Forty-two-year-old John dominated the race by leading from start to finish and riding a Mugen Shinden in the race, set an incredible new lap record of 117.366mph.
The race was expected to see John go head to head with team-mate Bruce Anstey but as early as Glen Helen, nine miles into the lap, he was edging away from the Kiwi with his lead already 4.9sec.
He increased his advantage at every single timing point and eventually took his 21st win and 42nd TT podium by 23.3sec, his new lap record an impressive one minute and 21 seconds inside the old mark.
John, who has been hampered by a recent wrist injury, had opted out of yesterday’s Supersport Race 2, but was delighted with his electric bike success
“The Zero bike takes a lot less out of me as I’m not having to wrestle it around so much,” he told the Belfast Telegraph.
“But I wasn’t hanging around and I was probably going through the corners 10-15mph quicker than what I was taking them on the Superbike.
“The bike was phenomenal and although it’s a shame there wasn’t more bikes out there, I gave it a really good go.”
Yesterday’s postponed Sidecar Race 2 will now take place today from 12.15pm.
John is now just five wins away from Joey Dunlop’s all-time record of 26 TT wins.