Hey guys, I rescued a 74 MX175 from a barn about a year ago and had been running great. Last week after riding for about 15 minutes, it shut off on me while idling and refused to start back up.

I pulled the spark plug and found I was getting no spark.  I disconnected the kill switch and still had no spark. Hoping it was the coil, I ordered a new one and installed it but still no spark.

I’m pretty mechanically inclined but I’m rather weak in diagnosing the electrical side. At this point I’m thinking it’s the CDI box, but am not sure how to pinpoint the issue. If it is the box, I’ve been looking into the CDI fireplug, anyone have experience with that?

Greetings from Tennessee  
  hopefully others will chime in with cdi info

It might be best to resistance test the stator coils first?  Yamaha pulsar coils tend to fail on early CDI's.  Specs might be hard to find for that model though...  I will dig through my papers and see if I can find them.

Another thing to check is connections...  many members have had spark come back just by cleaning the connectors or even just unplugging and reconnecting the CDI plugs...  I like Caig Deoxit for electrical connection cleaning, works miracles (but not likely it would help with this problem unless connections are dirty)

CDIbox.com fireplug products have been discussed here many times for other models.  You can do a forum search...  never heard anything bad about them.

 

Thanks man! Just ordered a pulser coil too

Update: bike is back up and running after replacing the primary and the pulser/trigger coil

Where did you find the parts?  Can be hard to find replacements for old CDI's so it might help someone else if you can let us know.