cr 85 no spark

Start by replacing the spark plug. Disconnect the the kill switch wire. Inspect the wiring harness for bare, shorted or broken wires. Check all ground connections. Inspect the generator coils, and the trigger coil for damage. These are under the flywheel on the stator. Check the resistance of the coils and compare them to Honda specs. These specs can be found in any good service manual for your bike. Check the flywheel key to see if it sheared when the nut came loose. Check the magnets on the flywheel to make sure they are good and strong. Check the resistances of the primary and secondary windings of the main ignition coil, the specs should be in the book. Check the high tenssion lead and the spark plug cap. Some spark plug caps have resisters in them. If all of these components check out good with no shorts or broken circuits, try another CDI module.

Considering they flywheel was an issue to begin with I'd start with that side of the electrical system. Yes you might have damaged the pickup, maybe pull it and make sure it's clean then set the sir gap just like a set of points. Take time to make sure none of the wires got broken or split and might be grounding out. If still no spark THEN start with the usual suspects.

Just had the same problem myself. Ended up changing the Plug, CDI, Stator and finally the Pulse coil. All is running now.
However, I ran the bike for about five minutes and then it just died on me with no spark again. Luckily a mechanic was on hand who started looking at the air filter. He told me not to oil it up (despite what people say) when cleaning as this just ruins the spark plug. I gave it a good clean (no oil)-another new spark plug and hey presto the things been ok since.
Hope this helps.

You sure should oil that filter because it's a lot cheaper to spend a little bit getting the bike jetted properly than rebuilding the engine. Lot's of folk over oil filters and pop them on and expect the bike to just run which causes them all kinds of problems, maybe try a little less oil?

What oil and how much do you use Patman

I have almost always used Amsoil Dominator for premix. When I ran it in my 360 KTM I mixed it 50:1, when my son started on 2 strokes (KTM 50, CR85, CR125) I settled on 32:1 for all the bikes except my Montesa 315R but I used special fuel for it anyway. Most any decent premix will provide plenty or protection so just pick one you can easily keep in stock and stick with it. In the trans of my 2 strokes (except the 315R) I have always had great results with a Type F automatic trans fluid. Again most any will work fine as long as you change it.