Still have cr 80 probs

[kjh1965]

Hi..still have fluctuating spark probs,sometimes large bright spark,sometimes weak spark and sometimes no spark whatsoever.Have had bike looked at by mechanic and now even hes scratching his head.So....what do we know?
1.The stator is fine,so is the spare one.
2.The pulse coil is fine..and spare.
3.Coil is fine as is spare.
4.CDI is fine as is spare.
All these have been tested,but not under load.The mechanic said the odds of all these failing ,and spares as well, are pretty long.We also put a new piston and ring set in as the old one was a bit worn.After we fitted the piston and ring it kicked over and ran for about two minutes...then died again .So,does anyone want to chuck their hat in the ring?By the way Ive just started to read up on the woodruff  key...is this possible? Anyway thanks for reading and any help would be much appreciated.I just want my son to be able to ride his bike!!! Cheers Kev..

[montynut]

Sounds like a bad earth connection between the engine and the frame and / or coil and frame. Have you painted the frame or powder coated it ? If so did you ensure that at least one of the engine mounts was back to bare metal and the same engine mount on the engine case was also back to alloy. Bad earths really play havoc with the CDI system.

You could run a temporary wire from the stator base plate the the frame connection of the coil and CDI unit. This eliminates the engine and frame as the earth path.