I thought I'd try to share my experience with motorizing this Murray Monterey Cruiser that I found on Craigslist. I used to be an avid cyclist, but I suffered from a medical condition in 2010 which has no cure and makes it excruciatingly painful to walk or pedal a bike. I haven't ridden since then. For mobility, I often use an adult Razor kick-scooter. I can use my right leg to push, and my left leg is essentially motionless. This is much less painful than walking and allows me to get around when I have to go places like my daughters' softball or volleyball games. I hope that this project can bring the joy of cycling back into my life. I'm sharing a little of my backstory so you will understand some of my motivation and also that I have major financial constraints. (Despite this, I intend to survive this project and will make safety a priority.) It is my first motorized bicycle attempt. My physical limitations also mean I won't be able to spend all day in the garage doing assembly. I have to pace myself and can work only in short intervals. I received my kit a couple of days ago. It's a generic kit from an eBay seller in California.
My first step was to begin installation of the rear sprocket rag joint. My kit came with the 3-piece collar and a 9-hole 44 tooth sprocket.
I plan to retain use of the coaster brake, and add a front (and possibly rear) rim brake.
Kit Hardware is GARBAGE!!
One thing everyone seems to agree on about these kits is that the included mounting hardware is worthless. As I began torquing down the 9 bolts around the sprocket I quickly proved this again by stripping the threads on several bolts.
My kit came with M6 x 1.00 x 40mm bolts. As I removed the bolts, I noticed the "spring" washers had no spring after being compressed and remained flattened. All of it went into the garbage. I don't have a good hardware store nearby, so I went to Home Depot. While metric fasteners were available there, they were outrageously expensive. (Just the bolts were sold individually at like $0.70/each.) So I opted for 1/4" hardware.
Since the rag joint had already been compressed, I was able to easily use shorter 1 1/4" long, 1/4" bolts. I also used new flat washers, spring washers, and nylon lock nuts. (These bolts about 32mm long vs the 40mm bolts from the kit. This left about 6 threads extending past the nut, vs about 14 for a neater installation.)
Without having any experience with this rag joint, I used my best guess about how tightly I should torque the sprocket. I just kept it as even as possible and adjusted any run-out by tightening an additional 1/4 turn or so on the bolts near the "high" side.
Coaster Brake
This bike has a Bendix coaster brake. My sprocket is dished or offset. I installed it per the instructions with the teeth closer to the wheel. My sprocket center hole was large enough to not interfere with the coaster brake cover. However, I did find it necessary to re-shape the coaster brake arm to clear the heads of the sprocket bolts. This was easily done by placing the arm in a vice and tapping on it convincingly with my favorite 3-lb hammer, "mini-Thor." Two main bends are required: 1 just beyond the square drive opening to let the arm clear the bolt heads. Then another near the anchor strap position to realign the arm with the chain stay. I'll take a photo of this and post it in the next day or so if I get to work on the bike.
I reversed the anchor screw so that the threads extend to the outside of the bike because I thought there might be interference with the drive chain.
Conclusion:
I think the result so far is satisfactory. I was able to achieve a reasonably true installation I believe (though if I had the money I'd probably use the 1.5" hub adapter and replacement sprocket.) I question whether I'll have adequate clearance between the tire and drive chain, and between the chain and coaster brake hardware, but I'm sure these issues can be addressed if/when they arise. I can reverse the sprocket if necessary, but I think in my case the "concave-in" arrangement will work best. We'll see!
My first step was to begin installation of the rear sprocket rag joint. My kit came with the 3-piece collar and a 9-hole 44 tooth sprocket.
I plan to retain use of the coaster brake, and add a front (and possibly rear) rim brake.
Kit Hardware is GARBAGE!!
One thing everyone seems to agree on about these kits is that the included mounting hardware is worthless. As I began torquing down the 9 bolts around the sprocket I quickly proved this again by stripping the threads on several bolts.
My kit came with M6 x 1.00 x 40mm bolts. As I removed the bolts, I noticed the "spring" washers had no spring after being compressed and remained flattened. All of it went into the garbage. I don't have a good hardware store nearby, so I went to Home Depot. While metric fasteners were available there, they were outrageously expensive. (Just the bolts were sold individually at like $0.70/each.) So I opted for 1/4" hardware.
Since the rag joint had already been compressed, I was able to easily use shorter 1 1/4" long, 1/4" bolts. I also used new flat washers, spring washers, and nylon lock nuts. (These bolts about 32mm long vs the 40mm bolts from the kit. This left about 6 threads extending past the nut, vs about 14 for a neater installation.)
Without having any experience with this rag joint, I used my best guess about how tightly I should torque the sprocket. I just kept it as even as possible and adjusted any run-out by tightening an additional 1/4 turn or so on the bolts near the "high" side.
Coaster Brake
This bike has a Bendix coaster brake. My sprocket is dished or offset. I installed it per the instructions with the teeth closer to the wheel. My sprocket center hole was large enough to not interfere with the coaster brake cover. However, I did find it necessary to re-shape the coaster brake arm to clear the heads of the sprocket bolts. This was easily done by placing the arm in a vice and tapping on it convincingly with my favorite 3-lb hammer, "mini-Thor." Two main bends are required: 1 just beyond the square drive opening to let the arm clear the bolt heads. Then another near the anchor strap position to realign the arm with the chain stay. I'll take a photo of this and post it in the next day or so if I get to work on the bike.
I reversed the anchor screw so that the threads extend to the outside of the bike because I thought there might be interference with the drive chain.
Conclusion:
I think the result so far is satisfactory. I was able to achieve a reasonably true installation I believe (though if I had the money I'd probably use the 1.5" hub adapter and replacement sprocket.) I question whether I'll have adequate clearance between the tire and drive chain, and between the chain and coaster brake hardware, but I'm sure these issues can be addressed if/when they arise. I can reverse the sprocket if necessary, but I think in my case the "concave-in" arrangement will work best. We'll see!