Compression Readings KZ440?

Hi Folks,
The question is about an '81 440 LTD I saw and bought the other day after passing one too many times

I'm told "it's sat for over 10 years" and has just over 10k miles on the odo. It was missing the forward controls and a few other parts which I've begun collecting/buying/sourcing.

Today (finally got a right control installed) I shot 5cc's of 20w50 into each cylinder, hooked-up a new battery (guage lights! woot!) and rolled it for a few seconds. Then did a compression reading...
I'm only seeing 85psi on each cylinder - identical readings.
From what I can search here, this is VERY low. Any ideas from the pro's here? Should i just tear it down now and rebuild? Why so low with only 10k on it? Any other suggestions?

Some background on me:
I got my "M" designation in 1978 and owned/rode four different bikes through the mid 80's. Then nothing until this little bike caught my eye. So it's been a long time and unfortunately, THIS bike didn't have it's owner's manual under the seat (but it did still have the tool kit!).

check your valve clearances before you tear into it. if they check out, try and get it running first and then recheck your compression to see if it improves, engine is probably a little "pickeled" from sitting and running it will bring it back up.