1980 GS550 condenser problem

[reabo]

Hi guys. This has been doing my head in for a couple of weeks now. The bike started misfiring,check ignition timing statically and set perfect. Check with a strobe and timing is all over the place on 2/3 but perfect on 1/4. Check statically again and perfect but pops and bangs riding it.After banging my head against the wall a couple of times I figured out it is the condenser for 2/3 coil gone. New condenser, Kokusan Densi ignition so both condensers replaced, timing checked and perfect with strobe. Go for a ride and everything is good for twenty miles then starts slight misfiring again. Back home, on the ramp and condenser for 1/4 gone. (If I connect a working condenser to points 1/4 all is good again).
here is what I have done to the bike

New points
New condenser (I have another spare)
Rewired coils to points.
New coils, 4 ohm coz that is what was on there.

I know I can fit a dyna and loose the problem but I machined the timing cover out and fitted a perspective window so I could see the points and when she is running right she is an absolute joy to ride.

Anyone got any ideas?
The Dyna is a realistic option and as much as I want to keep the points it is where I am looking but I really do want to keep the heritage and interest of the points but not to the point where I can't ride the same thing. Any help would be appreciated.

[tobaccorancher]

Have you tested your condensers? They are just big capacitors, and are unlikely to fail as frequently as you are describing, especially since they only see 12 VDC. Your description sounds more like something is loose mechanically and your "half-circles" that the breaker points are mounted to are moving

[reabo]

Thanks tobaccorancher, testing condensors is by replacement for us normal people. I have heard a basic check can be done with a multimeter but I have swapped the condensors over to the opposite coil and the misfire follows the condenser so I am pretty sure it is the condensor.
I followed your reasoning earlier and all screws on the mounting plates have spring washers and are deffo tight.
And absolutely they should not fail that quick, that's why it is doing my head in
Hopefully it is something silly I have missed so all suggestions are welcome.

[Gorminrider]

All just a guess on my part. It's been awhile since I've had points and never dealt with your issue. But I won't let that stop me.

sooo, what blows a Condenser? They are rated for Voltage and capacity (farads) but voltage is the key- too high a voltage can pierce the insulation separating plates...so, possibly, the voltage that side (1 and 4) is too high...I would look into that.
You'll firstly have the obvious possibilities of A) a crummy condensor out of the box and B) the wrong replacement
from there you'll need to goto wiring and coils...if the condensors are ok per the obvious, then they are getting the overload from the thing that can produce high voltages and that'd be the coil....You are using replacements? Be sure they are wired correctly and failing that, consider swapping in another coil.

[Grimly]

Have you tested your condensers? They are just big capacitors, and are unlikely to fail as frequently as you are describing, especially since they only see 12 VDC. Your description sounds more like something is loose mechanically and your "half-circles" that the breaker points are mounted to are moving

They see a lot more than 12V.

[reabo]

Thanks guys.
The problem isn't just on one side. I have had the condenser go on 2/3 first. Then after fitting a new condenser it went on 1/4. Then again on 1/4. I replaced the coil but it made no difference. The same thing still went. I can connect a known good condenser to earth and the points and there is an instant fix on the spark, tested with a timing strobe and a plug cap which lights up when the plug sparks. The only constant is I can do about 20 miles and it gives up. It makes no difference if I take it easy or if I thrash the life out of it, twenty miles and that's it.
looking at the advance the little round symbol has what looks like " h9 " inside the circle. Could it have parts from both ignition systems? Would it be able to run if it did?

[Gorminrider]

The points ignition is so simple I think it's worth it to find the problem... You have the shop manual? You likely know the condensors are "supposed to be" .0.17->0.25 uf..I think close counts it's mostly about the size that fits in there really...and timing -not much to go wrong and it's pretty obvious when it does-I don't know how that would kill capacitors either.

One idea that might cause this is the charging system...if the battery is not connected, or the regulator is not holding the voltages down, the bike will be running at a high pulsing voltage. Worse, if the charge isn't being rectified, you will have AC running through the bike. Lights won't care but the coil and condensers will-they are probably the only thing that would be excepting really high voltages. A pulsing headlight would be a clue but a test with the voltmeter when running would be an easy way to cross this off a list...also, just running the bike with battery alone for a guaranteed steady DC

I'm thinking too that your symptoms suggest something is getting hot and breaking down . Once a component is burned the first time, the symptoms will repeat ....
550 ignition.jpg

[tobaccorancher]

Grimly is correct about the condenser voltage as the points open. When this happens and the field collapses in the primary coil the voltage spike is dissipated across the capacitor. So, the capacitor will see high voltage spikes when the points open, but this is a 12VDC system, and the points are designed to handle this. Are you sure that your previous sets of points really failed? How many failed? I really think that your problem is more mechanical in nature. I re-read your description above, and am wondering if your cam chain might be loose. Have you tried re-installing (or checking) one of your "bad" condensers to see if it really is bad? That would nail down for sure whether this issue is electrical or mechanical

[reabo]

No points have failed. It is the condensers that are failing. This conclusion is reached by the fact that the ignition timing is all set correctly. Go for a ride and it starts to misfire after about 20 miles. The timing when checked with a strobe is all over the place and the points are sparking. Whilst the bike is running a known working condenser is connected between the sparking/ misfiring points and everything goes back to normal timing and sparking wise. Disconnect the new condensor and the strobe is all over the place again.
The timing chain is nothing to do with the the ignition timing, two totally separate systems. If the problem was mechanical the only mechanical part of the ignition is the advance unit. This works as it should. When the timing is all over the place it is retarded as well as advanced just totally random.
If the bike was running AC without being rectified to DC problems would show up elsewhere, and the sparks from both coils would be all over the place surely? Also my battery would be fried from the AC current but it is maintaining a healthy 12.7 volts.
I think you can see why it is doing my head in. It is such a simple system but I cannot see what is going wrong.

[tobaccorancher]

How many condensers have failed so far? Also, maybe you have a bad ground.

[reabo]

4 have gone altogether. They are mounted two together on a single mounting plate (khoukosan ignition )but only one condenser goes. the other is ok. Earth is good, have checked it with a multimeter

[Gorminrider]

...I think you can see why it is doing my head in. It is such a simple system but I cannot see what is going wrong

I absolutely can.. : (
Looking over your shoulder as we are, offering ideas- well that's mostly in the hope it triggers the solution you will find.

[Gorminrider]

And I would be very annoyed if someone asked, "condensors backward?" (sorry-no stone left unturned) ( I don't think they have polarity except what's put into them but it might be a clue if you find them different on testing them)

here's a link where someone is taking them apart and he's not impressed by quality. Maybe you've a bad batch?

https://www.nonlintec.com/sprite/cap_failure/

[tobaccorancher]

From post #9: "Whilst the bike is running a known working condenser is connected between the sparking/ misfiring points and everything goes back to normal timing and sparking wise. Disconnect the new condensor and the strobe is all over the place again."

Are you using test leads to connect this condenser while the bike is running? If so, can you tell us exactly where you are connecting these leads? Also, if I am reading this correctly, do you see arcing on that condenser's contact points before you connect the additional condenser?

[tobaccorancher]

Also, for the four condensers that you think have failed: have you tried re-using any of them? Can you tell how they have failed? Open circuit? Short circuit?