No Spark TroyBilt TB 575EC

[TonyCooper]

No spark. Removed clutch, cleaned magneto, set gap with business card, checked magnetism, inspected wires. Resistance between plug wire and ground is 2.5 K ohms. Resistance between plug wire and red wire connector on coil (to cut of switch) is 4.5 M Ohm. Plug is good.

What am I missing?

 

[BlazNT]

You are missing that the magneto could be bad. First, remove kill wire. Check for spark.

 

[TonyCooper]

You are missing that the magneto could be bad. First, remove kill wire. Check for spark.

Thanks. I did remove the kill wire (red wire going to tab on magneto to the kill switch) and still had same results. I too think the magneto may be bad but it may be shorting out when it is active since it seems the resistance is good in a static mode (secondary 2.5 K ohms to ground and almost 5 M ohms between primary and secondary). I removed the plug and connected it via the plug wire and then ran a ground wire from plug to engine ground. Turned out the lights and turned the engine over with a drill and no sign of spark.

Have you seen a bag magneto that seems to be good with a resistance check?

Appreciate your response.

 

[BlazNT]

Have you flipped it over and tried it? They can be put on upside down.

 

[bertsmobile1]

:welcome:

you can not test a modern magneto with an Ohm meter and some cheaper ones will destroy it.
There is a hall effect trigger chip potted inside the coil which is easily damaged and prevents resistance readings having any meaning,
Secondary resistance ( plug to coil ) is worth while doing only if checking for an open circuit in the plug cap, which is fairly rare.

Pull the kill wire off the magneto and spin the engine
no spark = dead magneto ( always the chip ), not repairable.

 

[TonyCooper]

:welcome:

you can not test a modern magneto with an Ohm meter and some cheaper ones will destroy it.
There is a hall effect trigger chip potted inside the coil which is easily damaged and prevents resistance readings having any meaning,
Secondary resistance ( plug to coil ) is worth while doing only if checking for an open circuit in the plug cap, which is fairly rare.

Pull the kill wire off the magneto and spin the engine
no spark = dead magneto ( always the chip ), not repairable.

You have provided insight that I was not aware of. I did not know about the chip. It had seemed obvious that for some reason the mag was bad but I could not understand the "why" of it all. Thanks again for the info you provided. I will now start shopping for a mag to see if this thing is worth repairing.

 

[bertsmobile1]

You have provided insight that I was not aware of. I did not know about the chip. It had seemed obvious that for some reason the mag was bad but I could not understand the "why" of it all. Thanks again for the info you provided. I will now start shopping for a mag to see if this thing is worth repairing.

Magnetos are fairly cheap .
After market ones from Prime Line, Stens, Rotary will be fine.
Unbranded one on the web ( even from Amazon ) are best avoided.

 

[TonyCooper]

Magnetos are fairly cheap .
After market ones from Prime Line, Stens, Rotary will be fine.
Unbranded one on the web ( even from Amazon ) are best avoided.

Thanks for the info - will check them out.