Hi all, been a while.

Both bikes are currently poorly in the garage, one is carbs (shock) but this one is more complex.

I've had electrical gremlins with this one for a long while with various different symptoms. I've replaced pretty much the whole charging system up to this point. The last part I changed was the reg/rec, not wanting to chance getting a duff one off ebay, I purchased a pattern one from electrex world:

http://www.electrexworld.co.uk/cgi-bin/ ... RR17#aRR17

Between buying that and fitting it, there was about a month before I got around to getting a new battery and getting chance to fire it up, so I can't 100% recall if that was all I changed at that time but I'm pretty sure it was.
Initially it fired up but immediately cut out. I thumbed the starter again and let it spin over for a while when I noticed smoke coming from the back end of the bike…balls. The CDI had fried.

A call to electrex world and I was assured that there is no way a reg/rec would fry a CDI and he told me to check a couple of other bits that are way beyond my mechanical ability. I passed the job on to my local, very knowledgeable bike electrician who checked everything, advised that I should change the battery in case it's spiking and probably swap the generator for another one I have from an expired engine. This done, I lucked out on finding another matching CDI from my local breakers for £20, I checked it didn't smell of burnt electrics before handing over money.

Back at the shed, CDI installed, bike turned over but didn't even try to fire. Smelt the CDI, burnt. Feck.

So, thoughts? Here are some pics for people that may know what they're looking at.

First, it sounds like you know what you're doing overall. You probably do good maintenance. But in spite of this you've gotten the same results from separate CDIs.

I would bet that your issue is something basic, like a mismatch in the bike's wiring harness (example: 12 volt power on a wire that shouldn't have it).

You've shown that you can "key-switch" the bike to "on" without causing the CDI to burn up, but when you crank it (and the R/R begins producing power) the CDI starts smoking.

When you turn the key to "on" you're powering up every part of the bike's electrical system except the R/R (the only other thing that changes (for the CDI) when you go from "on" to a running engine is that the trigger wheel pulse generator (variable reluctance sensor) under the left-hand side engine cover will be producing voltage).

Thanks STS.
Is there really enough power coming from there to bugger a CDI? I would never have guessed that. Is there a way I can test the output on this, does anyone have any figures?

So in order to not knacker another box, I should stick on a different reg rec and inspect the wiring to and from the pulse generator, then fingers crossed.