My last gotta-stop-and-fix-it roadside repair was about a year ago. Our tandem dumped the synchro chain when we were riding on rough pavement (and I had not properly adjusted the chain tension for a long time - it was too loose). Luckily, because I had replaced the stock tension adjuster/idler with an very nice T-cycle adjustable idler (this is a recumbent tandem), I was able to remove the toothed pulley with a hex wrench, adjust the mechanism to increase tension a smidge, and then replace the chain on the front ring and pulley (making sure to have both cranks in phase) and then replaced the pulley and Off We Go!