Never, EVER repair a cord like this! ALWAYS replace the cord with a new one!
1. The splice on this cord is not waterproof because there is no actual jacket there. Water + Electricity = DEATH!
2. The joint is weaker than the rest of the cable...if the cable gets snagged while in use, it would probably short cicuit.
3. Electrician's tape is notorious for coming unravelled over time, and thus will expose the wires underneath.
The absolute best thing to do is take the saw apart, buy a piece of cable the desired length with a grounded plug, and replace all. If this repaired saw were being used on a work site, OSHA would impose a rather hefty fine.