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Motorized Bicycle Trouble Shooting Use this area to post problems that may arise, if you could use some help in figuring out what is wrong with your engine and what needs to be done to achieve top performance.


Delayed CDI failure?

Use this area to post problems that may arise, if you could use some help in figuring out what is wrong with your engine and what needs to be done to achieve top performance.


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  #1  
Old 05-18-2013, 10:29 AM
Fun Key Bay Bee Fun Key Bay Bee is offline
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Unhappy Delayed CDI failure, or carb issue?

Hello! I'm new 'round these forums, and to gas cycles, so this is also my introduction. I'm from Portland, OR, and have just built my first motorized bike. I hope to be good addition to the community here!

I've hit some snags during the build, but now I have a problem which I think needs a second opinion before I shell out more $$$.

I had the bike running fine, perfectly functional at all throttle levels. Then my engine began to sputter, and while running the engine, I noticed I only heard the sound of combustion half of the time, more so if I encouraged it with pedaling. Then it stopped. Gah!

I checked the wires running from the magneto to the cdi, aaaand I forgot to tape them down. Doh! Totally melted them against my exhaust, fusing the two black and blue wires together, shorting it out. I fixed the wires (wire was fully intact, but insulation was gone in a 1/2 inch area of the wire, so I taped the non-insulated parts and also taped the two wires away from each other just to make sure they were no longer capable of shorting.)

Fired right up! Phwew! Rode the bike for 2-3 miles then returned home. However, right when I pulled into my house, I could feel the engine dying. I tried to fire it up again, but now it doesn't even combust at all! I checked the plug for spark and it is firing, but possibly not strong enough for combustion. The wires are still fully intact too.

I read a post on here about another guy who had the exact same symptoms/possible cause as me (sputtering out and failure, caused by incorrect wiring), and a cdi replacement fixed his problem. However in my case, I had my CDI working AFTER I fixed my wires, and THEN it stopped working after a couple miles. Is it still possible that the CDI is the issue, and there was just a delay in the onset of symptoms?

Thanks in advanced for any input, and I'll see you around the forums!

-Jake

EDIT: Thanks for the replies so far.

Unfortunately, after taking the plunge and buying the CDI, it apparently wasn't the last of the problems. I'm getting strong spark, but still no ignition. Guess that means I'm not getting gas? The fuel petcock/filter assembly is good, so it must be the carb. The float isn't stuck. After a few tries to start it, I took off the carb and the neither the carb's jet or engine intake was wet with fuel. Any ideas as to what could be wrong?

Last edited by Fun Key Bay Bee; 05-23-2013 at 09:33 PM. Reason: Change in problem details
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Old 05-18-2013, 11:16 AM
crassius crassius is offline
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Default Re: Delayed CDI failure?

I'd first try a new spark plug, as sometimes they will get fouled such that they will spark outside the engine, but under compression the spark will leak up the electrode instead of jumping the gap.
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Old 05-18-2013, 11:25 AM
Fun Key Bay Bee Fun Key Bay Bee is offline
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Default Re: Delayed CDI failure?

Ohp, sorry forgot to mention, I tried a new spark plug first, got a shiny new NGK-B6HS. I gots spark but no ignition. :/

I should also probably mention that this is a recent development. I've already rode somewhere around 18 miles on it, then I began having troubles around the time I discovered the melted wiring.

Last edited by Fun Key Bay Bee; 05-18-2013 at 11:31 AM.
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Old 05-18-2013, 01:39 PM
crassius crassius is offline
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Default Re: Delayed CDI failure?

I've seen many CDI units that fired at the wrong time & had to be replaced - not sure if your wiring problem could have heated an internal component such that timing is now off, but trying a new CDI would be my next step.
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Old 05-23-2013, 09:25 PM
Fun Key Bay Bee Fun Key Bay Bee is offline
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Default Re: Delayed CDI failure?

Thanks for the replies so far.

Unfortunately, after taking the plunge and buying the CDI, it apparently wasn't the last of the problems. I'm getting strong spark, but still no ignition. Guess that means I'm not getting gas? The fuel petcock/filter assembly is good, so it must be the carb. The float isn't stuck. After a few tries to start it, I took off the carb and the neither the carb's jet or engine intake was wet with fuel. Any ideas as to what could be wrong?

Thanks again in advance

Last edited by Fun Key Bay Bee; 05-23-2013 at 09:33 PM.
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Old 05-23-2013, 10:03 PM
Drewd Drewd is offline
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Default Re: Delayed CDI failure?

There is an inline filter screen in the petcock assembly. Remove it and install a real inline fuel filter and you shoudl be good to go.
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Old 05-23-2013, 10:53 PM
Fun Key Bay Bee Fun Key Bay Bee is offline
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Default Re: Delayed CDI failure?

Problem solved!

I think the CDI was half the issue, cause it fires much stronger now.

The other half, I'm too embarrassed to admit. But it may or may not have everything to do with being out of fuel....

Thanks for your help!
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Old 05-24-2013, 08:29 PM
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maniac57 maniac57 is offline
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Default Re: Delayed CDI failure?

Save the used cdi. It may not have been bad...
Don't feel too bad, most people who ride gas powered stuff either run out or forget to turn it on at least once.
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Old 05-24-2013, 09:28 PM
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Toadmund Toadmund is offline
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Default Re: Delayed CDI failure?

Quote:
Originally Posted by Fun Key Bay Bee View Post
The other half, I'm too embarrassed to admit. But it may or may not have everything to do with being out of fuel....
Yes, that would be problematic.
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