Engine Trouble -no spark- troubleshooting magneto & CDI



it's been getting difficult to start, we've had some humid weather, so no biggy, i thought. last night, it just quit, hasn't started since.

ok, at first i thought the magneto got wet, so i put a space heater to it for a while...no change.

i removed the plug, used a metal strap to ground it. pedaled, no spark.

i wired a light-bulb to the white-wire & pedaled, it lights up. wired bulb to blue wire, not even a flicker. of course, i don't think ignition can be checked that way, just covering the bases. how can i check the blue wire for power? keep in mind i have no meter to work with.

the key, i think: is it possible for the white wire to have power, but not the blue?

magneto or cdi? i vote cdi...opinions? when i can afford a part, i'll only be able to afford one or the other.
the blue and white wire are connected to the "coil" on the magneto. the black wire is a ground. So pretty much the blue wire should have power coming out of it, and to complete that circuit must go through black wire (ground), and if it doesn't, magneto is prob. fried. I had to get a new one a couple is weeks ago and it worked fine after that. I also had no spark, so i orderd a new CDI first, still no spark, so i order a new magneto from dax, and it worked fine after that. I also had a new champion spark plug, too.


i used alligator clips & an auto dashboard bulb & fitting.


i get light with white/black and blue/black...yay!

CDI is the culprit.
well, i bet this one didn't go bad so much as suffer damage...sometime during the last coupla months, never could figure out what exactly happened, some insulation was worn off the wires right where they leave the cdi box, and there were a few wire strands torn also, too close to the box to do a real repair. i used some liquid electrical tape & it seemed fine, but i think the remaining wire strands finally shook loose under the repair.

today's troubleshooting confirmed that, i'm pretty sure.
i got the CDI today, but i still have a problem, actually i had a few but i fixed the others.

wired the CDI in, pulled the plug, cleaned it, gapped it to a solid .030. pedaled, it wanted to spark up briefly. it did that a few times, sputter without really firing up. ok...checked the plug, it was sopping wet.

taped the plug to the exhaust and connected it, pedaled. very light & weak spark. i'm thinking to myself maybe it's just because it's still light outside and i couldn't see it very well, but it sure didn't look strong enough to ignite that much fuel.

pulled the carb. first thing i found was the top tab on the carb was broken off. closer inspection proved that the edges on the clamp is what breaks the top tab. file off the little locater-nub and use a hose clamp before yours breaks, too.

disassembled the carb. the brass float/needle bracket was pretty closed, i'm thinking maybe i'm constantly flooding it.

this is how i adjusted my float level: turn the carb upside down, push the tickler all the way down (up), use a flatblade screwdriver to reach in & lightly spread the gap, just until the tickler will still make about 1/16" contact with the bowl. to me, that looks just about right.

ok, let's dry everything out...plug out, carb off, clutch engaged, pedal pedal pedal. while i was doing that i reached down and put my thumb over the intake...boy, these things really draw air!! (after feeling that volume of air-intake, i knew at sea level i could go to the 3rd slot down for a good mixture, providing i can get it running at all)

put it all back together. used some zippo lighter fluid for a quick prime before screwing the plug back in. it sparked and ran for about 5 seconds, til the real fuel hit it. which leads me to the only question i have left...

can the magneto be intermittent or weak but still appear to be working?

(i just had to go try it once more before i clicked "submit" :LOL: )
intermittant problems are the hardest to solve :(
sounds like the problem I was having tho
mag worked when wanted to ...then not at all