TOPIC:

One of 2 new coils on my KZ750F burned through after less than month. I suspect a ground issue. Can you guys tell me how exactly you ground them? I had 1 ground cable go from only one screw at the right coil to the frame (beside the regular negative connection at the coil. I gonna take a picture of that quick but I would like to know how it is supposed to be. This bike is a freaking nightmare..... Now that I think about it, I also killed a new starter relay and the cable of the headlight burned through. So it have to be the ground or not?

The Factory installs them like that. Bolted to the frame, with a ground wire under just one screw of one coil. Never seen it any other way on my KZ's.
With all the other electrical issues you state. You need to verify charging output voltage. Check the output across the battery terminals with a volt meter and rev the engine to 4K RPM. Should be in the middle 14v range, not 15+.

Yep, maybe 14.5 volts DC. max, anything more, and many electrical items will be at risk.

The coils, themselves, don't need to be electrically grounded to the frame or anywhere else.

The high tension wires are only incidentally grounded by virtue of the fact that the high tension circuit uses the head to get the current from one plug to the other. But the fact that it's grounded to the battery does not matter.

The primary side of the coil gets grounded through a switch (points or transistor), but is not permanently grounded.

very interesting. thank you! on which setting exactly the multimeter have to be? my neighbor got one.

also, what do i have to do if the voltage is too high?

That ground wire, if bolted to the frame of the coil, is still needed, but it's not for the coils, it's for other items on the bike. It just happens to use a coil mounting bolt. So it needs to remain.

If the voltage is too high, then check the voltage on the brown wire at the regulator/rectifier. Use the battery's negative post for reference. That means the meter's black lead should be on the battery's negative post.
If the brown wire matches the battery voltage, and both are above 14.5v or so, then the regulator may be bad.

Also, check the ground. Make sure the black wire on the reg/rec is not more than about 0.5v.

ok great. will do as soon i get a multimeter. the guys on ebay i bought the coil from offered me so send a replacement for free even though i was planning to pay. btw, i found a good deal a set of 2 coils for $65. let me know if anybody needs the link.

element303 wrote: One of 2 new coils on my KZ750F burned through after less than month. ..... Now that I think about it, I also killed a new starter relay and the cable of the headlight burned through. So it have to be the ground or not?

First thing to check is if the voltage regulator has failed and is letting the system voltage go too hih. With engine at 3000 RPM, battery voltage should be 13.5 - 14.5V. If it is higher, that is what's killing your parts.

I would like to set this bike on fire...

After another 4 days being stuck I got the coils with express mail today. Installed the one that didn't fire. NOTHING... Checked cables. Checked spark plugs. Exchanged connections of could.. Nothing. It only seems to affect the left coil but none of the 2 new ones fire. Lasty thing I did was checking the caps of the spark plug cables, they were old. Turns out I have spark when I use the caps of the "good" coil. Driving on 2 cylinders to the next motorcycle shops and buying 4 new caps and again spark plugs and waste another $50 bucks and ... unbelievable still no spark on 1+4..... Yes, i changed the spark plugs cause I know they were wet with new ones and still nothing. I was so pissed off that I didn't even check anymore when I got home and now its dark. This doesn't make any sense....... Any ideas?

Plugs 1 & 4 fire off the same coil. You need to go to the coil and work backward. Get your multimeter handy, set it to 20 DC Volts
Remove the tank so you have access to the coils. Examine both coils. They have two spade terminals each with a wire connected to it. One of the wires will be the same color on each coil This is the 12V which is constantly on when the ignition is on. Turn the ignition switch to ON. Use your multimeter to verify there is roughly 12V on these wires. Put those connectors back on. Remove the other connector on the 1-4 coil. This is the one that receives the trigger voltage that tells the coil when to fire. Put your multimeter probe on that wire and press the Starter button. That wire should pulse from 0 to ~12V or so, periodically, as your ignition system tells the coil to fire. If it does, the coil is probably bad. To test that, switch the coils. If the 2 & 3 cylinders do not fire, it is following the coil and the coil is bad.

i did all that without multimeter. The coils are brand new, sp were the ones I had installed but the problematic coil (side) had the coil burned. SO I expected it to be the coil. But the new one won't work. I checked the cable that gives the pulse. Everything seems fine there. I will test everything again now.

The one thing that I found out was if I use the plugs for the cables from the "good" coil, it would fire. So i went to the store to buy new plugs for the cable but when installed - still nothing.