The trick to keeping the chain 'out of your spokes' is to keep it on the sprocket in the first place...
First, you need to make sure the sprocket is mounted so that it's as close to perfectly centered
as possible & has no 'side to side' wobble
. (It also helps to file the sides
of the sprocket teeth so that they can 'feed' into the chain without catching the sides of the links & causing the chain to snag & derail.
It's also very important that the tensioner feeds the chain straight
onto the sprocket & then put a screw through the tensioner
into the frame rail to keep it from ever moving.
Follow these steps & you will be okay!
Also... don't use rubber mounts on the engine! bolt it as solid as possible so that it can't ever move!
I've built hundreds of bikes all with the stock parts & I've had very few problems with the chains.