TTR50 bike won't start, bad CDI?

Hi all, I'm new here... I have a 2012 Yamaha TTR-50. I bought it used two months ago and have been enjoying watching my boys use it. I went to take it out last weekend and it wouldn't kick-over. The worse part about this is that it started when i left the house. I drove 4 hours to go riding. When we arrived it wouldn't start. Talk about disappointment.


The start motor works fine. At first I was thinking it was just flooded. I then checked the spark plug and what I've noticed is that it only creates a spark when i first push the start button or when i release the start button. If i just hold down the start button and let the starter motor crank there is no spark. I replaced the spark plug with a new one but this didn't change anything. I would think the coil would be fine since I'm seeing a spark when i first push/release the start button, but thinking possible the CDI may be bad with the erratic nature of the spark . Any thoughts would be helpful before i go spend $100 on a new CDI. The starter motor will not engage unless i have it in neutral and the kill switch is off along with the ignition in the on position so I think i can rule those items out since the start motor is engaging. I've also check the battery and its fully charged.

Maybe a bad connection somewhere? Have you double checked all the wires? There could be a bad connection to the CDI, or to the earth on the bike. Just a few things to check.

Yeah, i've reviewed the connections and nothing found yet. Going to try testing the coil with a OHM meeter to rule that out as a problem.

I'd be interesting to see the results from that!

Well I figured out the problem. It was the CDI as I had suspected. I ended up testing the coil and the ohm's seemed OK, i decided to swap the coil i had on a Chinese ATV that appeared the same and put it on the TTR50. It still had the same results as before. This is when i concluded the coil was working fine. The only other thing left was the CDI by process of elimination. I end up dropping around $100 for a new Yamaha CDI. Plugged it in and the thing started right up like it was new again. Thank heavens that mystery is over. Now i just hope it doesn't happen again. I can't afford a new CDI from yamaha every couple of rides. 

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