KZ650 Engine start troubleshooting

F64 wrote:

I can't remember if points are supposed to spark. 
It may be a sign of a bad points condensor.

A small amount is ok but the purpose of the condensor is to reduce arcing so if it's much then it's probably bad !

Wookie58 wrote:

F64 wrote:

I can't remember if points are supposed to spark. 
It may be a sign of a bad points condensor.

A small amount is ok but the purpose of the condensor is to reduce arcing so if it's much then it's probably bad !

Okay, so when doing the test tonight, I'll also clean the point with a file and thinner. That can't hurt. And if I still see consistent sparks at the points, i may have to change the condensers.

See what test results you get before you change anything (400 grit emery paper is best for cleaning the points)

Okay, so I cleaned the points a little bit with 400 grit emery paper and did the tests.

• When connecting the red lead of the voltmeter to the battery positive, and the black lead to the power supply of the coils (red/yellow), with ignition and kill switch on, i get around 2.7V. Not 0.5V!!
• When moving black lead to the black (and then green) wire of the coil, I get again 2.7V with the points closed, and battery voltage (12V) when i pry the point open. Same for both side.

I must admit that I have not clue what that means...

Rideallyear wrote:

Okay, so I cleaned the points a little bit with 400 grit emery paper and did the tests.

• When connecting the red lead of the voltmeter to the battery positive, and the black lead to the power supply of the coils (red/yellow), with ignition and kill switch on, i get around 2.7V. Not 0.5V!! OK, what this is telling you is there is a difference of 2.7v between the battery and the coils (max should be 0.5v) this is caused by a significant resistance between the fuse box and the coils (most likely suspects are ignition switch or kill switch) You can use the process in my fault finding guide for "resistance faults" to pin point the issue (should only take 3 or 4 pokes with a voltmeter to identify) - to eliminate everything else you could run a jumper wire with a 10amp fuse in it from the battery positive to the coil feed wires and see if she starts (just as a test)
• When moving black lead to the black (and then green) wire of the coil, I get again 2.7V with the points closed, and battery voltage (12V) when i pry the point open. Same for both side. This makes absolutely no sense - when the points are "open" I would expect to see the same voltage on both sides of the coil (2.7v)  as the circuit is broken - when the points are "closed" the black/green wires are grounded through the points (the points breaking the ground is what causes the coil to spark) so with the red meter lead on the positive battery post I would expect the black meter lead to see ground and read battery voltage !!!!!!

I must admit that I have not clue what that means... No worries

Thanks much. I'll go find the culprit for the resistance fault. I tested many time because I thought i did it wrong, but it always came back to 2.7V. I restored the controls on the handlebar recently, so maybe I somehow induced more resistance somewhere.

For the second test, i'm the dummy! I crossed MY wires walking back from the workshop to the computer. It should have read:

• When moving black lead to the black (and then reen) wire of the coil, I get the battery voltage (12V) with the points closed, and again 2.7V when i pry the point open. Same for both side.

But here is the good new. Somehow, after cleaning the points and playing with the wire connectors of the coil, I somehow started to get a sparks on cylinder #1 and #4 (and thus most likely the other ones). It took a few tries and some starting fluid, but she started!

So i'll try tomorrow again, chase the resistance fault and move onto the next issue: running rich.

I did think that might be the case 

I'm happy to report that my KZ650 is now starting on the first try, every time!
The cleaning and adjustment of the point did the trick. The sparks are now super small on the points.
Two days ago, I rode 45 min (at 25F mind you) to my local shop. Talking to the mechanics, he said that the condenser may slowly going bad, but not to worry about it now. 
I guess I'll stock a condenser for the day it becomes a problem.

Thanks for your precious help, as always!

I would still look to resolve the volt drop on the feed side of the coils - the longer the motor runs the bigger the drop will get. This is because a resistance generates heat which further increases the resistance (may become a “hot start” issue?

Thanks Wookie! Yes finding the volt drop is still on my to-do list.
The bike is at the shop now as it needed a carb sync (which is something i want to learn how to do). This has resolved the backfiring issue I had. But the bike is still in the shop as i'm waiting for a set of carb holders (one was cracked).
Once i get the bike back home, i'll look that the volt drop. Since I refinished the handle bar controls, I may have messed up something. But is your experience, what in the switch would create additional resistance?

 

Rideallyear wrote:

Thanks Wookie! Yes finding the volt drop is still on my to-do list.
The bike is at the shop now as it needed a carb sync (which is something i want to learn how to do). This has resolved the backfiring issue I had. But the bike is still in the shop as i'm waiting for a set of carb holders (one was cracked).
Once i get the bike back home, i'll look that the volt drop. Since I refinished the handle bar controls, I may have messed up something. But is your experience, what in the switch would create additional resistance?

 

I know I keep banging on about my "guide" but the processes contained really are the most efficient way to "diagnose" electrical faults (it's the same methodolgy we teach VW, AUDI, Jaguar, Landrover etc dealership techs)  once you have access to the plugs for the ignition switch and the handlebar switch it should take 15-20 mins to pinpoint. With the regards the kill switch, if it is found to be the issue, the contacts are pretty robust so if I had to take an educated guess I would suspect one of the 40+ year old soldered joints (soldered joints do rot over time)

Keep banging. It is a good piece and the concepts and procedures are clearly explained. I recently used it to coeectly diagnose our church's well abused John Deere that ended up having three electrical faults at once.