* Crutchlow first Briton to lead top flight since Sheene in 1979
* Marquez and Rossi collide, both out of the points
* Crutchlow now three points clear of Dovizioso
* Zarco finishes second, Rins third (Adds quotes, details)
April 8 (Reuters) - Cal Crutchlow won a damp and chaotic Argentine MotoGP race on Sunday to became the first Briton to lead the top category of grand prix motorcycling since the late Barry Sheene nearly 40 years ago.
The non-works LCR Honda rider, celebrating a third career MotoGP win and Honda’s 750th grand prix success, now has 38 points and leads Ducati’s Italian Andrea Dovizioso by three after two races.
Sheene, a double world champion for Suzuki in the old 500cc era, last led the standings in 1979.
“It was nice to win, but it was to be expected to be honest,” said Crutchlow.
“I was comfortable in the battle, I felt I took no risks. I stayed with riders I probably should have and would have been able to drop if I needed to.
“I think we could have fought no matter which circuit it would have been this weekend.”
Frenchman Johann Zarco finished a close second for Tech3 Yamaha after a last lap battle for the lead while Honda’s reigning world champion Marc Marquez was penalised for a collision with Yamaha’s Italian great Valentino Rossi.
Spaniard Alex Rins was third for Suzuki, his first MotoGP podium, at the Termas de Rio Hondo circuit.
The race start was delayed for safety reasons amid farcical scenes, with rain before the event leaving all riders except Australian pole sitter Jack Miller on wet weather tyres. The fast-improving conditions then triggered a mass return to the pits for a change of tyres with only Miller’s Pramac Ducati remaining on the grid.
Organisers decided, after consultations with team bosses in order to avoid a mass start from the pits, to leave Miller alone out front and several rows clear of the others after grid penalties.
Marquez then stalled, the four-times MotoGP champion wheeling the bike clear, bump-starting it and then riding the wrong way down the track to resume his starting position against the rules.
Marquez quickly reeled the Australian in and passed him before receiving a ride-through penalty for the start infringement, knocking him back to 19th.
Miller, Rins, Zarco and Crutchlow broke clear with all four leading in turn while Marquez and Rossi tangled with four laps to go.
The Spaniard was handed a 30 second penalty, dropping him down to 18th with Rossi, who went off track and fell following the collision before resuming, in 19th.
The next race is in Texas, at the Circuit of the Americas in Austin, on April 22. (Reporting by Alan Baldwin in London, editing by Pritha Sarkar)