Possible Ignition Issues?

1980 xs650special

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Hey all,
It has been a long while since I have posted here, but the long winter months have gotten me thinking again.

I have a 1980 XS650 Special, and I have been chasing very intermittent issues with it over the past few years. Up until this point I have always thought it to be fuel related issues but in dealing with some ignition issues on a different engine it got me wondering if some of these symptoms would carry over to my problems with the XS.
I apologize if I have a lack of detail and I will do my best but I haven't ridden it in a few months things are a little foggy.

First off, the setup is mostly stock with new air filters, carb boots, manual petcock, slide diaphragms, up-sized pilot and main, and other things that I may be forgetting...all this work was done when I was chasing fuel issues.

As for the symptoms, It runs pretty good and I have been happy with performance through most of the range. EXCEPT: it has almost always had a little stumble right off of idle if I snap the throttle fast. And here is where the problems really take an annoying turn. Randomly...and I mean randomly(once was a year and a half between incidents)I can be riding along at any point into a ride, could be 1 mile or 50...and it will start to buck and miss and surge in and out and nothing that I do can prevent the inevitable stall that happens next. If I mess with choke/no choke I can sometimes get it running again...but rough...and as soon as I take it off choke it dies...I end up fighting with it for quite some time until I can either limp it home or leave it and come back later. Then it usually fires up like nothing happened and runs great again.
Also, the last time this happened I noticed as I was limping it home that it seemed like it was running on one cylinder and the other one would cut in and out sometimes.

The PO installed what looks to be one of those green dual output coils from Mikesxs. Could this be a coil on its way out? If so why would it respond to choke after it dies? Also, why would it start and run fine after sitting for a few hours?

Any thoughts would be great, i'm just sitting here thinking about things until the weather gets above 30 degrees again :D
Thanks!
 
Most of your description reminds me of problems people have with gas cap vents. Gas cap vents can clog with hard yellow fuel lacquer and slow down fuel delivery. The way to diagnose this is to open the cap after the bike stalls for a while or open the cap and ride with the cap open to see if there is a quick recovery. I've cleaned caps by turning them upside down and soaking them overnight with WD40 or Seafoam, then blowing with compressed air, repeat. Lots of yellow hard lacquer stuff will be removed while doing this cleaning.

Scott
 
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The stock BS34s do tend to have a bit of an off idle stumble if you still have the stock non adjustable taper jets a thin washer that shims them up a smidge may take care of that stumble. there are also aftermarket needles with a choice of slots for the e-clip. A coil that shorts when hot is one possibility for the the other issue. Often (but not always) a cracked case on the coil is part of that failure mode.
 
Thanks guys,
mrtwowheel- I hadn't thought of the gas cap angle before...when it sits out in hot weather I can hear a whining noise coming from the tank and expanding gases, I always thought that was normal but maybe not?

gggGary- I had heard that these non-adjustable needles could be the culprit but hadn't gotten adventures enough to try the aftermarket models yet...was sort of hoping that the other jet adjustments I made would do the trick.

retiredgentlman- I did replace the original fuse box when I first got the bike and converted over to blade type fuses for ease of use.

The more I think about it, the more I remember how choppy the engine got as it would start to act up. It was as if one or both of the cylinders was simply dying and then immediately picking back up until finally it would bite the dust. Could I tell if there was a coil short from higher than normal resistance readings?

Also, are these dual output coils decent units? What is the advantage to something like this versus two singles? What would you suggest as a good stock replacement?
 
The Green Monster coil is a very strong coil, very high output. It can be a bit fragile. It won't take much abuse, Such as leaving a plug wire unhooked, or leaving the key and kill switch on without the engine running.
All that high voltage has to go somewhere so it can short out the windings or to ground. If damaged like this it may run fine when the coil is cold but can act up as it gets hot.
 
I too have a '80 Special. I call her "the SG". She too would be running along and then stop running. Once or twice a year. I got rid of the glass fuse holder and replaced it with a more modern blade fuse holder. Never again did that happen. I have modded the stock air filter housings (XSJohn mod) and rejetted the carbs accordingly. Made all the difference in ridability. Threw out the dead/dying stock TC ignition and installed a PAMCO W/ elelctronic advance and the Monster coil. Never misses a beat now. Oh yeah, did the "Canadian needle jet" mod. Adjustable needle like the rest of the world got that EPA "forbade" us US riders to have. All in all , not too expensive to do and way better to ride. I did a thread, "Improveing my SG", or something like that a few years back.
 
Thanks guys!
XSLeo: You can feel free to berate me if this is a completely dumb question and a lack of understanding on my part, but I was under the impression that the coils weren't receiving any voltage until the motor was actually turned over? I'm not really clear on how the TC ignition works. But I could see how this would be damaging to the coil in that case. For all I know I may have created this scenario at some point. I have always been careful to ground plug wires if doing any tuning with one disconnected but I was unaware of the key/kill combo being left on. Would you recommend this coil again if I replace even though it can be fragile? Also, is there a resistance reading I could look for to possibly see if there is any internal damage?

azman857: I do hear alot of people talking about the Pamco's but as stated above, my knowledge of how the TCI works is limited and my understanding of the Pamco upgrade is even less. Sounds like you would recommend the Canadian jet mod though? It has been a long while since I have done any carb tuning on it but I believe I remember bumping my main and pilot up one size each. gggGary mentioned that this may take away that slight stumble when I blip the throttle. Was this your experience with the mod?

Money to put into the bike has always been hard to come by for me so I've been slow in improving the old machine...only making changes that have a relatively sure chance of success, so its always helpful to hear what others have done and whats worked for them.
 
You are right a stock TCI box will not "hot soak" the coil, it shuts off when the crank's not turning.
 
Power flows to the coil anytime the key and engine stop switch are on. The TCI grounds the coil to allow the power to flow through the coil. When you first turn the power on, power does flow through the coil for a few seconds. If you don't start the engine in this time the TCI shuts off the power flow through the coil to protect the coil and ignition. When you try to start the engine the TCI senses the engine turning over and turns power flow through the coil back on.
The Pamco has a similar function.
Leo
 
Power flows to the coil anytime the key and engine stop switch are on. The TCI grounds the coil to allow the power to flow through the coil. When you first turn the power on, power does flow through the coil for a few seconds. If you don't start the engine in this time the TCI shuts off the power flow through the coil to protect the coil and ignition. When you try to start the engine the TCI senses the engine turning over and turns power flow through the coil back on.
The Pamco has a similar function.
Leo
Do you know off hand if the Pamco for a 277 engine has this function? I always wondered about that. I am in the habit of starting the bike a quickly as possible after switching the ignition on.
 
XSleo
From petes site.
5. Do not apply power for more than 45 seconds if the engine is not running.

I kinda remember a discussion long ago with Pete that the pamco does (did) NOT have a time out feature.......He felt that simple, low price and common sense was the best answer. We all know how common THAT sense is.
The old Kawi coils were quite delicate, during testing I left the key on a KZ305 for a few minutes, the coil sent up a perfect little mushroom cloud in the garage. looked like an old A-bomb film. Game over for that one. Any old Kaw twin, suspect a bad coil if one side doesn't fire.
 
Do you know off hand if the Pamco for a 277 engine has this function? I always wondered about that. I am in the habit of starting the bike a quickly as possible after switching the ignition on.
The Pamco for a 277 rephase does not have the "cut off the current if engine is not rotating" feature. As I understand the 277 pamco, it still uses the mechanical ATU with fly-weights, etc. To get that highly desirable feature, your bike would have to have the Pamco E-advancer, which is only used with the stock 360 degree engines. I believe Pete programmed the firmware so that the engine had to complete one full 360 degree rotation before power was applied to the ignition coils.

I use the E-advancer and it works amazingly well. With a 277 rephase, as soon as you wave your hand, your Moto gadget is likely to turn on power to one of the ignition coils, so you better immediately start the engine or wave your hand again and turn it off. Maybe you can program (config) the Moto gadget to do that for you???
 
Hey guys, I'm back out in the shed a little bit with the nicer weather. As i've started looking into this again and looking into options for new coils and such, i've found something interesting. I still have to confirm it but I'm almost certain I have resistor caps on the bike right now along with resistor plugs. I haven't checked the caps but they look identical to the NGK resistor caps.

So my questions are, what sort of symptoms or problems would this cause by running a double resistor setup like this?

Also, the coil in question is a green Dyna coil, dual output...I'm looking to replace it but don't have huge funds on hand. Would anyone have any reservations about the "High output replacement 1.6ohm" coil that mikes sells? And if not, what sort of plug/wire setup should I be looking for with this?

Thanks!
 
Resistor caps and resistor plugs will give you a weak ignition/spark for sure. Change the plugs, keep the resistor caps or replace them with new resistor caps.
 
I have twice encountered a very similar random stumbling / a cylinder cutting out unstable idle with my 1978 XS. Made me nearly rip my hairoff.....
I went througt the vent in the fuel tank, carbs, igntion, timing ( mine has points ignition not electronic ) and a lot of other thing. I even ordered a Pamco ignition in case it was the points.

The solution the first time was a loose bolt on the head stay bracket which also doubled up as the ground for the standard ignition. So it would sometimes connect, sometimes not; Random stumbling without any logic.......

The second time it was the coils. They looked fine but when I took them off their mountings and rolled them over, they had a big crack between the bolts so you could see the windings inside!! No way you could see the crack while they were mounted to the frame.
Put a new coil in and problem solved.

These were my solutions for a similar problem you´re having. Hope it helps!

Heimir Bardason.
 
from your description its possible that you have more than one issue going on here.

Taking the off -idle stumble first . You say that this happens pretty much all the time .
For this issue you need to concentrate your attention on the components that most effect your throttle pick up and the throttle response off idle .

Starting with fuel air delivery this is the pilot jet, the slides, diaphrams ,idle air/fuel mix screw adjustment and inlet air leaks. I'm assuming for the moment that there is no ignition timing or electrical issues.

If I drop the clutch and snap the throttle open from idle on my 79 special , the front lifts and the bike is literally catapulted 5-6 yards in less than half a second.! Thats how it should respond when everything is working correctly

As you have replaced your diaphrams recently I would start there first as they have a profound effect on snap throttle response.

Remove the air filters and lift each of the slides in turn ,up to the top with your finger. Shut off the air to the top crescent vent on the venturi mouth with your thumb and let go the slide. Time your slides fall to rest, it should take a minimum of 15 seconds and ideally no longer than 20 seconds. If its outside that time your diaphram is either leaking or your slide is sticking.
Lift and release each slide and check to see that it falls smartly to rest with a descernable click/clunk sound (don't block the vent this time). if it doesn't, either your slide is sticking and needs cleaning or something is causing excessive drag so check the needle , atomiser and slide is not rubbing .

Best to troubleshoot problems systematically, eliminating the most likely candidates so that you can eventually arrive at the solution rather than random component replacement in the hopes that it cures the problem
 
Thanks peanut! I have done the slide test and it checks out free and clear. Update on the bike: I put on a new coil and non-resistor plugs and kept the resistor caps. The bike is nice and snappy now with no hesitation and pulls real smooth. I haven't gotten a chance to take it for a longer ride to see if it acts up randomly as it has in the past.

I do still have the slight pop on my left hand cylinder when idling and a bit louder pop on deceleration from the same cylinder. A little bit of richening of the mixture screw had a small effect on it at idle but not much. I found an air leak around my right hand throttle shaft seal but nothing on the left. Also, I did notice when I pulled the old plugs that the left side looked a bit leaner than the right but after a short ride the new ones look identical. How long should I need to ride before I can get a good read on the plugs?

At this point I have some other projects and i'm just in the tinkering stage with this one, happy to be able to get it out and around the block every now and then. Does the popping pose any long term threat to the engine? It is rejetted to be running richer so I don't think I run too much of a risk of being excessively lean, but what do you guys think?

Thanks much!
 
Also, I have a '74 KZ400 that I am starting to strip down, does anyone know of any good online resources for these little bikes?
 
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