Ignition failure

turnofftheradio

turnofftheradio

Member
I left my multimeter at work so I can't do any tests till I get home later. Anyone care to take guesses at what failed? I'll post what I found to be the problem, I should have a replacement for every component.

I use my white wire, I have an ngk plug, I was using the stock wire and boot still. 175 miles ago had a bearing fail that beat up my mag and rotor, but they have not been a problem yet, so I kept using them.

Here's what happened. 15 miles wot (30-35mph)nearly the whole time, 10 min break, 15 mile return trip, providing the same throttle. About a mile from home after a red light and a turn, she gave an erratic poppy mess of firing, during the turn she totally gave up. plug has great color. ground for magneto still soldered on. pedal home in shame uphill. The good news is that a sheriff tested my moped legality and let me go without incident in the first mile.
 
I've seen coils come loose from the armature after getting smacked due to a bad bearing - this can short it internally.
 
crassius said:
I've seen coils come loose from the armature after getting smacked due to a bad bearing - this can short it internally.
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truth is, I was surprised it worked at all after the beating, it was really ground on the downstroke side. But, its been problem free until this incident. I only have one spare (used) white wire magneto in my box. I'm only guessing cdi because it "felt" like it to me, there is no evidence I am right. I have one very old one from a 49cc in my box that hopefully is good. I'm counting the hr. left before vacation right now...
 
I have never seen a CDI box fail yet in almost ten years of playing with the HT motors.
Dozens of coils, but no CDI's.
Just my experience.
 
IMAG0854_zps8c38cacd.jpg

Well, today isn't the day for a cdi failure either. bad coil. Off and running again.
 
Glad to see you're running again, I usually tend to suspect the mag coil when the ignition fails but stays working and tends to cut out before completely failing. had it happen before, but I've also got a brand new engine with a bad one before as well...
 
Knock on wood I have had no problems with the mag coils or CDI units, only CDI failure I ever had was a unit that was made by a member here, it only lasted about 25-30 miles before it went out as if it had been hit by "Lightening"....

Never had a minutes trouble so far with the stock units and I have found that as far as overall performance and top speed, the stock units deliver exactly what these engines need, I have a couple custom built CDI's one running on a bike now and another one (The Rocket CDI) that I plan to set up in place of the one in use now for a comparison to see if the Rocket CDI gives the same performance on my engine as the Lightening CDI, if so its a much less expensive choice and is sold by a member here that also gives a good warranty on them, neither will out perform a stock unit on my engines, or at least I don't think they will, I like having the hotter ignition coil which may make ignition a bit better with higher compression engines but, it's more of a novelty to me and from my personal experience I honestly think it is basically just a novelty item that really doesn't add any noticeable amount of performance gains.

I know there are people who are making the ignitions for the fun, recognition and the extra pocket change involved, I have no problem with that at all, it's no different than putting chrome valve covers on an old small block chevy to dress it up, no gains but its a novelty and looks kewl.

we can buy 5-8 new stock CDI units for the cost of one custom built one that doesn't offer enough noticeable difference to really justify it unless you just happen to have the extra cash and want the added bling and just want to help someone out who is offering us an alternative part for our bikes.

Glad to hear you are back up and running totr..!

Map
dnut
 
Same here, I've been lucky with the ignition system for the most part, even tho I need to ditch my stock CDI unit before it blows my engine, I'm still in the early break in stage so I'm not riding it that hard yet but will be ready to soon... I do have a Rocket CDI here too, but hadn't had the chance to install it again since last time I had it installed I wasn't getting spark, come to find out it was a bad mag coil giving me problems. swapped back to the stock CDI unit and nothing so I measured the mag coil to find it dead open... on a brand new Dax bottom end. I changed out the mag coil for one of those new 2 wire coils and it fired right up, installed teh Rocket CDI and again... Nothing.
After this I took the Rocket CDI and had to cut off all the heat shrink and rtv I used to seal in the unit, checked the board and the compunents, everything looked good so I set up my old bottom end so I could test it, come to find out the red and black wires going to the coil were reversed and now it's firing nicely, just gotta put it all back together and re seal it so I can install it back on the bike.
I did wire it in and start the engine and give it a rev or 2 just to be sure it's working but now I need to permanent install it and ride with it to see how it does.
 
Strange... I've lost 3mph since I changed the mag coil. I don't have a good reason for that. I did not change the rotor magnet. Hmmm.
I also broke another rear spoke. Fixed that again. Did a great job on the true of wheel and sprocket at least.
 
Just for future info... The easiest way to check for spark is to remove the spark plug & also remove the boot from the wire, & spin the rear wheel (so that the engine is spinning too), & hold the tip of the wire near the engine head. (you will see a spark jumping the gap to the head)!

If you don't have a spark?, 99.99% of the time it's the magneto! (not the CDI (black box)). ;)
 
I do have a question. For whomever..but if the coil goes bad can it kill the cdi? I possibly could have 2 bad coils( i got a reading on one but its only to blue and white and its 325-340) but wouldn't think it could be 2 bad cdi's also. I couldnt get a reading on them but could when i put the meter on the spark plug wire screw and the blue wire. I even tried bypassing the clip ends and going to straight wires and couldnt. Any thoughts? THanks guys and gals for your helpful input.
 
JangAlang said:
I do have a question. For whomever..but if the coil goes bad can it kill the cdi? I possibly could have 2 bad coils( i got a reading on one but its only to blue and white and its 325-340) but wouldn't think it could be 2 bad cdi's also. I couldnt get a reading on them but could when i put the meter on the spark plug wire screw and the blue wire. I even tried bypassing the clip ends and going to straight wires and couldnt. Any thoughts? THanks guys and gals for your helpful input.
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When you say coil do you mean you are running after market cdi an coil which are seperate, or do you mean the magneto coil which is under the cover on left hand side of engine.

Stock set untilizes cdi and ignition coil combin d in one unit, helps to know for sure what you're meesing with.

Map
.wee.
 
2door said:
If you have an ohm meter, your dad will know how to use it, try this:

Use Low Ohm-Meter Scale About 200 Ohms

Magneto Coil

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

As for keeping water/dirt out. Make sure the gasket is good or seal it with a small bead of silicone and fill the hole where the wires exit the case with the same silicone sealer.

Tom
Click to expand...

Assuming you mean coil as in magneto coil...
I used this test to verify my magneto coil. my bad one had wacky readings, they would change as tested, so there must have been a short in the coil. My good one was still a bit wacky (maybe my meter has a problem) but came up very close to the figures. Give it a try, let us know what you come up with. Good luck.

As far a magneto killing a cdi goes, i suppose it is possible but doubtful. I can't say I've read of that happening. replacing that magneto is cheap and easy if all else fails.
 
I forgot that I was reading a conversation about aftermarker cdi's, Mapbike. In the midst of my troubles I was curious after seeing your post of different cdi's and your opinions on which ones were better and if actually paying bigger bucks would "help". Thats when I chimed in because I am not much of an electric guy. I was thinkin bout my chopper bike project and your opinions helped. And yes, I was talking about the magneto coil(stock). Thanks for the list, Radio. I had it copied down somewhere but I just got my tester again so we'll compare em' to the new ones i ordered. I was just pondering my issues and seeing if I could eliminate things to see how i can get spark after switching out everything. Seems I learn something new every day in this forum... hehe Thanks once again
 
JangAlang said:
I forgot that I was reading a conversation about aftermarker cdi's, Mapbike. In the midst of my troubles I was curious after seeing your post of different cdi's and your opinions on which ones were better and if actually paying bigger bucks would "help". Thats when I chimed in because I am not much of an electric guy. I was thinkin bout my chopper bike project and your opinions helped. And yes, I was talking about the magneto coil(stock). Thanks for the list, Radio. I had it copied down somewhere but I just got my tester again so we'll compare em' to the new ones i ordered. I was just pondering my issues and seeing if I could eliminate things to see how i can get spark after switching out everything. Seems I learn something new every day in this forum... hehe Thanks once again
Click to expand...

No problems and hope you get it lined out...

Yep always something new to learn no matter how long a person has been doing something.

Map
 
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