bad cdi i think? need real world ways to test

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matthurd

New Member
Dec 13, 2010
817
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manchester NH
so i'm pretty new at these things although iv'e read tons of stuff here, anyways my bike wont run at all anymore, i put it aside after its maiden voyage because of chain rub on the frame, got most of it taken care of today, went to try it (although thanks to a tight spot a single link would rub my frame the rest was fine though) anyways the motor wouldn't start and me and a few other people started looking for the problem and determined we didn't have spark, (also found out i'm apparently running to much fuel/not enough air into it since my plug was black and oily)

we did this by taking the plug out and rolling the bike at which point from what we understand there SHOULD be spark, but there wasn't.

we metered it but the posts i found were somewhat hard to understand so we're not sure how accurately we did it.


i'm not sure how these things work exactly so is there any other simple/fool proof tests to see what the problem is? and from there we can figure out what else may be wrong?

the only other change i made while we had it put aside was lossening the flower nut 2 notches to make pulling the clutch easier, iv'e since moved the nut back 2 notches to its original position to rule it out as a possible thing i goofed on.

thanks.
 
Goat Herder

Goat Herder

Gutter Rider
Apr 28, 2008
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This is going to sound silly forgive me? But were you grounding the plug against the motor when checking for spark?
 
Hot Wheels

Hot Wheels

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Jul 7, 2009
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chicago
I don't know a good way to check your cdi, if you got another one change it. One thing I do know is DO NOT ground it to your frame, the black wire coming out of the motor is grounded if you ground your cdi to the frame it can short it out. I hope your running soon. brnot
 
Mac

Mac

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Dec 3, 2009
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Try this:

Use Low Ohm-Meter Scale About 200 Ohms

1) Check Ohms between BLACK wire and WHITE wire. Reading should be around 2 Ohms
2) Check ohms between BLUE wire and WHITE wire. Should be around 300-400 ohms.

CDI

Use Ohm Meter High Scale About 200-K
1) Positive lead on BLUE wire and Negative lead on BLACK wire should read infinite (no activity)
2) Positive lead on BLACK wire and Negative lead on BLUE wire. Should be about 130-150 K-ohms
3) Positive lead on Spark Plug wire and negative lead on BLUE wire. Should read between 135-155 K-ohms

Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms

Hope this helps. I got this info compliments of 2door.

Mac
 
Goat Herder

Goat Herder

Gutter Rider
Apr 28, 2008
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matthurd said:
nope, made sure to keep the kill switch wires away from anything.
Click to expand...
The plug itself the metal portion the threads that attach it to the cylinder head have to be physically grounded to the motor casing when checking for spark. This must be done to complete the electrical circuit. If you fail to do this you will never see any spark when cranking the motor over.
 
M

matthurd

New Member
Dec 13, 2010
817
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manchester NH
i'm sorry i misread your other post, i thought you were talking about the kill switch wires grounding it out, getting late here lol. i did have the plug set on the top of the motor trying to do that, i'm assuming i was successful in that part although i'll retest it tomorrow to make sure.
 
darkhawk22

darkhawk22

New Member
Aug 17, 2010
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Acworth, GA
I had a bad CDI once. I tried everything, even a new Carb before I just switched out the CDI and the bike cranked first try. The crazy thing was that I had spark to the frame when I removed the old CDI but not enough to crank the engine and keep it running. I also have a spare magneto just in case now. Here's a link to a performance CDI but I have not seen any reviews on it:

Limiter CDI and HP Ignition Coil
 
LS614

LS614

Active Member
Dec 22, 2009
1,236
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matthurd, the tools that you need for testing are a voltmeter, a screwdriver, and a spark plug tester. If you are absolutely sure you don't have spark, then disconnect your CDI and put a voltmeter on the output wires of your magneto to see what kind of volts and watts you are getting. It should be ~6 volts and 3watts when revving. If you are not getting voltage, either your magneto coil is dead, or your magnet has lost its magnetism. Good luck :)
-LS
p.s. http://www.harborfreight.com/90-inline-ignition-spark-checker-4445.html here is the spark checker tool
 
M

matthurd

New Member
Dec 13, 2010
817
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0
manchester NH
wish you had posted this a week ago lol. think my magnetos fried cause i replaced the cdi after asking other members and them saying cdis die more often, didn't fix it.
 
M

matthurd

New Member
Dec 13, 2010
817
2
0
manchester NH
i'll be going with pirate again for the magneto,it's closer to me by about 3,000 miles and the sweet tarts he includes can help me cope with my sudden depression of not being able to ride :(

not gonna lie though the mounts on the cdis prate sells are garbage, it's actually tearing off the side, and i didn't tie it down nearly as tight as the one that came with my grubee kit.

it seems a bit beefier and the connection is much more solid though, just gotta make sure it doesn't tear anymore or it will fall off on me :(
 
Dirt Road Cowboy

Dirt Road Cowboy

Member
Sep 18, 2011
296
0
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Tyler Texas
Mac said:
Try this:

Use Low Ohm-Meter Scale About 200 Ohms

1) Check Ohms between BLACK wire and WHITE wire. Reading should be around 2 Ohms
2) Check ohms between BLUE wire and WHITE wire. Should be around 300-400 ohms.

CDI

Use Ohm Meter High Scale About 200-K
1) Positive lead on BLUE wire and Negative lead on BLACK wire should read infinite (no activity)
2) Positive lead on BLACK wire and Negative lead on BLUE wire. Should be about 130-150 K-ohms
3) Positive lead on Spark Plug wire and negative lead on BLUE wire. Should read between 135-155 K-ohms

Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms

Hope this helps. I got this info compliments of 2door.

Mac
Click to expand...
I just tested my CDI after I couldn't even get a pop with starting fluid.

I was getting between 600 - 700 K-ohms between the blue and black wires, no matter which way I connected the leads.

I also got nothing between the spark plug and blue wire.

Looks like I may have to roll my own.

Thanks for the info!
 
Cyclin

Cyclin

New Member
Jul 4, 2011
118
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California
I dunno man I have never had a CDI go out on me. I had thought it did before and bought a replacement but it turns out the CDI was fine all along. I have had 2 killswitches short out so make sure that is not hooked up when you are testing. As LS614 said if you are not getting voltage then it is your magneto. That part has gone out on me before. If it does turn out to be the magneto, when you replace it make sure to seal up the mag housing before you take her out again. A new gasket and some permatex or the permatex by itself should work. I usually use Permatex Blue Gasket Maker. If moisture gets into the mag housing it can kill your mag pretty quickly. Mine actually happened not while it was raining but just due to morning dew on a more wet morning than usual and being left outside that night.
 
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