electrical malfunction, and to my mind checking out the connections is the next step - have just replaced the negative cable on my battery when I found under all that tape it was, in fact, a spark plug cable (HT lead). Previous owners, eh? who'd have 'em?

Anlaf
 
These bikes can be quite timing sensitive at idle, just 2-4° extra retard can cause idle to drop enuff to stall. Sounds like an opportunity to build a dashboard timing indicator....
 
Saw a gadget like this for the custom car market. Like a digital voltmeter, imagine another display that reports ignition timing, with a knob that lets you adjust it...
 
Sorry for delay, my daughter decided to get a bit difficult last night so bike playing time ended fast.

1981 model however VERY simple wiring (all rewired)

Bike is completely re-wired and has new cables. The reg/rec are original though.
Earths all check out good, and fuses (only have 2) are great.

The timing could be part of it however not sure. I simply cant get it to time in on idle (ie/ if you look at it, the timing mark is about 1cm to the RIGHT of the F mark on idle. If you give it some throttle its ok... so its retarded on idle...

If its NOT the pilot circuit (which I dont think it is) then could it be float height?
Wondering because on idle when cold more fuel would let it idle nice, but when warm it would be running too rich right?

With electrical, I need to think more. Since the scenario is that it only started doing this AFTER PAMCO/e-advancer I am wondering what part of the circuit could be under stress. What I mean is, the ultimate coil is much stronger, and could be stressing part of the circuit as it all heats up.
YES, the coil is mounted with metal coil stands directly to the frame. Coil doesnt feel like its overheating (it gets warm but not hot hot)

If I was to bypass anything, im not sure what to bypass as its such a simple wiring setup. The only things I could bypass would be the key (on off) and fuses...

My thoughts at this stage are to get the tune right first... get the timing set right (even though I am really stuck there) but do the cam chain adjustment, etc first.

Happy to try and test etc but need to know where to look. Its just a very odd problem.

Another thing to note:
1. The petcock goes down out of tank and fuel line sits on the top of the head touching the motor a bit. Could fuel be "boiling" or anything? It seems to flow fine and into the filter... doesn't matter? dunno - just throwing it out there

If I could narrow down fuel vs electrical that would be best, but they often disguise themselves!
 
Hmmmmm, with a retarded idle timing, the carbs have to be opened up a bit to hold idle speed, likely running more on transfer ports than idle port. With a larger carb opening, but still at idle rpm, the manifold pressure is higher, less air flowing thru carbs to pull fuel.

There's the seed, let's see if it grows....
 
Twomany I prefer the buds. You keep your seeds hahaha
Ok. So I'm guessing you mean timing and pilot.

This is interesting though. Sooty and black.
Fark me!

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Posted via Mobile
 
Yes, those plugs are very black, and they're 6's too which are hotter and should burn even lighter than the stock 7's. You either have an overly rich condition related to the carbs or a weak spark. I would test the spark (ground a plug to the head) and observe the type and amount you're producing. You want a nice fat white or blue spark, not a wimpy little yellow one.

If the coil was acting up once hot, I don't think the bike would restart immediately. You'd need to let it cool for a while, like maybe 15 minutes to an hour. However, maybe the spark is turning weak when it's hot. I would test the spark cold and then test it immediately after the bike stalls again to see if spark strength has diminished.

In the carb department, yes, check the float height. Your BS34s are very sensitive to that setting. While in there, you'll also want to check the jetting that's installed (and write it down for future reference). It's possible the carbs are just jetted too rich. The plugs are getting to the point where they're so black, they're nearly fouled. Higher speed running will spark through that but at idle it stalls. Having the timing so retarded isn't helping matters either. The idle is rougher and slower like that.
 

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