I hope you gave that plastic as much texture as possible. JB weld on that kinda plastic doesn't strike me as a winning combination. Maybe it's gonna work great, I haven't tried it.
If you get disappointed, you might check out a white cutting board. The thinner ones seem harder,IDK if that is true, not a scientific observation,
YaKnow, JB weld on a Very clean and surface prepped area And a shaped and sized piece of plastic, with some small holes that are opened up wider at the top, so the JB is like a mushroom shape, leave the plastic long enough to heat and curve it so the chain slides up the bend on first contact.
You getting a picture?
Think it might work?
You have already taken steps, play it out. If it doesn't fly,Meh, step back and take another swing.


If you have room to build a bracket to clamp down and use a thick enough piece so you can drill a 1/8" hole and a hole wide enough to set rivets and leave plastic proud of the rivets.

JOG, good points. I roughed to the plastic and metal to give it some bite. Hopefully it'll hold!

Gary, that makes sense. I had 7/8 free play, but that seemed to tight, and I was worried it would stress the transmission shaft. I loosened it to 1.25", and it seemed much better.

If anyone has the chain conversion, what's your slack?

The stock speedo runs off the output shaft of the tranny. When you change the final drive ratio, or rear tire size it throws it off. (worse than it was stock)
I went from the stock 2.98 to a 2.60 with a 150/90 15 rear tire and 100 miles on the stock speedo was 123 on a gps! But I'm only turning 3400 at 60 mph.
Check yours aginst a gps app on your phone.
Speedhut makes some great gps speedos, not cheap, but I love mine. (cept when I go thru a tunnel )
15-52 is 3.46, still lower than stock 2.98. Faster takeoffs, but a lot of revs at highway speeds. Stock with 2.98 turns about 4100 at 60 mph.

Check your rpm at 55 with your final drive, rear tire combo. Fewer revs means less vibration and better mileage.
With 4th gear so close to 5th on these bikes it can be a great passing gear, leaving 5th to be used as a overdrive highway gear.
Mine is about 3200 at 55 and I can see with my mirrors. If I need quick power I just drop to 4th.
( 4th and 5th are both overdrive gears if you look at the ratios, hey the bike is a thumper after all.)

Update: 15/52 seems perfect; no chain rubbing, smooth at 55, accelerates like a missile. I took a 38F ride today and was loving it! No more vibrating like a bed at a cheap motel.