Indian22 is right on the problem with the kits, most of the stuff sent with them is usually thrown away or not used. Don't use a rag-mount.That's my goal lol. Just to go for it and if I make a few mistakes, I'll definitely learn from them. The rag joint tensioner is the one I sent back, I couldn't get it to work right now mater what I did. "Junk" may have been a strong word. I'm sure someone must have had more luck with it or they wouldn't make them. My problem, aside from the chain compleatly shredding it, was bouncing. No matter how tight I set the spring it was just bouncing back and forth. Sounds exactly like you were talking about with tight spots and loose spots being the cause. Good eye seeing the valve stem like that, I didn't. The photo is from last year, and it most definitely DID cause a flat. As always, thank you Indian for your words of wisdom, it is most appreciated.
Measure your rear axle housing and get a sprocket adapter that clamps around the housing with a sprocket of your size choice that
is made for the adapter. MBRebel, ManicMechnaic, GasBike, King's Bike and many other vendors sell the sprockets and adapters.
You will need LokTite to make sure the bolts and adapter doesn't slip on the hub. The 1.5" housings with the coaster brakes and
the adapter seldom slips. The small 1" axle housings are a different story especially running a big 4-stroke engine.
GasBike for example has this for sale: