no start condition

I pulled my bike out of storage couple weeks ago and started some spring maintenance. The bike in question is a 1995 Yamaha DT200. I pulled the carb off, disassembled, cleaned, and reinstalled. Grabbed the battery from inside the house where I stored it over the winter and hooked that up. The bike fired second kick (no electric start on this bike) and ran beautifully. I let it warm up for about 5 minutes and shut it off. I came back to the bike a few days later and it wouldn't start. Noticed the power valve servo motor wasn't cycling when keying on. Used a DDM to check voltage on the battery and only 5 volt (12 volt system) I never had a battery tender on the battery over the winter and am going to buy a new battery this week.

My question: Is this most likely the cause of my no start condition on this type of bike? And why? power valve open causing poor compression???

well i've ordered a new battery from interstate prices at 40 bucks and picked of a trickle charger after work today. i have to old battery charging right now and later tonight i'll see if it has enough of a charge to start the bike. if it starts i'll check the charging system, my manual says i should see 13.3 to 15.3 DCV at 3000 rpm.

hooked up battery after few hours on the 1A trickle charger, didn't fire, found plug fouled, changed plug, and fired right up. Check voltage at 3grand rpm and 14.7 volt. Good to go. Still going to install new battery keep other one around charged as a spare.