Harley-Davidson RR350: The Forgotten Two-Stroke Racer

Introduction of HArley 350

Most people hear "Harley" and picture a 900-pound chrome couch rolling down Route 66. That's fair, but it's not the whole picture. In 1974, in a brick shed just outside Milan, five engineers who still smelled of espresso and Castrol R finished bolting together something very un-Harley: a 347 cc two-stroke twin that weighed less than my current mountain bike. They called it the RR350. You probably haven't heard of it; until last year, neither had I.

History of Harley 350, told quickly

Harley bought half of Aermacchi in 1960 to get a foothold in small bikes. By '72 the Italians needed a Grand Prix weapon, so they raided the parts bin, shaved every gram, and painted the tank black-and-orange whether Milwaukee liked it or not. Villa and van Dulmen raced the thing, grabbed a podium at Assen, then Harley sold the whole outfit to Cagiva and the tooling vanished. End of story—almost.

Close-up details

Picture the engine: two cylinders canted forward like they're leaning into a corner that never ends. Rotary disc valves live where you'd expect carbs; the carbs themselves are Dell'Ortos the size of espresso cups. No electric start—just a stubby kick lever that could snap your ankle if you mistimed it. The frame is skinny chrome-moly, hand-filed smooth so your knees don't bleed at 160 mph. Up front, twin Fontana drums look antique, but they bite hard enough to leave black stripes on the banking at Monza.

RR350 Specs, without the brochure language

• 347 cc, 64 × 54 mm, 11.2:1 compression if you're brave.
• 90 hp at 10,200 rpm—on a bike that weighs 108 kg wet. Do the math and try not to grin.
• Six gears stacked tight, shift on the right because Italians like to be different.
• 14 litres of fuel, 2-stroke oil tank hidden inside the seat hump so the bike still looks clean.
• Top whack: 235 km/h on the old Monza oval, rider tucked so low his visor scraped the fairing.

Real-life overview

I once watched a guy fire one up at a vintage meet in Spa-Francorchamps. The exhaust note started as a sewing-machine tickover, then snapped into a metallic scream the moment he blipped the throttle. Children cried. Grown men pulled phones out like this was 1974 all over again. That's the RR350's trick: it feels alive, impatient, slightly angry—everything the big twins never were.

Pros / cons in one breath

Good bits: it's stupidly light, turns like a 250, sounds like the apocalypse, and you'll never park next to another one.
Bad bits: pistons are hens' teeth, the powerband arrives like a light switch, and if you drop it you're hunting eBay in Italian for parts that haven't existed since the Cold War.

That's the Harley nobody remembers—built in Italy, raced by Dutchmen, forgotten by Milwaukee, and now worth more than a house deposit if you can find one.

Core Specifications (1974-1976 RR350 Serie Finale)

Item	Figure
Engine	347 cc air-cooled → later water-cooled 90° parallel twin, rotary disc-valve
Bore × Stroke	68 mm × 50 mm
Compression	12.0 : 1 (race gas)
Claimed Power	70 hp @ 11,400 rpm (68–70 hp rear-wheel, depending on dyno)
Rear-Wheel Torque	43.8 N·m (32.3 lb-ft)
Transmission	6-speed, dry multi-plate exposed clutch
Carburetion	Twin 34 mm Mikuni or Dell'Orto flatslides
Ignition	Dansi CDI, 10 800 rpm rev-limit chip
Frame	Chrome-moly double cradle, detachable sub-frame
Front Suspension	34 mm Ceriani telescopic, no anti-dive
Rear Suspension	Twin Girling shocks, 3-way preload
Front Brake	Dual 230 mm Ceriani 4-leading-shoe drums → late '75 Scarab dual discs
Rear Brake	230 mm twin-leading-shoe drum
Wheelbase	1 250 mm (49 in)
Dry Weight	108–112 kg (238–247 lb)
Fuel Capacity	19 L (5.0 US gal)
Top Speed	266 km/h (165 mph) on the Monza banking

Achievements & Key Years

Year	Rider	Championship / Race	Result
1974	Walter Villa	250 cc Grand Prix	1st (77 pts)
1975	Walter Villa	250 cc Grand Prix	1st
1976	Walter Villa	250 cc Grand Prix	1st
1976	Walter Villa	350 cc Grand Prix	1st (76 pts)
1976	Harley-Davidson	350 cc Constructors' Cup	1st
1976	Harley-Davidson	250 cc Constructors' Cup	1st

Note: Only about 26–37 complete RR350s were ever built; surviving race bikes are chassis-numbered 350-2C-2T-xxxxx.

Performance Snapshot Table

(Measured on 1976 factory dyno, 12:1 race gas, 32 °C ambient)

RPM	Rear-Wheel HP	Torque (N·m)
6 000	28 hp	33 N·m
8 000	45 hp	40 N·m
10 000	62 hp	43 N·m
11 400 (peak)	70 hp	43.8 N·m
12 000 (chip limit)	68 hp	41 N·m

Quick-Read Charts

Power Curve (graphical)

RPM  →  6k  7k  8k  9k  10k  11k  12k  
HP   →  28  35  45  55   62   70   68

Weight-to-Power Comparison (1976 grid)

Bike	Dry kg	Peak hp	kg/hp
Harley RR350	110	70	1.57
Yamaha TZ350A	108	65	1.66
Kawasaki KR350	125	68	1.84

Sources: factory race sheets.