TOPIC:

The bike jerks when I've been going for about half an hour, it starts to run out of steam until it finally stops. Then I let it "cool" for a while (like another half hour) and it works again.

I'm almost sure it's a thing of the ignition coil, and actually even if it isn't, I've read so much about the bad of the old coils and the good of the new ones that I already want to change it yes or yes.

I have read about Dynatek coils, good reviews. But I don't know which one I should put on it considering that I use a Tytronic electronic ignition (the cheap copy of the one from Charlie's Place) and apparently electronic ignitions need "faster" coils (less resistance) than point ignitions.

Can someone guide me?

Go to the Dynatek website and use their selection system to input your bike year, make and model.  It will select the correct coil.

and that was the first thing I did, but my bike simply does not appear.
I know someone on this forum put a Dyna coil on a KZ400 (so one of the models they have for other bikes must work for mine) but I think it's no longer active so I can't ask them.

Since the op is running an aftermarket ignition, he needs a coil with the proper resistance for that system, not the factory system.
Does the paperwork that came with the system, or the company website state what resistance is needed?

Also, your problem may be elsewhere. Does the bike have a fuel filter that could be partially clogged up causing fuel starvation?
Is the fuel tank vent clogged?
Is the fuel line really old or really cheap? It could be delaminating inside, causing fuel starvation.
Have you recently done some work on the bike that might have kinked the fuel line?

I looked at the parts diagrams for a KZ400 ignition.  OEM used points and a single coil.  If your coil is original you can determine which one to buy by measuring the resistance on the primary side of the coil.  The primary side would be the two wires on the coil.  Secondary would be plug wire to plug wire, but you want to know the resistance on the primary side.  I'm guessing it will be between 3 and 4 ohms.  In that case, you want to buy a coil with 3 to 4 ohms primary resistance.  The Dynatek coil is green in colour, with two outlets for plugs.

wrote:

Since the op is running an aftermarket ignition, he needs a coil with the proper resistance for that system, not the factory system.
Does the paperwork that came with the system, or the company website state what resistance is needed?

Also, your problem may be elsewhere. Does the bike have a fuel filter that could be partially clogged up causing fuel starvation?
Is the fuel tank vent clogged?
Is the fuel line really old or really cheap? It could be delaminating inside, causing fuel starvation.
Have you recently done some work on the bike that might have kinked the fuel line?

New fuel filter and petcock, upgraded epoxy coated fuel tank, new fuel lines, clean carburetors, etc. But someone said it's better to rule out electrical problems first before anything else and I try to work that way.
The ignition system is a copy of Charlie's Place. Some basic assembly instructions and nothing else at all. I could write Charlie to ask him what coils he uses with his ignition, too (I didn't think so)

wrote:

I looked at the parts diagrams for a KZ400 ignition.  OEM used points and a single coil.  If your coil is original you can determine which one to buy by measuring the resistance on the primary side of the coil.  The primary side would be the two wires on the coil.  Secondary would be plug wire to plug wire, but you want to know the resistance on the primary side.  I'm guessing it will be between 3 and 4 ohms.  In that case, you want to buy a coil with 3 to 4 ohms primary resistance.  The Dynatek coil is green in colour, with two outlets for plugs.

I think the original coil is 4 ohms, but I read somewhere that lower resistance coils (maybe 3 ohms) are better for electronic ignition. I wanted someone who knows it for sure to confirm it for me.

Do you have the link (or model number) for that green Dynatek coil? To take a look.

Thanks for your time.

Did the aftermarket ignition say it works with stock coils? 

Like Tex said look to the fuel system. More times than not at least here guys that have symptoms like you find out it fuel starvation. 

I run the green coils on my Z1 and KZ1000 with electronic ignition.  (Dyna). They are listed on the Dynatec website as 3 ohm coils.  My original Z1 coils were 3.8 ohms.  The KZ1000 had 1.9 ohm coils with a ballast resistor.  When I went to the green coils on the KZ1000 I eliminated the resistor.

I had a Yamaha 400 Maxim that would do the same thing, Ran great for 30 minutes then would loose power. I could keep it running and limp home at 30mph.
It turned out to be a bad igniter box. I would suspect the Tytronic electronic ignition is breaking down. 
I

I had that problem on my KZ1000 too.  Two cylinders would drop out intermittently.  The coils were fine so I assumed it was either in the exciter or the electronic pickup.  

Make sure the tank breather is not clog..that’s what it sound like.