Topic: the 1-4 coil mystery??

[crazypj]

sooooo i decided to bridge the points for the 1-4 annnnd bingo! great spark!

excuse my ignorance what does it mean bridge the points

stick a screwdriver in there to 'bridge' the contact faces

[CB750F2]

Ok Saw you have done well. So you are loosing > then 1 volt between the battery and coil with one coil and no other load on the electrical system. Is this cottect? I am assuming that it is. The load on the electrical system due to one coil would be around 2.3amps so there must be approx. 0.5ohms resiostance between the junction of the black/white wires and battery +ve. I suggest that you clean all connections between these two points and retest. Pay particular attention to the 15amp main fuse holder, the ignition switch and the kill switch. There should be zero ohms between the BAT and IGN terminals when the Ignition Switch is ON and also zero ohms between the IGN and ON terminals when the Kill Switch is ON. Please disconnect the battery when carrying out these tests. I see in one of your earlier posts that you got spark when you ran a temporary wire between battery and the black/white wires at the coils. This is why I am suggesting these tests. Actually, before you do anything disconnect the main cables from the battery and the b/w wire from the coils, turn ON the Ignition Switch and Kill Switch and measure the resistance between the +ve battery lead and the b/w wire. Make a note of this reading then carry out the above tasks and then remeasure the resistance. If you have made an improvement reconnect and try with the starter. Also ensure that the large cable from battery -ve is making a good connection to frame.
      Other considerations
      At this point we have not considered the secondary side of the ignition coil and we have assumed that the coil is not faulty. You could remove the spark plug caps from the plug leads and place theme near the frame with about 1/8" gap and then try with the starter. The other thing that you could try is another known good coil.
I look forward to your results. Pat

[saw750]

"So you are loosing > then 1 volt between the battery and coil with one coil and no other load on the electrical system. Is this correct?"

the only other draw on the system would be the lights.

"Actually, before you do anything disconnect the main cables from the battery and the b/w wire from the coils, turn ON the Ignition Switch and Kill Switch and measure the resistance between the +ve battery lead and the b/w wire."

i will attempt this later today.

[CB750F2]

Saw, I suggest that you repeat the voltage checks with only the 1-4 coil drawing load from the battery. If you have lights running either turn them off or remove the Headlamp and Tail Light fuses. Pat.

[Bill/BentON Racing]

Turn the engine over until the points are open.With key on take a flat tip s/driver and cross the pt gap and connnect real briefly.you should see a little arcing @ points and if you have s/plug in cap and grounded it should spark. Good Luck,Bill

[saw750]

pat yes agreed. i was thinking about this after i answered your question.

i am also going to rerun the resistance test at the point post (why? because during that test i was using one them fancy "ranging" multimeters ... i am less familiar and its possible i misread the results)

[Spanner 1]

Memo to all trying to help.... RH control is not stock, start button replaced, headlight is 'on' with ignition = voltage drop due to headlight ( normal)... prolly 1-4 will spark with A) Fully charged battery and B) Headlight bulb removed or an off switch wired to it.....

[CB750F2]

Saw, a couple of more checks that you can do. Disconnect the red/yellow at the starter solenoid then redo the voltage check at the b/w wire but with the starter button pressed. The starter motor will not run and the voltage at the b/w wire should not change with the start button pressed or not pressed. You have mentioned that you have replaced this button and this check will check to see if you are loading up the circuit when pressed - it should not because because the starter solenoid has been disconnected. If it does load up the circuit - indicated by a lower voltage at the b/w wire with the button pressed - then you have found your problem. You can also confirm by connecting a temporary wire from battery +ve to the r/w wire onthe starter solenoid. Ensure that you connect the wire securely to battery +ve first so that you do not have any sparking near the battery. The starter motor will turn and then you can check for spark with the ignition and kill switches ON. Other wise continue with the checks that I suggested. Pat

[CB750F2]

Spanner, I thought that at first also but  Saw indicated in one of his earlier tests that he disconnected the head light and still had no spark. However, I agree that the starter button looks suspect - see my earlier posts. Anyway let's see what Saw finds. Pat

[saw750]

now i know why farmer ed parked this bike in his barn lol

all tests were performed with light fuses out.


1. voltage
- battery fresh off the charger 13.8 volts (that sounded a lil high to me)
- blue wire (points closed) 12.7 volts
- yellow wire (points closed) 12.6 volts
- black/white 12.2 volts (no change with button pushed and yellow/red disconnected)

2. resistance
- 1-4 points pole. wires removed - 0
- from + to b/w - 0
(started to get a lil lost at this point - i am sure there were other resistance tests i was supposed to perform but reading thru the posts- yes i got lost )

3. ran jumper from positive battery terminal to disconnected yellow/red. starter turned but no spark on 1-4

4. removed plug caps. i/8 from block. no spark

i thought i had found the issue when i discovered the connection yellow/red at the solenoid was oxidized. it cleaned up nicely. but no change


ohhhhhhh i cant wait to get to the charging system..lol ; ))

[CB750F2]

Some comments regarding your tests results:

Result 1
The voltage at the b/w wire is Ok.
The battery voltage is high because it has been on the charger and it will fall quickly to aaround 12.7 volts if the battery is fully charged and with no load.
Where di you measure the blue an yellow voltages? I assume that they were measured where they meet the b/w wire.
Result 2
Those readings are good.
Result 3
Did you have spark on 2-3?
I would like you to repeat this test and this time measure the voltage at the b/w wire while the starter is cranking the motor.
Result 4
Make sure that you have exposed wire at the end of the plug wires when you do this test - not pushed back into the insulation. The 1/8" gap needs to be from the end of the wire to frame or motor.

You could also swap the the blue and yellow wires at the points and retry for spark using the starter motor. Remember to swap back when finished.
Pat

[saw750]

result 1. you are correct blue and yellow voltage was measured at coil

result 3. yes sparks on 2-3

- test understood and will post results

result 4. i also have a spark tester. its a medieval device i used on the old triumph. its adjustable and measures spark strength...it has an open arc and if not handled correctly...is painful

5. ok

[CB750F2]

Good morning Saw. I have just re-read all of the posts and I see that at one stage you ran a temporary wire from the battery to where the b/w wire meets the coils and you said that you got spark. I also asked you to do this but you haven't fed back a result. Could you do this test please.
Your result2 of zero ohms is actually too good. There must be some resistance there because the voltage drop across this part of the circuit is approx. 1.0 volt. Maybe your meter is not reading low resistance correctly or you are on the wrong range.
I look forward to your feedback. Pat

[saw750]

hi pat. yes running a jumper from the battery to the coil did produce a spark. i will retest again.

i switched the blue and yellow wire at the points and 1-4 did spark but 2-3 did not - however i did observe spark at the 2-3 point. I performed the test twice with the same result. Switching the wires back 1-4 did not fire.

i do not like the digital multi-meter. i will retest ie unhook  the positive and measure resistance between the positive cable and b/w

i measured voltage at b/w (11.8 volts) and then ran starter. The voltage dropped to 9.8 volts-10.2 volts.

[CB750F2]

I am a little confused with your last post. You said that when you performed the test with the wires crossed at the points 1-4 coils fired but 2-3 coils did not then in the next sentence you said that you observed spark at 2-3. Please clarify. Assuming that you did have spark at 1-4 coils and not 2-3 coils with the blue wire connected to 2-3 points and the yellow wire connected to 1-4 points then there seems to something wrong with 1-4 points setup. You said earlier that you have checked the condensor by swapping and checked the contact resistance of the points. I suggest that you ensure that the condensor is connected correctly to the points, again check the resistance of 1-4 points when closed and check that you have zero resistance between the ground side of 1-4 points and the backing plate. Do this last resistance check with the points open. Keep going. Pat

[Spanner 1]

I'd love to see a close-up pic. of your 1-4 points, I'm sure Pat would too : , with the blue wire and the condensor connected..... 'cos sumtins up there for sure

[saw750]

re: confused - switched the wires: after switching the wires (yellow went to to the 1-4 point and blue went to 2-3) i pushed the starter button and saw spark at 1-4 PLUG but not the 2-3. HOWEVER At the POINTS I observed a VERY visible spark at the 2-3 point? which after a few turns of the starter disappeared. Its worth noting that when the wires were returned to the original placement that the VERY visible spark at 2-3 was present and again stopped after a few turns of the starter. (yes VERY lol ie its a strong flash)

- will swap condensers

- will check for resistance

- i will take a pict if i can find my wife's camera lol

[saw750]

ok (deep breath) i went an bought a new multimeter and redoing tests

switched condensers: there is no change. 1-4 plugs do not spark. 2-3 sparked.

measuring resistance between blue at points to blue at coil with points closed
is .5 ohms

measuring resistance at blue points without any wires attached and 1-4 point open is 0 ohms

measuring resistance between b/w wire at coil and the positive removed from terminal. ignition switch on. run switch on - the result was .8 ohms - pushing the start button made no difference.

measuring resistance from yellow/red disconnected from solenoid with ignition switch on and b/w wire was 0 ohms. pressing the the starter button produced a result of .9 to 1.0 ohms

running jumper from coil blue wire to negative terminal of battery and jumper from positive terminal to b/w coil wire produced an INTERMITTENT weak spark at plug 4 ONLY. number 1 plug produced no spark.

shorting the 1-4 points - everything connected as stock and yes there is spark at 1-4

please be specific regarding further tests - not that everyone hasnt been a fantastic help...but we must be certain that human error (my error lol) isnt part of the issue ...doing my best to follow along ...all tho i am not completely with out electrical experience..i will admit my own confusion..sorting thru posts and doing some of this on the fly...

the above results should be considered near gospel...

[scottly]

With all wiring connected normally, ignition switch on, measure the voltage on the blue wire at the points:
1) points open
2) points closed

[Hush]

Just a timid question here, the #1 and #4 points wire from the coil...it is on the correct side of the points pivot pole eh?
I mean I've had this same sort of problem with Honda twins where the power wire to the points on only one side was fitted incorrectly and caused me mayhem until I figured it out.
If the power wire is not fitted to the correct side of the isolator washer it's all for naught.
Probably something way more techical but my tuppence worth.

[scottly]

I mean I've had this same sort of problem with Honda twins where the power wire to the points on only one side was fitted incorrectly and caused me mayhem until I figured it out.
If the power wire is not fitted to the correct side of the isolator washer it's all for naught.

I was thinking the same thing, hence the request for voltage readings.

[TwoTired]

You can't use an ohmmeter on an energized circuit and expect to get meaningful readings.  The meter supplies (injects) it's own power and external power will alter its measurement capability.

In-circuit ohms measurement, requires the tester to control all paths of current flow.
The coils are conductive and have a common attachment to each other.  They also attach to the points.
In other words, both point contacts have a path to the other point contact.  If you are measuring contact resistance you must account for, or eliminate alternate paths of measurement flow.

Cheers,

[saw750]

blue wire at points, everything attached

points open: 10.8 volts

points closed: 1.5 volts

[saw750]

and just for fun i decided i would connect yellow from the 2-3 point to the blue from the 1-4 coil and visa versa.

i fired the starter and there was spark at 1-4 but not 2-3.

i also measured the resistance of the blue wire..disconnected at points and disconnected from coil and the result was again .5 ohms

[CB750F2]

Ok Saw. Since you get saprk at the 1-4 coil and not the 2-3 coil when you switched the bluie and yellow wires means that you have a problem with 1-4 points. This is because, with the wires switched the current for 1-4 coil is now going through the 2-3 points. In my last post I asked you to measure the contact resistance between the ground side of the points and the backing plate - you have not fed back a result. Also I suggest that you replace the 1-4 points with a known good set if you have a set available. In your last post you said that you had 11.0 volts with the points closed. Please re-do this test because the voltage across a closed set of points with should be zero or close to it. Pat