Michael Dunlop sits one behind Joey Dunlop's all-time Isle of Man TT record of 26 wins after securing the third four-timer of his career at the event.
Dunlop won Wednesday's Supersport race to add to his earlier victories in the first Supersport outing, the Superbike race and the Supertwins opener.
The 34-year-old will compete in three further races this week.
For the Ballymoney rider, it was his 11th Supersport class win as he repeated his 600cc double of last year.
The MD Racing rider has now won seven of his Supersport successes on Yamaha machinery and he and runner-up Peter Hickman both recorded the first 130mph laps ever achieved in the middleweight class.
Michael's previous four-timers came in 2013 and 2014 and he has the chance to add to his overall tally when he takes part in Friday's Superstock and Supertwins races, and Saturday's 'blue riband' Senior TT finale.
Another win would see him draw level with his legendary uncle's total of triumphs and also match Ian Hutchinson's 13-year-old record of five victories in a single week.Spanish rider Torras Martinez killed in TT crashDunlop wins Supertwin to inch closer to all-time TT recordHickman storms to Superstock TT triumph
Dunlop led Supersport race one from start to finish on Saturday and he repeated the feat in race two, ending with a 9.6 seconds advantage over runner-up Hickman, with Dean Harrison a further 24.8 seconds adrift in third.
The leading trio all broke Dunlop's one-year-old lap record on the final lap.
Dunlop was fastest with 130.403mph, Hickman registered 130.219 and Harrison lapped at 129.697.
The race followed a now familiar pattern as the Northern Irish rider made a break for it from the offset, building up a lead of 6.6 seconds over BPE by Russell Racing Yamaha rider Harrison after the opening circuit courtesy of a lap of 128.809.
By the end of lap two, Hickman had assumed second place on his Triumph, trailing the race leader by 11.6 seconds, but having a 5.4 seconds cushion over Harrison.
Hickman started reeling the Ballymoney man in on lap three, reducing his deficit to 8.1 seconds as the riders set out on their final 37.73 miles but Dunlop managed his lead to come home first.
"I had a wee bit of a gap, built a comfortable lead, but knew the Triumph had a bit more power, more 'cc's.
"I knew I had to ride the Yamaha to its full potential but the wee bike was great. I can't thank my team enough.
"When the gap came down to eight seconds I knew I had to push on and upped the game.
"To do the 130mph lap is pretty cool, I knew I could do it, I'm always trying to push the boundaries."