Anyone have this happen?

Been searching thru the forums and looked thru shop manual, even chatted with my local bike shops about it and they scratch their head.

Curious with all the experience and knowledge that dwells on this site if anyone can throw me some ideas of what might be.

My bike ( 79 KZ1000st )with 22,000miles on it has been losing power intermittently.

You will be riding along and suddenly it feels like 2 or 3 cylinders shut off and bike barely can do 30-40 mph and won't idle. Then whether you pull over or stop or try and keep riding it fires back up in anywhere from 10 seconds to several minutes of this near engine stall out.
It feel like electrical problem but could it be carbs? It can't be heat as I am in Canada and am riding in really cool temps 50 to 70f these days.

Here is some history on bike to maybe help me figure this one out.

Bike has been redone quite a bit this year.
Had carb completely taken apart and cleaned/ synchronized in spring and about 2000 miles ago.
Had cylinder bored to 1075c and put in big bore wiseco pistons etc.
New valve seals and valve seats re-cut ( 3 angle cut)
has new K&N filter, new plugs, and oil changed often.
My original coils had lots of big cracks so replaced with Dyna DC1 3 ohm coils (green ones).
Put on a Vance/Hines Megaphone 4/1 exhaust.

This weird stalling out/sudden power loss issues didn't start right away after any of the work but just did over the last month. Bike runs incredible when this isn't happening. It is a rocket that runs like a dream and sounds like one too, then just randomly now and then it will do this. It feels like someone pulled a couple plug wires off while you were driving then after a minute or so they stick them back on.

My guess at first was loose wires? all new plug wires are perfect and tight. My coils were good too but i wondered if too close to engine so i drilled new holes in brackets and moved them up all I could away from valve covers, didn't solve problem. Bike does not have points and has electronic ignition, could it be the culprit?
Plugs are good and only have a trace of white since I think bike is running a tad lean since I put the K&N filter and 4/1 exhaust.
Or the coils? anyone hear of new Dyna coils suddenly shutting down?
At a loss here, anyone ever hear of this kind of shit happening?
Any tests anyone can think of I can do to figure this one out.
I have the full real Shop manual for bike but sadly it doesn't know either.

thoughts anyone???

I'd be tempted to look in the area of the megaphone for an intermittent blockage! Sounds unlikely I know. Your picture looks North of Edmonton - a long way off?
Regards, Art

The coils would be my guess too. Even though they are new, a bad one could still be the culprit. I don't know a way to test for it though. Maybe a exterior electricity tester?

Since it's so small, maybe carry one on you, and if the problem presents, test the coil wires. It's the only thing popping into my head.
If that's not the problem, I'd be interested in hearing what it actually is!

I was having some intermittent misfires with my 750 not too long ago. After much testing, it turned out to be that the ic igniter was going bad on me. I would run through all the checks on your electronic ignition to see if the problem lies there.

mac0239 wrote: ... 79 KZ1000st... losing power intermittently... riding along and suddenly it feels like 2 or 3 cylinders shut off and bike barely can do 30-40 mph and won't idle. Then whether you pull over or stop or try and keep riding it fires back up in anywhere from 10 seconds to several minutes of this near engine stall out...Dyna DC1 3 ohm coils (green ones)...feels like someone pulled a couple plug wires off while you were driving then after a minute or so they stick them back on....

If not already done, would assure integrity of ground connection (1) from the igniter and (2) where negative battery cable attaches to rear of engine.

Assure integrity of wiring connections through the connector that's located between pick-ups and igniter. (Perhaps loose or corroded.)

Assure sufficient clearance between screw heads (at coil primary terminals) and the coil mounting spacers. (Possible intermittent short.)

Possible fuel starvation due to insufficient tank venting. Could test run with the cap loose.

Assure valve clearances within specs.

Good Fortune!

As Patton suggested, check those valve clearances, might have tighten after the build.
Double check you plug wire resistance with a good Ohm meter.
Ohm test your Pick-up coils, and Ignition coils.
Move the clip on your carb jet needle, 1 notch, and go up a couple main sizes.
Again as suggested, those Dyna's mount with the Primary posts quite close to the bracket, could be shorting there.

10 minutes some days 20 minutes of riding other days I would lose cylinder 2-3 after setting anywhere form 3-10 minutes it would seem to be fine some days i would ride for an hour and right before I put it up it would act up. I started jiggling plugwires found loose cap on a plug, had a plugwire that didnt seem like it was on solid but repairing that didnt help. found my problem while sitting on the side of the road whith it stalled. My wiring is a little bird nesty under the tank and the bullet connecter would compress with the tank on and would occasionally not make good contact. almost ordered a set of new coils before I found it. when I would pull the tank everything was plugged in and by the time I did and would run fine until i rode for a while.

Check the double bullet style connecter it was my gremlin

Art, the pic is on the "Highwood Pass", legendary beautiful ride from Longview to Canmore hitting 8200ft altitude. The bike ran super at this altitude as well which impressed me.
Thanks for the tip.

Wow, as I expected, a ton of great leads to work on to find the gremlin.
I was tipped off by bike shops on the Fuel cap seal possibly not not venting so I tried popping it open now and then while riding and also right away when the stalling started, made no difference so scratched that one off list

The problem started before I had my valves re-adjusted 2 weeks ago. Even though 6 valves were off and needed adjustment & shims, the problem persisted.The bike did run a lot stronger after valve tweaking though, ran really really well!

I have a feeling the lose wire or dying ignition is where I will find this gremlin and will check every wire and bullet connector I can. I checked the plugs and caps and wires couple times now and they appear perfect. Didn't use ohm meter though so will try that to be sure.
Since I posted I talked to an old Kawi guru who gave me some ideas on checking to see if I have a bad coil too.

To me these little phantom problems are really the ONLY downside of old bikes. I guess it forces us to learn more about our machines and when we finally figure it out it make the ride on a classic all that much sweeter. Will post what ever it is that I find... hopefully soon !!

cracks in coils?

Chaotic Reason wrote: The coils would be my guess too. Even though they are new, a bad one could still be the culprit. I don't know a way to test for it though. Maybe a exterior electricity tester?

Attachment Non-Contact-Voltage-Tester-with-Buzzer-and-LED.jpg not found

Since it's so small, maybe carry one on you, and if the problem presents, test the coil wires. It's the only thing popping into my head.
If that's not the problem, I'd be interested in hearing what it actually is!

will those read dc voltage?

www.amazon.com/gp/aw/d/B000646OGY/ref=redir_mdp_mobile

This one does.