Motorized bike build

Well shoot, I was hoping I wouldn't have to do any modifications or machine work. Does anyone know if I could install a rear brake without having to do the modifications depicted? I thought I could just use the hole the fender was attached too or drill a hole and mount. I don't have a machine shop, lack the experience/knowledge and don't have too much money to do modifications like that so I'm hoping there is a more simple way? I thought adding rear brakes was as simple as finding a hole and mounting.


I may be forced to go with a rear coaster brake
This example is on a 27.5 mtn bike with an 18 inch frame.

I had the long reach calipers that just weren't long enough when attached to the cross brace. I used two aluminum plates cut a little longer than needed and drilled a hole for a bolt to go through the cross brace and the plates. The plates don't need to be as thick as what I used, just what I had on hand.

I drilled a couple more holes near the bottom and closer to the seat stays to help clamp it all together. Once this was done, I drew a line of the angle needed and cut them to fit. Finally positioned the caliper and marked and drilled the hole.

Not difficult or particularly skilled work. Just takes some patience and taking things step by step. I hope this helps to show that if you are methodical you can do things like this with simple tools.
 
cart-before-the-horse.jpg
 
-- So does anyone know if there is a max load for the engine that I'm looking at? Would I be better of going with a 48 tooth or higher sprocket / rag joint versus the 44 tooth sprocket and hub adapter? I'm 350lbs and hoping I can ride, but will be a bit disappointed if I'm too heavy. I know if I'm a bit heavy for the bike, but once again am wondering if there is a max load for the engine
 
Without taking any consideration for weight limits on the bike…I’d try a 44.
All the motorized bicycles usually require some degree of pedal assist.

A well tuned 66/80cc should be able to roll your weight once it’s in motion. Just be sure everything about your bike is capable of handling the extra weight.

I had a friend who weighed closer to 400 than 300. He had and rode a motorized bicycle fitted with a small 4 stroke engine. He had to modify and reinforce the seat pipe to accommodate his size. He used 3/4” galvanized water pipe. I’m pretty sure his bike had a 44T sprocket and that engine wasn’t more powerful than a 66/80cc 2 stroke.
 

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