Originally Posted by
BassNotBass
I agree with Squid's chain slack comment. One thing about these inexpensive drive trains is that they aren't close to being machined well and true so even with brand new components there can a be a noticeable change in chain tension as you rotate the cranks. Always adjust the chain tension/slack at it's tightest point. Chain slack is also a good reason to stick with the traditional single speed 1/8" width drivetrain instead of opting for 3/32". The 3/32" chains are usually intended for derailleur drive trains so they're designed to flex laterally a little to make shifting and jumping from one cog to another possible. This is often the cause of a chain jumping the chainring on a single speed if chain tension isn't tighter than you would normally run it. This was a common problem during the fixie fad when people were doing the cheap road bike to fixie conversions.
I have a new chain that is the 1/8 chain, I'm going to install it and hope that it stops my chain from jumping, the bike made it approximately 40 miles before the chain decided to jump off of the sprocket. I might eventually do something that seems taboo for the Cruiser purists and put a hand brake at least on the front or rear wheel, it's pretty unsettling to have your chain pop off @15mph with no way to stop! LOL Otherwise, I love the simplicity of riding a single speed coaster brake beach cruiser. I usually ride road bikes and it's fun to get on them after a few days of riding the cruiser.