1983 cr 500 no spark?

My 1983 cr 500 has been sitting in the shed under a cover for 20 years....it ran well when I left it. I have decided to get it fired up ....... things like airfilter and chain protection plastic have just disintegrated, but the main thing is there is no spark but there was one when I stored it? I think it must be something simple like kill button stuck or something but it is not that. Any ideas? Why would or could sitting under a cover stop spark? Spark plug cap looks okay and is original no condensation inside apparent.

Try checking the grounds from the stator to the coil .

I have a multi metre but don't understand this stuff. Can you tell me how to do that....walk me through it?

I can try , can you post a picture of the meter you will be using ?

I was going to suggest test the grounds with a meter first so I’ll do my best to pass on what I know .

Here is the multi meter

I pm’d you yesterday .

Trim your spark plug lead about an inch of you have that much to spare, common issue and costs nothing.

Thanks. I have cleaned the inside of the stator, checked the kill switch, cleaned connections, took quarter inch of sp cable and got erratic spark. Will take more off cable and attempt fire up this week. This bike has a compliance plate and is an xc not cr.

Motoplat?

Yes. Motoplate with flywheel, not the CR motoplate. So it's a XC 498 motor but in a CR frame with a rear loop added to the rear subframe in case a rear mudguard with light required. This combination gave CR performance with a smooth motor. Have not started in for 25 years.
Cut 1 inch off plug lead....have spark but not greatest......as carbi not drained when stored it had to be cleaned so not sure if carbi or spark holding it back from starting. COVID-19 project?

Surprize said his friend sprayed some eithr/starting fluid in the open carb to see if it was ignition or carb, Fire off carb, nothing maybe ignition. Sage advice!! Wonder what he's up to this winter?

How about the plug? I recently had trouble getting a strong spark so I bead blasted the plug followed by 130 lbs of clean compressed air. Result was a hot blue spark so I did the same with five used plugs laying on the shelf that all had a weak spark and got the same result.