But the question of Cooper's fight back chances was already being resoundingly answered as he emerged from the forest close on Rees' tail.
After the refuel the leading quartet of Rees, Cooper, King and Smith left the pits within sight of each other for the next 40km of riding.
Cooper made the pass for the lead late in the second lap and reached the halfway pit stop with about 18secs advantage over Rees. Smith had been sidelined on lap two with clutch failure while Cooper's Suzuki team-mate and 2011 runner-up Rhys Carter (Papamoa) had moved up to fourth spot after some similar startline issues.
On lap three King passed Rees when the young Honda rider crashed and lost a few seconds while Carter retained fourth. Tauranga's Reece Burgess (Husaberg 450) and Aucklander Karl Power (Honda 250) completed the third lap in close company battling for fifth spot.
The final lap saw Carter improve to third spot ahead of Rees while Cooper completed the race in 3 hours 15 mins 35secs and with a 1m 54secs margin over King.
Cooper said pre-race practice with warming-up the bike to prepare for the dead-engine start hadn't shown up any problems.
"I was left at the line and when it finally started I put my head down and passed as many as I could before the trees," said Cooper. "A lot of guys were really good and they let me past, but not everyone."
The move which took the lead away from Rees came toward the end of the second lap. "I followed him till over halfway around. Once I passed him I was able to check out a little bit," said Cooper.
But the eventful race wasn't quite over for the 2011 MX1 national motocross champ. "I had a huge crash on the last lap but I got the bike started and going again," said Cooper.
King was pleased to win the 250cc 2-stroke class as he prepares for the World Veterans Motocross Championship in England next month.
"I just wanted to have a good safe race and hopefully finish on the podium," said King. "These were the best conditions I've ever seen for the race. The track must have had 30km of black-sand trails which were a lot of fun - just like a motocross track apart from only being a couple of metres wide."
Carter's ride almost mirrored Cooper's effort with similar starting problems putting him 60th after the sprint around the start loop.
"It took about 10 kicks to get my bike going," said Carter. "Luckily I was able to pass a lot of bikes before we got into the trees. In some ways the race was harder than last year and in some ways I found it easier. The sharp edged bumps made it really demanding but I'm feeling fitter and stronger than I was last year."
Teenager Rees - who was contesting the T100 for the second time - completed his impressive ride 40secs behind Carter in fourth. Burgess was the best of the specialist enduro riders for the second year running bringing his 450cc Husaberg home in fifth position.
Young motocross racer Callan May (Auckland) won the battle of the small-bore bikes on his Yamaha YZ 125 finishing ninth with Rotorua's Scott Birch completing the top-10 on a Honda 250.
Tony Rees Honda Tarawera 100: 1 Cody Cooper (Papamoa) Suzuki RM-Z450, 3h 15m 35.542s; 2 Darryll King (Hamilton) Yamaha YZ250, + 1m 54.195s; 3 Rhys Carter (Papamoa) Suzuki RM-Z250, +2m 27.877s; 4 Mitchell Rees (Whakatane) Honda CRF450, +3m 16.621s; 5 Reece Burgess (Tauranga (Husaberg 450) + 4m 43,439s; 6 Karl Power (Auckland) Honda CRF250, + 5m 39.244s; 7 John O'Dea (Napier) Husqvarna 250, + 7m 28.262s; 8 Conrad Edwards (Ohope) Honda CRF450, + 7m 29.843s; 9 Callan May (Auckland) Yamaha YZ125, +9m 25.839s; 10 Scott Birch (Rotorua) Honda CRF250, + 12m 36.114s.
Cooper in motocross
Cody Cooper is back on motocross duty this weekend racing at the seventh round of the Australian MX Nationals at the Horsham track in Victoria.
Cooper is fifth in the Pro Open class standings - his most recent performance at the Hervey Bay round in Queensland on July 1 providing a mixed bag of an eighth followed by a a moto victory and then a crash in the final race.
Kiwi Josh Coppins (Yamaha) leads the Australian title with four rounds remaining.
Kelsey sets the pace
National rally championship front-runner Alex Kelsey won the Motorsport BOP two-stage rallysprint in the Mamaku Forest on Sunday.
With the event starting in a heavy frost and -2C temperatures, it was the Subaru Imprezas of Coromandel-based Kelsey and Tauranga driver Ben Thomasen which set the pace.
Both produced their combined best runs on the third pass through the 9km "out-and-back" course on sections of Ngawaro Rd and Galaxy Rd.
Kelsey's final effort secured the win by almost 13secs from Thomasen while Toyota Starlet driver Mitch James (Tauranga) led the 2WD contingent and finished third overall ahead of Rotorua's Ian Wood and Darrel Manson, both driving Mazda RX7s.
Motorsport BOP Mamaku Rallysprint: 1 Alex Kelsey (Subaru Impreza WRX) 8m 23.43s; 2 Ben Thomasen (Subaru Impreza WRX) 8m 36.07s; 3 Mitch James (Toyota Starlet) 9m 16.73s; 4 Ian Wood (Mazda RX7) 9m 26.74s; 5 Darrel Manson (Mazda RX7) 9m 36.36s; 6 Shannon Chambers (Mitsubishi Lancer EvoX) 9m 37.25s; 7 Shane Wright (Nissan Skyline) 9m 39.27s; 8 Kevin Bennett (Toyota Celica GT4) 9m 42.98s; 9 Anthony Jones (Ford Escort) 9m 44.59s; 10 McRae Sloper (Honda Civic) 9m 46.92s.