Sudden loss of power then fuse blows? Help please

1976 kz 900 with dyna. After 50 mile ride then 10 minute stop, yesterday...when restarted, rode 1/2 mile and bike suddenly lost power. felt like it was running on only 2 pots. 1/2 mile later, 10A dyna relay fuse blew. replaced 10A fuse with 20A to enable limp home KNOWING something was likely to cook but better that than be stranded 50 miles from home at 7pm on a sunday, 20 miles west of Columbia Tn.

Just now put timing light on 1 and 4 and both firing but neither 2 or 3 firing. popped off the Dyna cover and looks like i cooked the 2/3 Dyna pick-up. Every time I replace fuse with 10A and turn on the ignition, to start the bike, 10A fuse blows immediately.

Took off 2/3 coil which is showing no ohm reading between secondary outputs SO, changed out 2/3 coil for what I thought to be a "good" coil and changed out Dyna for another I had in the shed. "good" coil showing what I believe to be good readings but same problem. 10A Fuse blows every time.

Disconected both primary wires from "good" 2/3 coil and fuse does not then blow when ingition turned on. Replaced "good" 2/3 coil with an Exell "super coil", primarys both connected and fuse does NOT blow BUT, now getting NO spark from either 1/4 or 2/3!!!!!!!!

Are there any tests for the Dyna to make sure that's good? Any thoughts please, thanks.

BH

check to see if your frame is live it sounds to me like you may have burnt or pinched a wire off or melted them on the exhaust system the only thing that can cause the kind of event is a major short to ground.

Thanks for the advice. I'll check this evening. Took the thing apart last night and discovered it appears I've lost the 2/3 coil and, in the process of attempting to get home, using a 20A fuse in the Dyna power relay lead, I've cooked the 2/3 Dyna pick-up. My feeling is that the coil shorted out internally which then, (when I plugged in the 20A fuse, caused the Dyna 2/3 pick-up to melt/blow chunks? Is this likely?

Called Dyna last night and have sent them the ignition and coil to test/replace.

Those Dyna people are EXTREMELY helpful. The ign is 5 years old and the coil is who knows how old. We'll see what they come up with.

Have discovered a somewhat melted white connector in the headlight bucket. Will probably solder & shrinkwrap all the wires in that connector so as to do away with the plug/connector.

BH

Spoke with Dyna this afternoon and the coil was shorted out on the primary side. We think the dyna pick-up was getting a full whack, in effect, without the coil in the circuit (no resistance), due to the short, thereby cooking the Dyna pick-up.

BH

Nice to see you around Barney, been busy? Been awhile...glad you're back

Thank you OKC. Too much stuff going on in life I'm afraid. Family, work, STUFF. I'll try to be more regular.

BH

Two new green coils and new Dyna S just delivered from Dyna. Will fit all tonight when I get home from the office and report back (after the ride).

BH

BARNEYHYPHEN wrote:

Spoke with Dyna this afternoon and the coil was shorted out on the primary side. We think the dyna pick-up was getting a full whack, in effect, without the coil in the circuit (no resistance), due to the short, thereby cooking the Dyna pick-up.

BH

Sounds right. That Dyna circuitry is probably a transistor or SCR to ground that carries the full coil current when it turns on. A shorted coild would take it out if it has no fault detection circuitry to disable the drivers that turn on the internal switch. Odd that they wouldn't put that in considering what a common failure mode a bad coil is.

Got the new coils and Dyna S all hooked up last night. Took the bike out for a short 20 mile circuit and seems to be running very strong. Seems to be a lot perkier with the new coils? had to lengthen the three mounting slots about 3/16" but no big deal.

Haven't fine tuned the timing yet but will get that done this evening. Thanks everyones thoughts and input on this.

Just one question...The advance mechanism seems to get the timing fully to the "F" mark around 2,000 RPM. The two springs appear to be tight and not stretched. Can the advance mechanism springs lose their "pull" over time, even though they don't appear to be stretched? Where can we obtain correct new springs?

Thanks.

BH

Try Z1 enterprises. Jeff Saunders seems to get stuff nobody else can.

Thanks, I'll drop Jeff a line today.

BH

I've searched a lot for those springs on a 550, but couldn't find them anywhere. Kawasaki only has them as part of the advancer mechanism. $$$

What I've done is squeeze one loop on each spring a tiny bit. That usually gets it back to the original spec. for when the advance should be all-in. Be careful, though, it's easy to over-do it. It only takes a tiny bit of a squeeze to make the end loop a little smaller.