Allthread and chain solution
I was having a problem keeping my chain taut, and was very unhappy with the stock chain, so off to Tractor Supply for some #41 chain. Got the chain and got to browsing and also picked up a really sweet ball bearing, rubeer coated chain trensioner, AND spring, it is sold seperatly. After mounting the chain I took some 3/8 althread rod, heated it up and bent it into a U shape to fit around seatpost. I cut a strip of metal ( out of stock tensioner mount) to secure allthread. Then I just mounted the spring tensioner to the end of the allthread, the ID of the tensioner seems to be a good fit on 3/8" rod. Then a little adjustment and done. Spent $40. on everything including new chain. I have put a couple of miles on it an it is a lot quieter, and very smooth...
That is a supurb roller no doubt. I bought everything except the spring (out of stock) and started putting it together. The first thing was bending the allthread, even with a blowtorch and oven mitts, it was nearly impossible to bend. When i did get it around the right shape, the apex had cracked from stress. I also took a few teeth off my hacksaw cutting it.
After i gave up in the allthread, i used the tensioner bracket, drilled to 3/8" cut one end off and used bolts. This almost worked but the screws from the engine got in the way of aligning the rolller, it also pushed the "bottom" chain too close to the " top" chain.
After that failed i tried to mount it where the original one went. This was working fine untill 10ft later the chain had grabbed the roller and bent the arm.
As a last resort, i took out another 2 links of my chain and loosened the back wheel nuts. I originally didn't think i had the wiggle room for my wheel. Put the master link in, pulled the wheel tight and straight, tighten the bolts and Presto! My first bike finally works perfectly!
I would recommend taking out links with a chain tool ( i used a bike chain tool for #50 chain, still worked out okay) than wasting time with a tensioner