Dies after warmed up

Was gonna put this in the electrical section but Don’t wanna rule fuel out just in case.
This will be my second experience of this encounter with my bike. First being while getting gas a week ago. Started the bike up and let it idle for a bit. While doing so, I took a look at my fuel line and noticed that every time I gave a little rev, I’d see little bubbles floating up. but otherwise a full of fuel line. Also while holding revs at like 1300-1500 heard a knocking noise that sound like it was coming from the advancer area. So I go and grab me an allen to pull the cover then just as I got back to the advancer side to loosen the 2 allens, the bike dies as if I used the kill switch? So I quickly looked at the fuel line, that’s still full. Didn’t have my seat off so was only able to feel my coil and reg/rec. Coil was cool to the touch. Reg/rec seemed it’s normal warm temp shunting at idle. Tried to restart, but just cranks. After 10mins or less, restarts just fine. Haven’t tested if it’ll do the same thing after a restart, but I’m just gonna assume it would?
I’m pretty certain it’s electrical, now just gotta figure out which 35+yo part it is? Which should I test first and procedure. But first and foremost, I need to get a battery for my volt meter. Any ideas would be greatly appreciated. Thanks forum..

I assume you still have points.

For testing only, you can just run a hot-wire from the battery positive to the coil's positive side. Also make sure to turn on the ignition switch to make sure the charging system will be working (so you don't kill the battery).

That will bypass almost all of the electrical stuff on the positive side. The only thing left is the wire from the coil to the points, and the ground wire from the engine to the battery.

Make sure you pull that "hot-wire" when the bike is not running or you can cook the coils.

If it still dies out, and it's electrical, that narrows it down to the battery, coil, and points or the wire between the coil and points/condenser and the ground wire.

Thanks for the reply Loud, no points. Electronic ignition. So mechanical advancer, pick up coil and ignition module all of which are still original to the best of my knowledge. I’m sure your test can still be done though. I’ll get that done and report back as soon as I can.

Are the valve clearances in spec? If the valves are tight they will hang open when hot.

Nessism wrote: Are the valve clearances in spec? If the valves are tight they will hang open when hot.

Man I’m so glad I machined reliefs in the rocker housing for a feeler gauge. I remember the manual calls for .007-.009. My valves seem to be the quietest with both set to .19mm and just checked them and they’re still set. Thanks Nessism.

LOUDHVX, I just wanna refresh my memory, since I’ve got some time the next 2 days. Should I disconnect the power on the coil and use the jump wire? Also, with the jump wire, I’m assuming I should start the bike and see if it dies after warmed up? I’m usually pretty on top of 12v electrical, but I’ve been doing so much mechanical work on cars the past year, I’m a bit past rusty. Sad thing is, I’m a metal fabricator by trade?? Thanks for your help

I had something like this mess me up for weeks. Bike would randomly die when warm..Let it cool down for 15 minutes and it would fire right up.

It was the pick up coil. It would fail when hot.

I used a hair dryer to heat it up and it would fail. Then I used canned air to cool it down and it would work.
But that was just my experience...yours could be anything.
81 KZ440 D2

F64 wrote: I had something like this mess me up for weeks. Bike would randomly die when warm..Let it cool down for 15 minutes and it would fire right up.

It was the pick up coil. It would fail when hot.

I used a hair dryer to heat it up and it would fail. Then I used canned air to cool it down and it would work.
But that was just my experience...yours could be anything.
81 KZ440 D2

I’m definitely not ruling the pick up or any other ignition related part out (except maybe the hand controls cause they’re not 35+yo) When yours would fail, did you by chance hear an abnormal ticking noise, almost like a valve needed an adjustment, in that area moments before it would die? I’ll try what you did to test it when I get my carbs back together and mounted. Thanks for that info.

You can keep all the other wiring as is. Adding that jump wire is providing an alternate power path to rule out flakey switches and fuses. You should still turn the bike on the normal way,key switch and kill switch, to make sure the rest of the bike gets power.

But if you are getting that ticking sound just before it dies, it sounds like the spark is jumping to ground. The most likely cause would be a failing resistor cap or resistor plug or bad plug wire. It could be the coil too. The pickup, as f64 mentioned is a typical suspect,but in this case , because of the ticking, becomes less likely, but not ruled out.

I did not hear a loud ticking.
Your issue may be as loudhvx has mentioned with a spark jumping to ground.

Let’s assume it ends up being the pick up coil on the crank. Where’s a good source for a compatible replacement? I’m finding them at DennisKirks and that’s about it? I’m about done with the carbs. Hopefully will get the floats in and height set today but with this heat going on (it’s 96*, yeah imma wuss) I’m draggin ass with procrastination.

I bought my replacement off ebay.. That was 5 years ago. Still running.

So got the carbs back together and back onto the bike. Jumper wire in place as per LOUDHVX’s troubleshooting instructions posted. Before I use to be able to start the bike with one to two kicks. But since it sat for a bit, kick starting wasn’t happenin. But since I redid the carbs that should be able to happen again. Soooo..new gas and a few slow kicks just to prime the oil and get fuel into the holes it wants/needs to go, ignition on and I give it a kick...nothing...another kick..got a small life sign...well it started at 4 kicks. Long story short, bike died after 10mins or so at idle. Same as before. Set my meter to 2k and ohm the pulse coil first, quick display movement the nothing. Battery voltage is 13.01 ignition off 12.9. I check the pulse coil again and get a 488. Woohoo this has got to be the culprit..right? Oh and yes, pulser was unplugged when probing. If this is it, after googling I didn’t see any available that’s a direct bolt on. Only ones I’ve seen were Caltric and the base plate is not even close, but if that pulser would/can work, I can get it mounted. Any thoughts?