Coil Insulation Leaking Spark

My 2009 YZ450 engine has come back from a rebuild, but will not start.

I've cleaned the carb, and put in an iridium plug, but still no joy. On kicking it isn't completely dead, but never takes at all. It has some backfires, but never anywhere near starting. I tried tow starting it, and nothing at all (worse than kickstart - I'd guess it just became flooded).

I have a question on the coil.

What I did:

To check the spark, and generally draw things through, I took the plug out and pushed it down the road with the coil laying across the top of the frame with the plug in.


The spark was great. Even with the end of the plug held back from the frame slightly, it was jumping at least 1/4 of an inch between the plug and the frame, no problem.

However, when I laid the coil across the top of the frame, with the plug not earthed, at some positions a spark could be seen coming out of the coil itself, about half way up the tube, into the frame.


Is this normal, or does it indicate some kind of failed coil insulation that will be leaking HT when installed in the bike?



Sounds like the coil is cracked. Replace it.

Thanks for advice!


Having real trouble sourcing a replacement coil locally (Riyadh / Abu Dhabi). Looked into getting one shipped and looks like it will take weeks.

So... Thinking about trying to repair it. Even just to confirm it will start, so I know it's not something else.

Having taken the rubber end off, there is a small crack (see attached)



Would epoxy glue be a good enough insulator?

- Any other ideas?



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