Changing gearing for the first time on a used LO206 (old OTK chassis). Should the chain brush up against the frame? Ideas on how to adjust? I can add some more details if needed.
Sometimes this will happen depending on how the crossbar behind the seat is positioned. One of the differences with “four stroke chassis” is the position of that bar.
It’s not something to worry about other than being cosmetic, assuming you don’t run it for so long you saw through the rail
Move the clutch drive outboard (assuming it might be inboard already)
Wrap something around the rail where the chain is hitting. A piece of heater hose, cut, placed over and zip tied is surprisingly durable. Solid nylon or similar even better.
You can play with sprocket sizes too. Run larger driver sprocket and smaller axle for a given ratio.
Re-locate the rear crossbar. Kinda extreme, but people would often do this with CIK chassis 5 or more years ago before 206 marketed chassis became popular.
Another option is if you have the ability to move the engine back a touch, you can shorten the chain which will change the angle and may clear the cross bar.
We run a 206 on a 2014 OTK. Needed to run driver outboard near seat. There is also a bit of offset on our JTP mount. We’ve run 16-18T drivers and 57-67 rears without a problem for almost 2 years. One nick in the crossbar from when we threw a chain after dinging a sprocket on a curb.
The only machining we needed to do was to lathe extra material from our gear carrier for cleance from the third bearing bracket.
Even your chain pics look good