Old Bike Australasia – July 21, 2019

OLD BIKE AUSTRALASIA: 27

HONDA RC70F

upgrade due to higher compression pistons and more
aggressive camshaft timing. One of the RC70s was
assigned to budding scrambles rider Preston Petty,
who later founded the plastic mudguard revolution
that found a ready market in the booming off-road
scene. Petty won several local Southern California
dirt races on the RC70F, which later had a CE71
engine fitted. As the Honda was developed, some
reports say Petty trimmed off the factory-installed
leading-link suspension front end and machined up
a new steering head which could hold AJS telescopic
front forks and a wider, smaller 18 inch front wheel
in place of the standard 2.75 x 19 front tyre.
The RC70F varied slightly in specification during
the period of its catalogued existence, some being
fitted with a high level exhaust pipe with a
substantial muffler on the right hand side, others
with straight through pipes exiting in front of the
right hand rear shock absorber, and others with
low road-style pipes and muffler. There were
also dry-sump versions available.
The 1960-61 pre-production Honda 250
Scrambler prototypes also came with
single-carb Dream engines, but with
return shift transmissions. When the
1961 CB72 Hawk sport bikes were
released, the first thing that

happened to the “next generation” 250 Scrambler

was again a motor transplant, but this time from a

CB72, which had dual carbs, even higher

compression pistons and a 10,000 rpm redline.

In fairness to Honda, they were not the only ones

who offered “rotary gearboxes” to the public. Early

Yamahas, the Bridgestone 175s and Lilac motorcy-

cles also had this feature for a few years, among

other now-extinct manufactured models. Honda

continued to offer the rotary-gearbox option on

domestic 250-305cc Dreams and CYP77 Police bikes

into the mid-1960s, but no other “large” models

were so equipped after that.

Resurrecting an RC70F

The subject of this remarkable restoration was

discovered in Spain. Although it is thought

to possibly be the ex-Preston Petty

bike, this may not be the case given

the substantial modifications Petty

was said to have carried out, because this

one, as found, was in basically standard condition.

It had been ridden to near destruction, with oil

baked on everything and many parts missing or

semi-destroyed. However it was the chance to give

a new life to a very rare motorcycle – Honda’s first

production motocrosser – and the RC70 was soon

on its way to its new owner, Mike Buttinger

(founder of Consolidated Motor Spares, or CMS,

the world’s largest independent supplier of parts

for Japanese bikes) in Holland.

It arrived mid-2014 and once ensconced in The

Netherlands, the RC70 was entrusted to Marnix

Deibert and Sebas van de Broek, who have done

many restorations for CMS, including the C71Z

featured in OBA 76. It turned out to be a big job.

ABOVE The featured RC70 as found in Spain. TOP RIGHT Preston

Petty’s RC70F in 1959. RIGHT Preston Petty on his RC70 at a

scrambles event at Hopetown, California in 1960.