Random sparking from spark plug

[SdCruizer]

just be glad all these parts are cheap

im coming from large street legal scooters to these bikes and these parts are dirt cheap compared to scooters
too bad on the quality though its the weakest link

 

[toojung2die]

Hey Kev... Glad you got back to us. Could be the CDI, could be the magneto, could be as simple as a bad ground. Same symptoms, weak diagnostics for these motors. I have a good working CDI and the measurements I get from it are not even close to the values another member posted way back. I used a Fluke digital and a Triplet analog to measure. Whatever is going into those epoxy embedded circuits has yet to be definitely determined. I won't go for a long ride without a spark plug, CDI and magneto coil in the kit bag. We'll all benefit when you find the fix.

 

[Big Red]

Random Spark

Yeah Kevin, Sorry we got side tracked on you.
Even though you didn't have the white wire hooked up I still think it's your coil. If a CDI goes bad you wont get any spark. If a coil is bad your gonna get a spark once in a while, not enough to run it. And I've never seen a magneto go bad. It's just a big magnet. Unless it somehow looses it's magnetism or just gets weak? I'm not saying it can't happen, just saying I've never seen it.
If I had an extra coil I'd just send it to ya. I've had a couple go out lately too so I'm all out of em.
Another possibility is that the coil simply has a bad ground wire. Sgt. Howard came up with a solution for this. It seems the china guys do a cold solder on the ground wire and it don't hold up to heat and vibration very well.
http://www.motoredbikes.com/showthread.php?t=36233&highlight=coil+ground
If the coil aint totally fried then this might work for you. It worked for me.
Big Red.

 

[toojung2die]

If a CDI goes bad you wont get any spark.

Big, I can tell you from my very first experience with a HT that a bad CDI can cause a weak and intermittent spark. I still have the bad CDI in a zip-loc bag and I'll send it to you if you have any doubts. (hopeless packrat I am)
I thought at first I had a bad magneto coil so bought a new one and a CDI just in case. Bad CDI.

My whole career has been diagnosing and repairing. It's what I do. Never discount anything as the possible cause of a failure. Even if you think it's totally stupid. It's still possible. "No, it couldn't possibly be that", has burned my butt once too many times and taught me some humility.

 

[kevingkruse]

@Big Red
I actually did what Sgt. Howard said in that post, no fix. I'm just gona order both the CDI and coil, can't hurt havin both.

 

[Big Red]

Big, I can tell you from my very first experience with a HT that a bad CDI can cause a weak and intermittent spark. I still have the bad CDI in a zip-loc bag and I'll send it to you if you have any doubts. (hopeless packrat I am)
I thought at first I had a bad magneto coil so bought a new one and a CDI just in case. Bad CDI.

My whole career has been diagnosing and repairing. It's what I do. Never discount anything as the possible cause of a failure. Even if you think it's totally stupid. It's still possible. "No, it couldn't possibly be that", has burned my butt once too many times and taught me some humility.

Yer right, NEVER say never. A CDI is an electrical component and 99.999% of the time if it's out, it's all the way out. I guess it COULD just go weak. A coil & mag on the other hand is a field generator and will get weak, loose the proper ground or just burn. MOST of the time (99.999%) when your getting an intermittent spark look at the coil first. But if you REALLY want to make sure, replace the CDI, the coil, and upgrade the plug and wire if you haven't already.
I don't know why, But I've got a couple bad CDI's in my junk box too. They are right beside the bad coil's.
Big Red.

 

[HeadSmess]

Whatever is going into those epoxy embedded circuits has yet to be definitely determined..

they have bben pulled apart and reverse engineered, you can make one for about$5...

a capacitor, a resistor, a diode or two and a silicon control rectifier.

search on other sites. people seem to post schematics there, not here.

 

[toojung2die]

they have bben pulled apart and reverse engineered, you can make one for about$5...
a capacitor, a resistor, a diode or two and a silicon control rectifier.
search on other sites. people seem to post schematics there, not here.

Well that's cool. I was following a thread on another MB site about this a while back. They were still trying to figure out how to remove the epoxy without damaging the embedded components. $5 for a homemade CDI sounds about right since you can buy a Chinese replacement for around $15. Care to share your schematic here? You could begin a trend or even warrant a Sticky.

 

[HeadSmess]

http://motorbicycling.com/showthread.php?t=28439&page=17

seemed to have it sussed i think....

what annoys me is how my spark has decided the 15mm gap through the boot to the frame is far more appealing than the .5mm gap on the plug...

a day left! just a day! and i get my license back....grrrr!

 

[kevingkruse]

fixed!!

Yay! I replaced my magneto coil and my bike works fabulously again. So I'm guessing that when I would repeatedly tap my killswitch to make it bikefire, which I'm not going to do anymore, it fried my coil? Well whatever it was, it works now, I love my bike... and sorry about takin forever to replace it, took me longer than I thought to save up a whopping 14 bucks, lol.