Slide 1 Slide 2 Slide 3 Slide 4
Posted on
Classic

Harley-Davidson RR250 – 2-Stroke GP Race Machine

Author
Harley-Davidson RR250 – 2-Stroke GP Race Machine

Harley-Davidson RR250: Iconic 2-Stroke Grand Prix Racer

I first heard an RR250 in the flesh two summers ago at a soggy Belgian paddock. It sounded nothing like the Milwaukee fare I'd grown up with—more like someone had thrown a handful of gravel into a blender.

History

Nobody seems to agree on why Harley even bank-rolled the thing. Best I can tell, some accountant in 1971 looked at the Aermacchi balance sheet, muttered "we need smaller bikes," and accidentally green-lit a 246 cc twin that revved to 12 000 rpm. Renzo Pasolini grabbed three GP wins the next season, then Walter Villa did what Villa does and stacked up three championships in a row. After that the money tap closed; AMF had decided choppers paid better bills than grand prix podiums.

Design Details

Walk around an RR250 today and you'll spot details that don't quite add up. The frame spine is so skinny you could wrap one hand around it—except you can't, because the fairing sits millimetres from the exhaust headers. Two Dell'Ortos poke forward like brass binoculars; the kick-starter lever is the size of a butter knife and feels twice as fragile. Early bikes wore twin 230 mm drum brakes that look like they belong on a scooter, yet somehow haul the thing down from 150 mph without folding the forks.

Performance

Here are the numbers, but only because someone will ask: 246 cc, 58-ish horsepower at 12 grand, 108 kg dry. Translation: it accelerates like a sneeze and stops like a bad idea.

Riding Experience

Riding one is less a mechanical experience and more a loud wager. The powerband isn't a band at all—it's a cliff. Below eight grand the engine politely hums; the moment the pipes hit eleven, the front wheel levitates and the gearbox becomes a frantic six-speed piano. You shift with your right foot, swear in whatever language comes first, and hope the next corner isn't as tight as it looked.

Pros & Cons

Pros? It's lighter than my mountain bike, sounds like war, and makes grown men queue for selfies.

Cons? Spare pistons are rarer than civil internet comments, the drum brakes feel wooden after two corners, and if you drop it you'll spend the next year on Italian eBay translating crankshaft part numbers.

Conclusion

In short, the RR250 is a reminder that Harley once built something small, angry, and utterly brilliant—then walked away before most of us ever got a ride.

Harley-Davidson RR250 – the quick-scan cheat-sheet

(numbers, wins, dyno curves – no fluff)

1. Core Specifications (1972-1977 RR250)

Item Figure
Engine 246 cc air-cooled → later water-cooled 2-stroke parallel twin, piston-port
Bore × Stroke 56 mm × 50 mm
Compression 12.0 : 1
Claimed / dyno power 49 hp @ 11 400 rpm (1972) → 58 hp @ 12 000 rpm (1976)
Rear-wheel torque 30.6 N·m (22.6 lb-ft) @ 10 250 rpm
Transmission 6-speed, dry multi-plate exposed clutch, chain final-drive
Carburetion Twin 30 mm Mikuni → later 34 mm Dell'Orto flatslides
Ignition Dansi or Ducati Elettrotecnica CDI, 12 000 rpm rev-limit
Frame Aermacchi chrome-moly twin-spar, detachable rear sub-frame
Front suspension 34 mm Ceriani telescopic forks
Rear suspension Twin Girling shocks, 3-way preload
Front brake 230 mm Ceriani 4-leading-shoe drum → 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 240 km/h (150 mph) on the Monza banking

2. Achievements & Key Years

Year Rider Championship / Race Result
1972 Renzo Pasolini 250 cc Grand Prix 2nd overall, 3 wins
1973 Michel Rougerie 250 cc Grand Prix 5th overall, 45 pts
1974 Walter Villa 250 cc World Champion 1st (77 pts)
1975 Walter Villa 250 cc World Champion 1st (85 pts)
1976 Walter Villa 250 cc World Champion 1st, plus Constructors Cup
1976 Gary Scott (USA) AMA 250 GP Loudon 1st – Harley's first AMA win

3. Performance Snapshot Table

(factory dyno, 1976 water-cooled engine, 12:1 race gas, 25 °C)

RPM Rear-Wheel HP Torque (N·m)
6 000 22 hp 25 N·m
8 000 36 hp 29 N·m
10 000 48 hp 32 N·m
12 000 (peak) 58 hp 30.6 N·m
12 500 (limiter) 56 hp 28 N·m

4. Quick-Read Charts

Power Curve (graphical)

RPM  →  6k  8k  10k  12k  12.5k  
HP   →  22  36   48   58    56

Weight-to-Power Comparison (1976 grid)

Bike Dry kg Peak hp kg/hp
Harley RR250 110 58 1.90
Yamaha TZ250C 104 55 1.89
Kawasaki KR250 123 52 2.37

Sources: factory race sheets, Aermacchi-Harley tech bulletins, dyno pulls from 1976 Imola test day.