Blowing fuses, traced to electronic ignition

[connor1]

Working on a 1972 650 XS2 with the points replaced with a circuit board. I used the attached diagram to wire the electronics, as I put this rebuilt engine into a different frame. For the past two days I have not been able to get the plugs to produce any spark. Coils are new dual output, and all wires and electronic are new.

Started blowing fuses on the circuit I can to the coil, this circuit also supplies power to the electronic ignition. I uplugged all the connections on the circuit, replaced the fuse, and switched the power on, and the fuse remained intact. I then hooked up the coils, still no blown fuse. Then I went to connect the small red wire from the electronic ignition and it arced before I even touched the ends together, and pop went the fuse

I removed the inspection cover, and inspected the wires (red, green and black), no obvious faults.

My guess is that the electronic ignition has a direct short. For some reason it seems to be allowing current directly to ground....Does this sound likely? Is the fixed buy a new electronic ignition? Anything else to check?

 

[jd750ace]

Does not sound likely, so why don't you use a meter to check for continuity from the red wire to the electronic ignition? And BTW, for God's sake DISCONNECT THE BATTERY when wiring! Good way to burn your bike down. Have a look at my custom fried primary lead below.

 

[connor1]

Does not sound likely, so why don't you use a meter to check for continuity from the red wire to the electronic ignition? And BTW, for God's sake DISCONNECT THE BATTERY when wiring! Good way to burn your bike down. Have a look at my custom fried primary lead below.

I had the switch on to see where the short was. The arc pretty much gave it away. To check continuity I will run my voltmeter from the red wire at my NAPA fuse box to the soldered connection for the red wire under the inspection cover where the points used to be, correct?

 

[connor1]

There is continuity between the where the red wire starts at the fuse box to the soldered red wire on the circuit board under the inspection cover. I also touched the ground contact at the circuit board and it too has continuity to the red power wire.... Why would that circuit be closed? Isn't this a short with no resistor? This would explain the blown fuses wouldn't it?

 

[jd750ace]

Check from the red wire at the fuse to ground as well. then disconnect the Pamco and check the wire itself to ground, and the black wire to ground on the Pamco. With the Pamco disconnected, check for continuity between the red and black on the circuit board.

 

[connor1]

With the red power wire connected to the Pamco smaller red wire there is continuity to ground (cyclinder).

With the red power wire disconnected from the pamco, no continuity between the power wire and ground.

There is continuity at the circuit board between the red and black soldered terminals and also between the red terminal and ground and the black terminal and ground.

 

[pamcopete]

connoe1,

That is an earlier PAMCO with a protective diode shown in your picture in the upper right hand corner. The diode is there to protect the Hall sensor from voltage spikes, but if there is a continuous high voltage, then eventually the diode fries. However, being as it is a diode, it will show a short with the meter probes in a certain direction, so try it in both directions.

The unit will work without the diode so you could try just clipping it out of the circuit if you have done testing to determine that the PAMCO red wire is the source of your short to ground and the diode shows a short in both directions.

If you are out of warranty, we now offer to sell the plate only for $63.95 on the web site
www.yamahaxs650.com so you can reuse the rotor and not have to buy a complete system.

In any event, be sure to check your battery voltage as soon as you get the engine running again as I suspect you may have a high voltage condition.

 

[connor1]

connoe1,

That is an earlier PAMCO with a protective diode shown in your picture in the upper right hand corner. The diode is there to protect the Hall sensor from voltage spikes, but if there is a continuous high voltage, then eventually the diode fries. However, being as it is a diode, it will show a short with the meter probes in a certain direction, so try it in both directions.

The unit will work without the diode so you could try just clipping it out of the circuit if you have done testing to determine that the PAMCO red wire is the source of your short to ground and the diode shows a short in both directions.

If you are out of warranty, we now offer to sell the plate only for $63.95 on the web site
www.yamahaxs650.com so you can reuse the rotor and not have to buy a complete system.

In any event, be sure to check your battery voltage as soon as you get the engine running again as I suspect you may have a high voltage condition.

The diode is the blue cyclinder shaped item with the stripes, correct?

How do I check a "short in both directions" as you suggest me to do above before I clip off the diode?

BTW, I am beating my head against this bike in South Charlotte, NC, not too far from you, Pamcopete.

Thanks to BOTH of you for the help!

I am making slow progress on this bike only because when I get stuck, someone on this board has the answer and the patience to help out a newbie!

 

[connor1]

I just tested the top soldered terminal and the bottom soldered terminal of what I think is the diode for continuity to ground. The top does not have continuity to ground but the bottom does.

Does this mean the diode is ok?

 

[pamcopete]

The diode is the blue cyclinder shaped item with the stripes, correct?

How do I check a "short in both directions" as you suggest me to do above before I clip off the diode?

BTW, I am beating my head against this bike in South Charlotte, NC, not too far from you, Pamcopete.

Thanks to BOTH of you for the help!

I am making slow progress on this bike only because when I get stuck, someone on this board has the answer and the patience to help out a newbie!

Just reverse the red and black test leads to test in both directions. You should have said something earlier about South Charlotte and the cold beer... Is that Pineville?

 

[connor1]

Just reverse the red and black test leads to test in both directions. You should have said something earlier about South Charlotte and the cold beer... Is that Pineville?

How many cases and what flavor do you prefer? I can be at Harris Teeter in 5 minutes!!


Just south of 485 on Rea Rd, near Stonecrest.

 

[connor1]

Just tested the blue cyclinder (diode?) in both directions.

The top terminal does not have continuity to ground in either direction.

The bottom has continuity to ground in both directions.

 

[pamcopete]

Connor1,

Should be just the opposite because the top terminal is ground. Try again and use a higher scale.

 

[connor1]

Wait,

Is the diode the blue cylinder or the black one?

I just tested the black plastic cylinder for the first time and it has continuity to ground to both soldered terminals in every configuration of the leads.....maybe this is the diode?

Is the blue cylinder with the stripes a resistor?

 

[connor1]

So I used my diode tester function for the first time a few minutes ago as per the instruction manual.

Set to the diode test setting, without the leads touching anything the display read OL (overrange).

With the leads on the ends of the suspected diode (black cylinder) the display read "0" in both directions.

My voltmeter automatically selects range, I cannot select one.

 

[pamcopete]

Connor1,

Yes, that's the diode and it looks like it may be shorted so just cut it out of the circuit. The diode is a black cylinder with a single grey stripe.

 

[connor1]

Just had the wife hold a plug against the cylinder to check spark as it kicked it. Bike started up halfway through the kick one one cylinder. Nice bright blue spark.

Thanks for your help guys would have never found that fault without you.

Questions-

1) Without the diode, am I reducing the reliability?

2) Should I just order that new plate?

3) Why would the bad diode cause a direct short?

Thanks again!

 

[pamcopete]

Well, the real intent of removing the diode was to confirm where the short was coming from. You should replace the plate. The diode is connected directly between the red wire and ground, so when it shorted out it blew the fuse.

While you have it running with the diode removed it would be a good time to verify your battery voltage. You can keep the plate without the diode as a spare.

 

[connor1]

Well, the real intent of removing the diode was to confirm where the short was coming from. You should replace the plate. The diode is connected directly between the red wire and ground, so when it shorted out it blew the fuse.

While you have it running with the diode removed it would be a good time to verify your battery voltage. You can keep the plate without the diode as a spare.

New plate ordered!