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Discussion Starter · #1 ·
This isn't a CB but a 74 CR250 and I figure someone here would be more informative on how to solve my problem.

New Condensor, points and ignition coil. Set the points and have a good spark on the points on kickover but no spark on the spark plug.

If I remove the ground wire on the ignition coil I still get spark at the points but no spark on the points if the ground is hooked up. On kickover getting 18+ volts from the output wire on the magneto/points plate.

Any suggestions what to look for?
 

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I know my suggestions will seem a bit basic, but have you checked if the coils are powered and the engine/points plate is properly grounded?
 

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Discussion Starter · #3 ·
I have continuity from the points plate/mag to ground.

I don't understand coils are powered? When I kick it over theres 12volts to the ignition coil but as soon as I plug the ground wire into the ignition coil there's no spark on the points???
 

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When you turn the key on (and the kill switch is on) you have power to the coils usually by a black wire or black with white stripe. The negative (usually blue for one coil, yellow for the other) goes to the contact points to be grounded when the points close.

This is how it works in my CB500T and most 450s. I'm not positive on the wire colours , but shouldnt be far from it.

Edit -OH, sorry! Yours is a race bike, so it shouldnt have a battery or a key,right? Disconsider all of this.
 

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Sensei
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The coil is grounded through the core......The "ground" wire you refer to is the kill, and eliminates all spark when grounded...... I would check the plug cap as they tend to corrode internally.....
 

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Discussion Starter · #7 ·
The new ign coil came with no cap, so I used the original one. I'll pick up a new cap tomorrow and try it out. Thanks for the tip.
 

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Sensei
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You could insert a finishing nail/sewing needle and check for spark to the engine cases/head......Just DON'T hold it!....Prop it close somehow.....Make SURE the "kill' wire isn't grounded for this test (disconnect it, key on)
 

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Discussion Starter · #9 ·
66Sprint said:
You could insert a finishing nail/sewing needle and check for spark to the engine cases/head......Just DON'T hold it!....Prop it close somehow.....Make SURE the "kill' wire isn't grounded for this test (disconnect it, key on)
Tried the needle in the spark plug wire on 3 different ign coils and still nothing!! There's no ground wire from the engine to the frame, although the engine is bolted to the frame with no rubber mounts?
 

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Sensei
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Follow that single magneto wire (that goes to the coil and "kill") back to the mag....It MUST be shorted to ground or broken somewhere....
 

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Discussion Starter · #11 ·
66Sprint said:
Follow that single magneto wire (that goes to the coil and "kill") back to the mag....It MUST be shorted to ground or broken somewhere....

Replaced the wire from the magneto to the ign coil. Continuity is good. With a good strong kick get -18+ volts.

This has me confused I'm getting minus voltage from the mag (meter probe red-pos on the mag wire and neg probe on engine ground).
 

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Sensei
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NO... It's a magneto......(which is a FORM/TYPE/Variant alternator)
Your output goes through a single wire to the ignition coil... the "other" connection IS through the chassis....IF the single wire is "grounded' to the chassis anywhere, it effectively 'shorts the output" and acts as a "Kill".... The coil's metal core is the "other' electrical connection..... IT must make good frame contact, as must the engine....
 

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Discussion Starter · #15 ·
I'm running a jumper wire from the single output wire on the magneto directly to the power side of the ign coil. It's a new plastic type ign coil that screws to the frame, there's no metal to metal contact from the coil to the frame.

The ign coil ground wire is removed (kill switch wire). With this hookup still no spark, but if I remove this direct wire to the ign coil the points will spark??
 

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Sensei
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ANY electrical circuit REQUIRES both legs (wires) be connected .... output AND return.... does the coil have only one wire terminal? (ground could be internal to the mount and concealed).....
 
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