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GenuineThumpy

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Hi guys

New to the forum, have a problem with my genuine thumpstar engine, i recently replaced the stock magneto with one of those performance magnetos off ebay,
but i cannot for the life of me get spark.
ive replaced the coil, spark plug, and try every possible combination of wiring here is, but still no spark,
the engine is a 125cc Genuine.
anyone got any ideas of what it could be?
let me know if you need any more info
thanks
 

motodevo

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If its a inner rotor kit(unless its a good Japanese one like a kitaco, etc.) throw it as far away from your bike as possible, they are absolute junk
 

my67xr

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was it either one of these ?
the 1st type pictured are known to be a bit unreliable, unless it's a decent brand.
the 2nd type pictured is a way better stator



 

GenuineThumpy

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It is the one in the first one, I know they can be a bit unreliable an i hear the CDI's fry themselves fairly easy, but Icout one in my old bike years ago and had no problems with it, couldn't remember how I ha the wiring, but I've Reyes the way the instructions that come with it ( even though they are absolutely ridiculous) I've gone off 3 other diagrams, and the way it would make most sense to have the wiring. But nothing, I spouse it's quite possible that I got sold a dud, but I don't know, another thing I'm thinking it could be is the spacing between the positive magnet thing,
You have the 2 magnets on the left, which have a 1mm gap between the flywheel. But then on the right where I think it is the positive magnet thing, has about a 4-5mm gap between it and the flywheel, not sure if that is how it is supposed to go, but I can't adjust it, I can adjust it to move around the flywheel, but not move in closer to the flywheel, that's the only other thing that I can see it would be
 

my67xr

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have you tried wiring it up like it is in the picture above?

the bigger coil is the charge coil, this sends the power to the CDI to be amplified, and when it gets triggered it will send the amplified power over to the ignition coil.
the small coil is the crank angle sensor/trigger, it tells the CDI when to send the power to the ignition coil.

have you tried running an earth lead from a bolt on the motor, over to where the 4x earth wires connect to the bare metal on the frame?
 

my67xr

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have you tried starting it with the kill switch disconnected?



the 5mm gap from the crank angle sensor to the tab on the flywheel does sound a bit excessive.
the standard flywheel type ignitions like in the second picture, run a .1" gap to the pickup sensor.

just thinking,
do the 2 screws that hold the sensor down come out away form the sensor?
if so try removing 1 screw totally, and loosen the other a little.
then move the end without the screw over closer to the pickup point on the flywheel, so it is very close but wont touch if you kick it over.
then tighten up the one bolt holding the sensor to the backing plate.

next kick the bike over with the kill switch in the run position and spark plug removed from the head and let the threads earth onto the fins of the motor.
see if you get a spark then?



post up your results
 

GenuineThumpy

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Yeah the one in the picture is the way I wired it up first cause I thought that made the most sense, and no I haven't tried running another earth from the engine to the exciting ground wires, will give that ago tomorrow
 

GenuineThumpy

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An yes I've tried it with the kill switch disconnected and tried it when the kill switch was set to off, cause I know sometimes they can go backwards, I've tried bolting that main earth wire to the engine which didn't work then I tried running it with the other earth wires since the coil is grounded so I assume they all should be earthed
 

GenuineThumpy

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tried running an earth wire from a bolt on the engine to the 4x earths to the frame and no go,

here is how i have it now(the way most diagrams told me to have it and the way the bike mechanic at the thumpster shop told me to have it) and i managed to move the crank sensor over a little more to the flywheel, not sure if it not close enough still, but heres a pic of that too



 

my67xr

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do you have a multimeter handy ?
if so, can you set it to 200 Ohms, it will read 1, (meaning no connection/circuit)
put one lead to the white wire, and the other lead to a green
what reading do you get on the meter ?

now set the meter to 2000 Ohms,
put one lead to the black coming from the stator, and the other to a green
what reading do you get from there ?
 

my67xr

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hmm, you should get a reading off both.
can you unplug the black and white from the stator and try the test again?


also can you remember which wires had a horseshoe terminal on the ends of the wires?
and which green had a ring terminal?
 

my67xr

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if you still dont get a reading,
try one lead from the meter to one of the coil mounting screws on the stator to get a good earth, (instead of going to a green)
 

GenuineThumpy

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i just checked again. when i try to put the multimeter to the wires on 200ohms and 2000ohms, they screen just fades out and goes blank, but when i put it on 20k ohms it reads 50. something, and the green wire with the ring terminal is bolted tho the engine as you can see in the pi and im not quite sure what a horseshoe terminal is
 

GenuineThumpy

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just put one of them directly onto the coil mounting screw and got the same thing, all of the voltage meters work fine, but its just 200 and 2000 ohms the screen fades out when i put it on the wires, is that something dodgy with my muti meter or?
 

my67xr

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i have another idea for you to try,
undo the 2x stator to engine case screws, and carefully turn the stator plate around so the small coil is at the front and the bigger coil to the rear
then refit the 2x screws and try kicking it over

the gap on the pickup coil is still too big imo.
does rotating the backing plate change that gap at all ?
 

GenuineThumpy

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Sorry yeah my Miri meter was stuffing up, I finally got an accurate reading I think
The black wire is saying 3.94 and the white .58
 

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