Got spark but won't start

If not already done, would check to assure:

Points on left-hand side (9 o'clock) -- are wired to ignition coil that's firing both outside spark plugs (cylinders #1 and #4).

Points on right-hand side (3 o'clock) -- are wired to ignition coil that's firing both inside spark plugs (cylinders #2 and #3).

Points cam rotor is installed correctly (and not 180 degrees out) -- may be done by assuring points on left-hand side (9 o'clock) just begin to open as F mark for 1/4 on advancer aligns with timing mark on engine case.

In the example of points shown below, the black wire goes to whichever coil fires outside spark plugs, and green wire goes to whichever coil fires inside spark plugs.

Good Fortune!

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I don't have any gauges to do a compression check. Is there another way to check?
Also, one thing I've noticed is that the right side coil wires seem to be really tightly stretched to reach the 1 and 4 cylinders. Is that normal? Seems like they should be longer. They're mounted really close to the motor too.

TeK9iNe wrote:

Make sure the engine to battery ground is excellent. (Via nice thick wire).

If your getting spark (and it is properly timed), then all you need is compression and a close enough ratio of fuel and air.

1. Make sure timing and firing order. 10 degrees before top dead center, on the F mark of advancer for idle.

2. Do a compression check. All the cylinders need at least 90+ pounds of compression to run fairly smooth, and they should be within 10% difference of eachother.

3. Turn your mixture screws out 2 turns and turn the idle screw in to increase idle 3 times.

Full choke, and no throttle. Crank bike for about 4 actual seconds. Count them, 1 mississippi...

Sometimes the advancer is installed backwards/coil signal wires crossed. Usually you will get a seriously loud afterfire warning you of this.

GL!

Here, the F mark is for outside spark plugs in cylinders #1 and #4.

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"right side coil wires seem to be really tightly stretched to reach the 1 and 4 cylinders"...

Right side coil OEM is for 2/3 cylinder/sparkies....
Granted, it can be either way as long as wired correctly off ignition plate.


Follow the link to download KZ650 model wiring diagrams....

diagrams.kz650.info/wiring/WiringDiagrams.htm

Out of all the wiring diagrams for KZ650 I found (20 each) only one had a 4 conductor ignition switch!...

diagrams.kz650.info/wiring/images/KZ650-B1.jpg

For your model, then Brown and White conductors would be the correct terminations for passing voltage to the control switch onto the coils. This may be where your problem lies...

Measure the voltage at this RED box location, should have +12Vdc or higher on a good charged battery...

NOTE: The brown conductor is fed off the regulator, what is this voltage measurement?

Another thing you can do to get this old girl started...
Again, this is for trouble shooting your issue, not as a permanent fix...

As already mentioned, insure you have a ideal frame/engine ground to the battery (-) terminal.

Off the battery, inline 20 amp fuse through a SPST switch.

Remove the quick disconnect yellow/orange as in the RED box and terminate to the other side of the switch.

The starter still receives the ignition battery voltage but the coils are receiving directly off the battery...

If this works then if brown feed is indeed +12Vdc or higher, then problem (voltage drop) in handle bar control housing/engine stop switch!

Or.... To bypass hand control altogether....

If good use the white conductor (battery and fuse) and connect to switch lead. Remove the quick disconnect yellow/orange as in the RED box and terminate to the other side of the switch.

In either case, this would pass battery voltage directly to the coils... Again, only going to work if frame/engine ideally grounded, battery voltage +12Vdc or greater, points/condenser, electrical charging rectifier/regulator system are good and compression/cam alignments are set correctly...

let us know how it works out for you....

OMR

Regardless of advancer style, are concerned with F mark when dealing with ignition timing. And not the T mark which is top dead center and used for other things such as cam timing.

Good Fortune!

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Thanks so much everyone. You've provided me with some great info (especially the correct wiring diagram). It does seem to act like the kill switch is on, so I think I'm going to order a new ignition switch first and take your suggestions from there to work my way through it. The only problem is that all the ignition switches seem to be a 6-pin. I'm guessing I could make one work. Just need to figure out which two wires to pull out of the connector (guessing it's probably going to be a blue for headlight and something else).

btkz650 wrote:

...some great info (especially the correct wiring diagram)....

As likely already known, click on the diagram to enlarge and enhance visibility.

Good Fortune!

btkz650 wrote:

Was wondering if anyone could help out a newbie. I'm working on a 78 KZ650 bobber project and got her all together and mostly wired up. I have spark (seems pretty weak to me though)...

...right side coil wires seem to be really tightly stretched to reach the 1 and 4 cylinders....

...does seem to act like the kill switch is on....

Old Man Rock wrote:

...Right side coil OEM is for 2/3 cylinder/sparkies....
Granted, it can be either way as long as wired correctly off ignition plate....

does seem to act like the kill switch is on --- supposed to be no spark with kill switch in OFF position.

Right side coil OEM is for 2/3 cylinder/sparkies --- is oem position of coils on large fours, but was thinking opposite on oem KZ650 with right side coil for 1/4 and left side coil for 2/3.

can be either way as long as wired correctly off ignition plate --- Yep!

Good Fortune!

The coils were switched on mine. The black wire was connected to the inside plugs 2 & 3. I switched the black and green wires at the coil quick connect so they would be correct and still doesn't even act like it wants to start. I'll check the F mark and get back to you.

Patton wrote:

If not already done, would check to assure:

Points on left-hand side (9 o'clock) -- are wired to ignition coil that's firing both outside spark plugs (cylinders #1 and #4).

Points on right-hand side (3 o'clock) -- are wired to ignition coil that's firing both inside spark plugs (cylinders #2 and #3).

Points cam rotor is installed correctly (and not 180 degrees out) -- may be done by assuring points on left-hand side (9 o'clock) just begin to open as F mark for 1/4 on advancer aligns with timing mark on engine case.

In the example of points shown below, the black wire goes to whichever coil fires outside spark plugs, and green wire goes to whichever coil fires inside spark plugs.

Good Fortune!

[Click on image to enhance view.]

I now have the black wire from the "9 o'clock" side of the points going to the inside #2 & #3 cylinders and the green going to the outside cylinders #1 & #4 (sitting on the bike the left cylinder is 1 going to the right to 4). - Check.

The old plugs were slightly black (but not sooty), so I put a new set of plugs in just to be sure. It did improve the spark. - Check.

The left side points start to open when the "F" mark is slightly to the right of the timing mark on the engine case. - Check.

Then I tested the voltage at the coil quick connect. The highest reading I could get (even with my trickle charger on the battery) was 11.75. The most I ever got out of the battery was 12.83 (with the charger on). It was 11.63 without. - Oops, that doesn't look good. Then I touched the coils and both of them were smokin' hot. Could this be the problem? Bad battery and are my coils fried or did they get that hot because I had the trickle charger on while trying to start it? Are these that sensitive that they won't even act like starting with less than 12v at the coils? I've started other bikes with weak batteries before.

I decided not to open up the carbs yet until I ruled out any electrical. Guess I'll get a new battery and start over.

btkz650 wrote:
I now have the black wire from the "9 o'clock" side of the points going to the inside #2 & #3 cylinders and the green going to the outside cylinders #1 & #4 (sitting on the bike the left cylinder is 1 going to the right to 4).

Nope, sorry bt, but that's wrong, because black wire from the "9 o'clock" side of the points should connect to whichever coil has its plug wires attached to the outside spark plugs in cylinders #1 and #4.
And green wire from the "3 o'clock" side of the points should connect to whichever coil has its plug wires attached to the inside spark plugs in cylinders #2 and #3.

The old plugs were slightly black (but not sooty), so I put a new set of plugs in just to be sure. It did improve the spark. --- Very good idea.

The left side points start to open when the "F" mark is slightly to the right of the timing mark on the engine case. --- Okay, provided it's the "F" mark for 1/4 and not the "F" mark for 2/3. Ignition timing may be slightly retarded, but may be fine tuned later with a timing light on running engine.

...voltage at the coil...highest reading...was 11.75...battery was 12.83 (with the charger on)...11.63 without...touched the coils and both of them were smokin' hot. Could this be the problem? Bad battery and are my coils fried or did they get that hot because I had the trickle charger on while trying to start it? Are these that sensitive that they won't even act like starting with less than 12v at the coils? I've started other bikes with weak batteries before. I decided not to open up the carbs yet until I ruled out any electrical. Guess I'll get a new battery and start over. --- the 11.75 ought to be enough to start and run, especially if using a kick starter and no lights on.

The heat could be from allowing power continuously to the coils while the engine isn't running. For whatever reason, such as faulty wiring, or neglecting to turn off the ignition switch. Could finesse this issue by disconnecting battery or connectors supplying power to coils whenever not actively attempting to start the engine.

Meanwhile, would be okay to jump bike battery from known healthy car battery (car engine NOT running), but only while actively attempting to start the bike engine.

An important first step is to assure the wiring from points to coils is correct. And that coils are receiving power only while actively attempting to start the engine and while the engine is running.

Would also clean and gap points, and then re-time statically with an ohmmeter or in-line test bulb to assure point contacts are opening precisely when the correct F mark aligns with the case timing mark.

When hand turning the crankshaft to align the F mark, always use the "fake" 17mm nut. Never use the smaller bolt head appearing at end of crankshaft, because it will easily break off leaving remainder of bolt tightly wedged inside the crankshaft.

As known, the points serve to rapidly ground and un-ground the ignition coils at precise moments during crankshaft revolution.

Once there's a healthy blue properly timed spark at all plug tips. Then it's time to assure acceptable compression and valve clearances being to specs.

After that comes adequacy of fuel supply, assuring proper fuel level in float bowls, and finally addressing carb cleanliness, tuning and adjustments.

Good Fortune!

[Click on image to enhance view.]