Home made chain tensioner, using a Baja Bike roller and arm, and the matching spring. I bent the spring there a little to accept a master chain link,

hey i like the set up but were did you got the chain wheel and is it have bearings inside

The neoprene roller is permanently mounted to the brass arm. There is a sealed bearing inside the roller (good quality, not a bushing).

The roller&arm and matching spring are available at Tractor Supply Co, maybe Ace Hardware, and at some go-kart and motorcycle stores that carry Baja Motorsports brand.

Here is the part number for the roller ($15) The spring is about $3.
5510238 roller

5510254 spring

When I ordered that screw, I had to order a few to get it. I may have some extras. I'll message you if I find some the extras and see if you want me to send you one. They were very hard to find (metric lonnnnnng screw with same thread pitch as the china stuff.

You could cross thread an American screw in there but I try to keep stuff the same.

I am still using this tensioner, and it works fine if only used as a vibration damper and to remove a very small amount of slack (such as chain stretch). The screw must use a nylock nut or 2 locking nuts to be sure the tensioner is secured. Mine got quite loose one day with only 1 nut, and still worked, but did shave some of the rubber off the wheel. Now I have 2 nuts and threadlock, and have no more problems.

I plan to solder a cable end on there to replace the brass stop.