[averagejunk]

I've lurked on the forum for quite a while and learned quite a bit....but its starting to feel uncomfortably voyeuristic, so I have a question or two. Last year I resurrected a '69 ca175 and started a '65 gilera 106 last summer. I've put the gilera back together and can't get it to spark. In order to reduce the variables (coil, wiring, spark plug) involved, I tested the voltage coming off the magneto and when cranking the engine am getting only a max of 0.16 volts. I've checked all the wires in the magneto and they all have good continuity. Is there something obvious I may be missing?

 

[HackAsaw]

first step

clean the points by dragging a white piece of paper thru them until they come out clean

make sure you don't see any excessive arcing across them

and inspect for metal transfer

if you have metal transfer from one point contact to the other

note if from movable to stationary or vice versa

and come back and spill your guts if you don't know how to interpret what either means


btw....... are you measuring the output voltage with an AC meter?

you should I am pretty sure and often it's easier to do with an analog type meter instead of a digital unless you have one with a "peak hold" function

checking the ignition coil is pretty much same ol same ol

 

[averagejunk]

Yep, it was the obvious that I needed help with. It certainly made a difference once I switched the tester to AC! But still I'm only getting a maximum of 3.5 volts, shouldn't it be closer to 6? I did forget to mention that the points look new with no evidence of excessive arcing and the gap is set correctly.

You will have to explain the "same ol same ol" regarding the coil. With the ca175, I took the coil to the honda shop and had them test it. Is there an easier, cheaper to test the coil? Many thanks!

 

[jbranson]

If I'm not mistaken the Gilera 106 has two coils in the magneto, one provides 6v current to the lights and such, the other is an ignition coil which provides juice to the coil. You aren't going to get crap for voltage out of the lighting coil just kicking the engine over. The ignition coil will be very hard to read because it's switched by the points, and goes through a condensor etc.
Shame I recently deleted all my Gilera info.
JohnnyB

 

[HackAsaw]

good that they look new

did you try to clean them?

I am 99% sure you should have much higher than 6VAC on the primary side but I will have to see if I can find a book of sorts on that bike. Do you have one?

It's been many many many moons since I've laid hands on one.

if you have one and can scan it, or even post up a pic of the setup, that would be helpful

It s very easy for a digital volt meter to not display the peak voltage as it can happen faster than the LCD's can display.

You should be able to test the primary and secondary windings yourself..... both by measuring thru them and also it's output

the 6 does sound very low but you could try tying that output to a universal AC coil, I just snagged one

an emgo unit for less than 12 bucks

easy to mount

you could also snag one of most any AC or ET (energy transfer) type ignition UJM dirt bike or whatever

the coil will be marked "AC"

what kind of meter are you using and at what level do you consider your understanding of basic electronics?

 

[HackAsaw]

JB that sounds right, the 6VAC should make the lights glow

 

[HackAsaw]

one more thing........ if the magnetic rotor has been subject to impact, shock, or even stored without clamshells or it's stator in place, or ever gotten really hot

they can surely get tired and weak

even if not age definitely can cause them to lose strength

you can have them regaussed at your local airport, especially if you have access to an A&P at a smaller airstrip

and sorta telling you that just in case that 6VAC is actually the ignition primary max output and not the lighting coil

 

[jbranson]

So you'll know which is which...usually the magneto coil has fewer windings, thicker wire. The lighting coil usually has more windings, thinner wire.
JohnnyB

 

[averagejunk]

Thanks guys! I'm testing the output with a run of the mill tester that doesn't give me a peak readout, sounds like this isn't what I need. HackAsaw, I do have a book with the wiring diagram, I'll check it out when I get home. But since its a 6volt system doesn't that mean that the output of the ignition coil in the magneto should be 6 volts or does it feed a higher voltage to the coil? I get roughly the same reading (around 3VAC) from both the ignition and lighting coils when kicking it over. From what you said JohnnyB it sounds like I may not get much higher than this from the lighting coil anyway.

I tested the continuity of both coils and they look good. The points are clean.

Depending on the results of testing the output with a more appropriate tester, I have a couple of options:
1. If the output is correct I'll pick up a cheap 6volt coil
2. If the output is still low, I can try getting the magnetic rotor regaussed. HackAsaw what is "an A&P"? Do they commonly regauss rotors at airports?

As you can probably tell by now, my understanding of basic electronics is just enough to get give me a false sense of knowing what I'm doing.

Again, thanks for the help!

 

[jbranson]

I'd guess 3v is about right for the lighting coil just kicking it over. Mine wouldn't rise high enough to create any usable light from the lights unless it was turning a few thousand rpm.
I thought the magneto coil (ignition) should put out a higher voltage, which is then compressed in the condensor, dumped to the plug coil, then grounded by the points to collapse the primary windings and induce a current in the secondary windings which juice the plug.
Hehe...getting confusing since there are two "coils" in the magneto, and one coil in the ignition system.
If it's any help, I think the 160 system works exactly like the older Honda singles with no battery and seperate lighting and magneto coils.
JohnnyB

 

[HackAsaw]

airplane wrench and yes those that work on smaller craft can regauss

you'll need an AC coil

one from even a lawn mower or chainsaw repair place would work if your local cycle shop doesn't carry them or wants stupid money for what they have

not a 6VDC coil

I am thinking the ac output of the ignition coil that runs into the actual ignition coil primary should be closer to 50VAC than 6VAC

JB the condensor's function isn't to compress anything...... only to control the decaying oscillation as the field collaspes which in turn prevents the points from burning up

it's actual function can be seen on a scope as those five positive wavy lines after the spark event

I can count all the times I've ever seen a motorcycle technician test a motorcycle on an ignition o-scope and every time I've seen it..... I was the guy doing it

a condensor/cap is an AC open, and affected by frequency, and to DC is appears as a short


so sorta an easy to swallow over simplified explanation about compressing but not exactly accurate

close enough though and I'll gladly stand corrected if I've mistyped or have lost my nearly senile mind again