There is a Harbor Freight tool store at KANNAPOLIS, NC. I don't know just how far that is from you but they have inexpensive knock-off's of Dremel tools, and a variety of stud extractors. Big sale in progress there this month too.
Bikeguy Joe has a post on making these China Girl motors more bullet proof. Refitting these motors with some grade 5 or 8 cut off bolts where a Dremel wheel could cut off the head and dress the threads to make good durable studs for intake and exhaust & mounting might be worthwhile. I'd imagine even head bolts too if you can find bolts long enough for the conversion. (Tractor Supply ?)
Bicycle Motor Preperation And Care
Some may see the merit of a flat washer placed on the stud first, then a lock washer with the nut tightened down to 15 flbs.
Speaking of Tractor Supply, Mr Right1_99 has a thread on a better spring loaded chain tensoner here:
Motorized Bicycle Spring Loaded Chain Tensioner
So, if ya got the motor off the bike, now's a good time to consider upgrading the studs & fastenings with grade 5's or 8's. The head bolts could be done later with the motor in the frame probably. (just whatever you want to do...perhaps wait till warmer weather for that)