How do I test my CDI box?

Greg58

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May 1, 2011
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Take the sparkplug out of the head and connect it to the plug wire, lay the plug on the head so you can see the end, roll the bike with the clutch out. As the engine turns over you should see a spark, if not try a second plug.
 

Bikeguy Joe

Godfather of Motorized Bicycles
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Look at the picture you posted....where is the plug lead going to?

Be sure you are getting fuel to the cylinder. Is the plug wet? It could be low/no fuel flow, a leak somewhere in the intake, or even a blown head gasket.
 

Chrisbull420

New Member
Apr 20, 2020
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Look at the picture you posted....where is the plug lead going to?

Be sure you are getting fuel to the cylinder. Is the plug wet? It could be low/no fuel flow, a leak somewhere in the intake, or even a blown head gasket.
I took the boot off the plug to do a chop.
 

Greg58

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You said earlier the sparkplug was firing so I would look elsewhere, do you have good fuel flow? Try to start it as normal, then pull the plug and see if it's wet. Pull the carb and clean it out good.
 
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Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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I concur with Greg58... If you see a spark?, you should look elsewhere for the problem.
If the plug is wet?, the spark will travel through the liquid on the plug instead of jumping the air gap.
& as he also said, the next thing you should check is if the jet is clogged in the carb
 
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