72 T500 no spark

Tamadrmr26 · Post by **Tamadrmr26** » Mon Feb 28, 2011 6:53 pm

i picked up a 72 t500 a couple weeks ago. im tryin to see if i can get some spark out of it. i charged up a new battery, cleaned and gapped the points, checked the engine ground and went over the wiring looking for loose connections and what not and im not getting anything. i could use some tips on what to look to now and how to test any problem areas or parts. any help is appreciated.
thanks, erik

H2RICK · Post by **H2RICK** » Tue Mar 01, 2011 12:44 pm

Erik, the first thing you want to do is pull the gas tank off (if you haven't already done so) so you can get at everything.

TAKE NORMAL PROTECTIVE PRECAUTIONS AGAINST ELECTRICAL SHOCKS WHILE PERFORMING THESE TESTS. IF YOU ARE NOT TOTALLY FAMILIAR WITH ELECTRICAL TROUBLESHOOTING YOU SHOULD TAKE YOUR BIKE TO A PROFESSIONAL MECHANIC TO HAVE THESE TESTS PERFORMED.

DO NOT LEAVE THE IGNITION KEY IN THE "ON" POSITION FOR MORE THAN ONE MINUTE WHILE PERFORMING THESE TESTS. YOU MAY DAMAGE YOUR IGNITION COILS AND OTHER COMPONENTS IF YOU LEAVE THE KEY IN THE "ON" POSITION TOO LONG.

Assuming you have a voltmeter and know how to use it, then:

AA) Get your voltmeter out and check the light gauge wires coming into the ignition coils from the key side of the wiring harness. These wires should be the red ones, IIRC. From each of the red wires to the battery ground post you should be reading battery voltage (i.e. ~12.5 volts DC) with the ignition key in the ON position.

BB) Got correct voltage on the red wires ??? Great......now check the light gauge black and white individual wires on the other post of each coil. Again, you should be reading somewhere close to battery voltage.

CC) No voltage on the red wires as per test in AA) ?? Then you've got a problem upstream somewhere with a disconnected wire, bad fuse, bad ignition switch, etc. Track down the open or short in this circuit and repair as necessary.

DD) If the voltage on the red wires is okay but you have no voltage on the black and/or white wires as per test BB) ?? Then you may have bad ignition coils.

Perform the above checks, let us know what you find and we can go from there.

titan performance · Post by **titan performance** » Tue Mar 01, 2011 3:38 pm

Have you got a spark at the points?

Tamadrmr26 · Post by **Tamadrmr26** » Wed Mar 02, 2011 5:34 am

no spark at the points, i also have full charge at the battery but the lights dont even come on so im going to go over all the wiring more carefully tonight.

rick, thanks for the help, ill post back after i try everything.

titan performance · Post by **titan performance** » Wed Mar 02, 2011 3:44 pm

OK Tamad.......so you have a charged battery but nothing works? Start by checking the fuse and the condition of the fuse holder..there's only one on the 500. If that is in order, check to battery terminals and the quality of the earth (ground). If these are all good, the first place I would look would be the block connector on the ignition switch, it's a 4 way connector about 5 inches from the switch......

Tamadrmr26 · Post by **Tamadrmr26** » Wed Mar 02, 2011 7:09 pm

ok, fuse and holder are good, terminals good, ground is good. titan, i believe the connector block you are talking about is the same thing that rick is saying to test? or are you talking about the pre key/ignition switch block?

when testing the red wires(post key, pre coil) i get good voltage when the key is one click from off, nothing when it is turned 2 clicks(clockwise from off position). is that how it should be? one click from off is the on position?

when testing the black and white wires in the same block i have the same result. full 12.4v when the key is one click from off, nothing when the key is 2 clicks from off.

to recap: AA) check
BB) check

Coyote · Post by **Coyote** » Thu Mar 03, 2011 6:24 am

One click from off IS the on position. the second click was not used in the USA. Some countries reguired running lights and that's the second position of the keyed switch. If you are trying to start the bike in the second positition, it will never happen. One click from off IS ON.

GreenMachine · Post by **GreenMachine** » Thu Mar 03, 2011 6:38 am

Coyote wrote:One click from off IS the on position. the second click was not used in the USA. Some countries reguired running lights and that's the second position of the keyed switch. If you are trying to start the bike in the second positition, it will never happen. One click from off IS ON.

I still have cramps from trying to kick-start the bike in that position. Ridiculous design.

Tamadrmr26 · Post by **Tamadrmr26** » Thu Mar 03, 2011 8:14 am

hahaha, it took me a couple mins to figure that one out.

i figured either that was the on position, or the wiring was completely whacked. im not really sure where to go from here. power to and from the coils seems to be good but no spark at the points.

Coyote · Post by **Coyote** » Thu Mar 03, 2011 8:54 am

Spark at the points is very hard to see. Have you pulled the plugs to see if they are sparking?

650hardtail · Post by **650hardtail** » Thu Mar 03, 2011 9:31 am

do you have power across the points when they are open ?

Tamadrmr26 · Post by **Tamadrmr26** » Thu Mar 03, 2011 9:58 am

no spark at the plugs either. there is power accross the points. i may have found a problem. i printed out a wiring diagram and started testing connections to and from parts. the only thing i found that wasnt getting power/ground was the r/g wire that runs from the voltage regulator, then splits, one going to the alternator and the other to the silicon rectifier(i think thats what it is) and then i believe to the ignition switch(i couldnt find it over there but thats what the diagram shows). should i have power through that wire, or does that charge come from the alternator or something?

jabcb · Post by **jabcb** » Thu Mar 03, 2011 10:43 am

The R/G wire is one of the three outputs from the alternator. It will have an AC voltage only when the motor is spinning.

Suggest you fully charge the battery. That way when you talk about voltage readings everyone will know what you are starting with.
If you provide the results somebody should have some good ideas.
The problem could have multiple causes that make it hard to diagnose, like one bad coil & one bad condenser.

Useful voltage readings relative to ground:
1) voltage for both primary sides of the coils with the points open & closed
2) voltage for the coil-side of the points when open & closed

As said by someone else, make sure you limit the time you bike is on when the engine is not running to less than a minute or so. Otherwise you could overheat the coils and damage them.

You could also check the primary & secondary coil resistances when the coils are disconnected.

Also, to protect your multimeter from damage, you should only take resistance readings when the battery is disconnected.

Coyote · Post by **Coyote** » Thu Mar 03, 2011 10:45 am

With the ignition off, put a business card between the points. With your meter set to continuity, check between the stationary point and the moving point. If you have continuity, then you are most likely shorted to ground at the pigtail. This is a common error.

Tamadrmr26 · Post by **Tamadrmr26** » Thu Mar 03, 2011 12:31 pm

with the business card in place, the point more towards to the rear of the bike gives me the beep indicating less than 30 resistance between the points. the point towards the front is giving me mixed readings. it will beep for a second, then just show the "1" for open circuit.

battery is fully charged so when i say im getting voltage i mean full 12.4v or so.

1)points open or closed i get full 12.4v
2)points open or closed i get full 12.4v

resistance through coils reads 4.5 for both coils(meter set on 200).
thats reading:
orange wire - white wire
other orange - black wire

72 T500 no spark

72 T500 no spark

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