Ok, you know that wd40 will clean off any grease that's there to protect and lubricate the chain's?
If you use wd40 you'll need to reuse it after about 5 hour's of bicycle riding, and about 15 minutes of motorcycle riding, it also causes premature wear .
Not good stuff to use on bearing's or chain's, but in the end it's up to you what you use
It is ok to use as a protectant though, spray it on your engine etc and wipe off any excess.
That's what it was originally designed for in the military, the high fish oil content help's to prevent rust.
The standard chain's that are supplied with cheap pit bike's stretch easily and fast.
If you don't keep an eye on the tension it might jump off the front sprocket and smash your stator cover and stator.
There are quite a few cases of that in the thread's here