No spark

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Re: No spark

LukeM
Administrator
Continuity light will work fine for setting the static timing.  The timing light will help with the final timing setting, and to verify the advance mechanism is working right.

If you have a copy of the Factory Service Manual for your bike, it should spell out the procedure for you. I don't have any experience with the SOHC model you're working with, but the process should be about the same.

Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
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Re: No spark

jamman18
In reply to this post by LukeM
Well, I got the new points on and adjusted....still no spark at the plugs and as far as I can tell with a voltmeter, no power at the points either.  Where should I go from here? Plugs are good. After adjusting the points gaps I turned the crank to the "F" mark for timing and the 1-4 point was just opening at that time. But still no power.
Phil. 4:13 " I can do all things through Him who strengthens me"
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Re: No spark

jamman18
In reply to this post by LukeM
So I got the new points on and gapped but still no spark at plugs and seems to be no power to the points via voltmeter. What should my next step be?
Phil. 4:13 " I can do all things through Him who strengthens me"
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Re: No spark

LukeM
Administrator
Unless I'm missing something (which happens), this is looking more like a wiring issue, or something else is broken.  I'd suggest going back to the wiring diagram and tracing down where the +12v goes.  Might be a broken wire, or perhaps a bad coil (maybe both).  It could also be a broken or missing ground: without a good ground connection, everything would look the same (open circuit).

Sorry you're having all this trouble, but these machines are simple enough.  It's also harder to troubleshoot these over the Internet.  Is it possible you could find a motorcycle mechanic locally to look at your bike?  Maybe buy him/her a couple of beers or a nice dinner in exchange for looking at your ignition issue.

Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
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Re: No spark

jamman
In reply to this post by LukeM
Well, I had some friends help me and found that there is continuity to the low side of the coils.  Question is, do the spark plug wires detach from the coils or are they integrated into them?  I want to check them for continuity.
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Re: No spark

sgtslag
Continuity does not mean you've found the problem...  In a previous post, someone advised you to start at the beginning, or the end, of the circuit -- that is incorrect.  Divide the circuit in half, and look for voltage.  If present, then the fault/open is in the latter half of the circuit:  divide in half again, and keep dividing in half, until you can't divide it anymore -- you will have found the problem.

If you have continuity at the coil, but no voltage (low voltage side of the coil!), then you have learned only that you have no voltage at that point in the circuit.  The problem is then before the coil.  Divide the circuit in half, and measure for voltage:  if present, go back towards the coil, by dividing the circuit in half.  If the voltage is not present, divide the circuit in half towards the battery, and measure.

By dividing the circuit in half, you will find the fault within less than typically 10 steps, usually around five steps.  Continuity is not the same as voltage present:  the battery provides voltage to the points, which send it to the coils, which amplify the voltage (current is reduced, yielding the same amount of power overall) to create a spark across the plug's gap, which ignites the fuel.  You should have a simple 12 Volts running throughout the circuit to the primary windings on the coils.  Find out where the voltage disappears, and you will have found the problem in the circuit.
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII
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Re: No spark

jamman18
Ok, so I checked the continuity on the low side of the coil by disconnecting both connecters and sticking the probes on each side of the connection. To check the voltage at the same spot do I attach probes in the same manner and then just turn on the ignition or do I need to actually be running the starter as well in order to see any voltage reading?  Thanks for the help!
Phil. 4:13 " I can do all things through Him who strengthens me"
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Re: No spark

jamman18
In reply to this post by sgtslag
Ok, so I disconnected the connectors to the coil to check the continuity on the low side of the coil and I attached the probes to them to get reading. Do I do the same thing to check for voltage or do I need to have the power just on or actually run the starter as well? Thanks!
Phil. 4:13 " I can do all things through Him who strengthens me"
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Re: No spark

sgtslag
You need to measure voltage between whatever point, and ground/chassis:  place the black lead on a bare metal part of the engine block; place the red lead on the point you want to test for voltage.  Yes, you do need the key turned on -- it is the master switch that controls power to the bike's many circuits.  Pressing the starter may, or may not, be necessary.  There should be power to both coils as this design sparks on the exhaust cycle of two, of the four, cylinders.  Power will break as the points break.

Your best option is to turn over the crankshaft by hand, with a wrench on it, while the key is turned on.  This will rotate the mechanical points system, opening/closing them, which should show voltage at some point during the crank's cycle.

Again, divide your circuit in half, on the schematic.  Is there power in the middle?  Yes:  then the problem is after that point (away from the battery, the power source) in the schematic; divide in half again, and measure for voltage.  No:  then the problem is in front (nearer to the battery, the power source) of the schematic; divide the circuit in half, and measure for voltage.

Continuity in the coils indicates that they are not open; they could be shorted, but that is doubtful.  Other than that, continuity in the coils really doesn't help you solve your problem.  It is a lack of continuity, somewhere in the circuit, but in order to find out where, you will need to divide the circuit in half, repeatedly, until you are down to the component/wire/junction that is failing/open/shorted, or whatever.  Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII
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Re: No spark

jamman18
Seems like what I find is continuity on the right side (yellow wire) of the coil and nothing on the left (blue wire). This would go along with the "clicking" sound I heard near that area for about a week before it pooped out. Bad coil, seems to me.......
Phil. 4:13 " I can do all things through Him who strengthens me"
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Re: No spark

LukeM
Administrator
If that is true, and if you can reach the input connection/pins, you can use an ohmmeter across the coil leads (the blue and black or yellow and black connections).  If the coil is open, the resistance will be very large.  If the coil is not open, the resistance will be between 0 and 5 ohms. You can do the same on the output side, should you choose to do so.  The resistance on the output side of the coil will be much higher than on the input side.

If the coil indeed is open, then replacing it with a new one or one that's known good should take care of the problem.  I would recommend EBay, a reputable motorcycle junkyard, or a dealer.

In this instance, the ignition coil takes a low voltage, fairly high current level on the input side, and transforms it to a very high voltage, very low current on the output side.  The change in voltage and the time of the change of voltage on the input side determines the output voltage and length of spark on the plug.

Sorry for the wordiness, but sometimes understanding what components do helps diagnose them when they don't do.

You're getting closer...almost there.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
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Re: No spark

jamman
Actually, my mistake as I checked them again I found that there was a good reading everywhere except for the blue wire going back toward the points. I had the wires disconnected just before the coil....
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Re: No spark

jamman
In reply to this post by LukeM
To be very specific on my readings, with the meter set on X100K the needle jumps across to the far right which is 0 except the disconnected blue wire going back to the points which the needle did not move. Got readings through the coil on both sides as well as a reading on the yellow wire back to the points.
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Re: No spark

jamman18
In reply to this post by LukeM
I got the new coil ordered off Ebay and am waiting on delivery.....
Phil. 4:13 " I can do all things through Him who strengthens me"
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Re: No spark

andrew
In reply to this post by jamman
check the condensers screwed on to the points behind the chrome cover on the right side they go bad sometimes.
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Re: No spark

jamman18
I checked them and I get a big spark so they should be fine
Phil. 4:13 " I can do all things through Him who strengthens me"
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Re: No Spark Update

jamman
In reply to this post by andrew
Well, I got the new coil yesterday and installed it today. It fired right up and I ran it for about 5 minutes before shutting it off. Watched the points spark as they opened up so all was well!  Then after another 5 minutes I tried firing it up again and this time it was a no-go!  Now I have no spark at the points, voltage at the black coil connector for the yellow (right) side and no voltage at the black connector for the blue (left) side of the coil! What gives! I just totally don't get this! Anyone have any thoughts as to what I should be looking for or am  missing?
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Re: No spark

jamman18
In reply to this post by andrew
How would you suggest is the best way to check the condensers?
Phil. 4:13 " I can do all things through Him who strengthens me"
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Re: No spark

LukeM
Administrator
A condensor is the same as a capacitor.  It resists a change in voltage by absorbing or discharging its electrical capacity.

So, to test them, you can do the following:
If you have a VOM, set it to the OHMS scale, maybe at the 2000 ohms scale.
Discharge the condensor by touching the end of the wire (usually green) to the metal case of the condensor.
Put the negative lead on the metal case.
While watching the meter, touch the positive lead to the wire end.

You'll see the reading go to zero quickly as the condensor charges up, and then falls pretty quickly down as it reaches its capacity.

Here's a good link:
http://www.youtube.com/watch?v=5LUak8v3OU4&feature=related

The alternative would be to just replace them.  You should have gotten a condensor with each set of points, and anytime I swapped points I'd swap the condensor as well.  Cheap insurance.

Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
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Re: No spark

jamman18
I am one BIG novive when it comes to electrical....on your instructions could you tell me what color wires I am using for each step precisely?
Phil. 4:13 " I can do all things through Him who strengthens me"
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