No spark YZ125G

[Mick N]

I have almost finished rebuilding my YZ125G-but no spark.I stripped it down completely -painted frame etc and put it all back together.I bought it a couple of years ago and it started but since then I have been working on it.My question is can a CDI unit or ignition coil just become faulty from lack of use?they have been sitting around for a couple of years.Does the coil need a bare frame to achieve a good earth?Any suggestions appreciated

[mainline]

I'm no expert on electrics (as someone will soon point out I'm sure) but I'd check all earth wires are grounded to bare metal and disconnect the killswitch if you're not absolutely positive it's working.

You may need something insulated (or someone else ) to pull the plug lead to stop the bike.

[head]

Yes the coil does need the bare frame as a good earth.

[Mick N]

thanks fellas will give those options a go first and go thru the process of elimination

[Mick N]

Ok I eliminated those two options but no change.I mucked about with it for the rest of the day but no luck. I went to check it the next morning just to see if the fairies had been working on it overnight and guess what-SPARK!No idea why or how.Well I put the plug in and it fired after about 3 kicks-first start in about 2 years.After a quick dance naked round the mango tree I tied all the wiring together and to the frame thinking my problems are over-then checked spark-none!Untied all wiring,checked connections-nothing.Mucked about with it but got nothing.Went to check it the next morning you guessed it- Spark.Could not believe it.I figured it must be a wiring connection so I wiggled the wires to the coil and CDI unit and found the spark come and went and then disappeared altogether when I wiggled the wires from the CDI unit to the ignition coil.So I thought I'd eliminate the CDI to see if that was the problem and replaced it with one from my YZ250H-the spark returned.Problem solved dodgy CDI unit I thought so I put the CDI back in the 250 and just out of interest put the "dodgy" one back in the 125 and what do you know -there was old sparky back!I've nearly torn all the hair from my head- and thats not much trying to solve this.So does anyone think this still could be a faulty CDI unit?Any ideas greatly welcomed

[Viper666]

Hate typing. Give me a ring and I'll walk you through it. Perko 0427334186

[steve7406]

Hey viper666 please give typing a go i;ve got exactly the same problem with my yamaha mx250.

[Viper666]

Steve,

Not up with earlier stuff but the basics are the same for most. Ring me.