Yes, he knows smoking kills but he isn't bothered.
''A drunk driver already tried to do that and it didn't work,'' he said.
Even Kempster is amazed he survived the crash, which happened at dusk on a country road near Melbourne.
Others are amazed at what Kempster (51) has achieved since. He was a competitive water-skier for 10 years, claiming seven Australian and three world disabled titles before returning to his first love, motorcycle racing.
He races about a dozen times a year - calling himself Boneapart Racing and using the racing number . He is in Invercargill as guest of the Southland Motorcycle Club to compete in four of the five events at next week's Burt Munro Challenge.
''There are only five things I have to do with my left hand - operate the throttle and the clutch and the brake, steer it, and hang on,'' he says, demonstrating on his bike, which was flown over from Australia.
He usually wears a $50,000 computerised artificial leg but prefers to race without it, saying it would be a danger to other riders if he was in an accident and it detached.
But he admits it is scary being a 55kg double amputee controlling a 150kg motorcycle, particularly on right-hand corners.
''Because I have no right knee, I can't judge how close the bike is to the ground. It is very easy to slip off if you're not careful.''
That is why he is happy the 50-mile Burt Munro beach race on Invercargill's Oreti Beach is raced anticlockwise.
''There will be 100 left turns, and those are much better for me.''
Kempster will use his own bike for the hard-surface racing and a 250cc bike modified for him by Honda Southland for the beach race.
A spray-painter before 1990, Kempster worked as a tourist boat skipper for 10 years afterwards but is now a beneficiary living near the town of Aubrey in Victoria.
He says he still gets choked up when he remembers the incident which cost him an arm and a leg.
''All of a sudden, a one-tonne truck came over the brow of the hill on the wrong side of the road. If it had been a car it might have been all right, but the truck had a tray on the back and it caught me.
''My hand came off and went one way, my arm came off and went another, and my leg went somewhere else. The bike went another 100m with me still on it before it fell over.''
When the police arrived, they were perplexed about what had happened to him, Kempster says.
''They couldn't work out what was going on. It took them a while to find my limbs.''
An unfortunate couple found his hand, he says. They had heard the commotion and gone out on to their driveway with a torch to investigate.
''The wife thought she saw a possum on the driveway and shone the torch on to it. She fainted and he threw up.''
Kempster credits his survival to a motorist who stopped to help. Few people had cellphones in 1990, but the man was a television sports commentator who had a ''brick'' phone and immediately rang for an ambulance.
''They told him what to do. Basically, he held me in a big bear hug to hold everything together and did that for 20 minutes until the ambulance arrived. He kept slapping me around the head and keeping me alert. He saved my life.''
The driver who struck him was discovered nearby intoxicated and washing blood off his vehicle at a service station, Kempster says. He was charged with failing to stop after an accident, but for various reasons was never charged with drink-driving.
''He never, ever admitted he had hit me. Yeah, I'm still a little bit pissed off about that. But you can't dwell on it.''
Kempster was in hospital for only three weeks but spent many months in a rehabilitation facility.
About six months after the incident he decided he wanted to try riding a motorbike but the attempt was a failure because he stalled the bike and could not restart it.
He put motorcycling out of his mind until 2009, when he decided to enter a social race event.
''Within six laps I had my left knee on the ground and I thought 'I'm back'.''
Kempster says he does not set out to win races but to compete against himself.
He races for the same reason he gives talks about his life and visits sick and disabled children in hospital.
''I want to show disabled people that they can do anything they set their minds to ... I try and inspire them to get back into anything they enjoyed before, or try anything they might enjoy.''
