Introduced around 2002, the Dolmar PS-7900 was the largest and most powerful member of the PS-6400/PS-7300/PS-7900 professional family.
Its major selling point was that Dolmar fitted a 78.5 cc engine into the same 6.3 kg powerhead used by the smaller models. With 4.6 kW of power, it achieved an excellent power-to-weight ratio of just 1.37 kg/kW. The PS-7900 was primarily intended for professional felling and bucking of larger timber. Dolmar offered it with bars up to 70 cm (28 inches).
Other practical features included tool-assisted quick access to the air filter, side-mounted chain tensioning, a decompression valve on equipped versions and an integrated inertia-activated chain brake. The clutch and sprocket were positioned outside the brake mechanism, making chain installation and cleaning the clutch area easier.
| Specification | Dolmar PS-7900 |
|---|---|
| Manufacturer | DOLMAR GmbH |
| Country of manufacture | Germany |
| Type designation | Type 038 |
| Approximate introduction | 2002 |
| Intended use | Professional felling and bucking |
| Engine type | Single-cylinder, air-cooled, two-stroke |
| Displacement | 78.5 cc / 4.8 cu in |
| Bore | 52 mm / 2.05 in |
| Stroke | 37 mm / 1.46 in |
| Cylinder | Nikasil-coated |
| Piston | Lightweight, single-ring |
| Maximum power | 4.6 kW / 6.3 PS / approximately 6.2 hp at 9,500 rpm |
| Maximum torque | 5.2 Nm / 3.84 lb-ft at 7,000 rpm |
| Power-to-weight ratio | 1.37 kg/kW |
| Idle speed | 2,500 rpm |
| Clutch engagement speed | 3,200 rpm |
| Maximum speed with bar and chain | 13,500 rpm |
| Carburetor | Zama diaphragm carburetor |
| Ignition | Electronic ignition with speed limiter |
| Spark plug | NGK BPMR 7A or Bosch WSR 6F |
| Spark-plug gap | 0.5 mm / 0.020 in |
| Starting assistance | Decompression valve on equipped versions |
| Fuel mixture | Generally 50:1 with approved two-stroke oil |
| Fuel consumption at maximum load | 2.3 kg/h |
| Specific fuel consumption | 505 g/kWh |
| Fuel-tank capacity | 0.75 L / 25.36 US fl oz |
| Oil-tank capacity | 0.42 L / 14.20 US fl oz |
| Oil pump | Automatic, clutch-driven and adjustable |
| Clutch | Three-shoe centrifugal clutch |
| Sprocket | Seven-tooth rim sprocket |
| Chain pitch | 3/8 in |
| Chain gauge | .058 in / 1.5 mm |
| Standard chain | Dolmar 099 full-chisel |
| Maximum chain speed | 20.83 m/s / 68.3 ft/s |
| Approved bar lengths | 15, 18, 20, 24 and 28 in / 38, 45, 50, 60 and 70 cm |
| Weight | 6.3 kg / 13.9 lb |
| Weight definition | Empty powerhead without bar or chain |
| Air-filtration system | Dolmar AirMaster pre-cleaning system |
| Anti-vibration system | Dolmar D2M two-mass steel-spring system |
| Front-handle vibration | 6.6 m/s² |
| Rear-handle vibration | 4.5 m/s² |
| Sound-pressure level | 104.3 dB(A), European measurement |
| Sound-power level | 113.3 dB(A), European measurement |
| Chain brake | Manual and inertia-activated |
| Chain tensioning | Side-mounted |
| Other safety equipment | Throttle lockout, chain catcher and front and rear hand guards |
| Heated-handle version | PS-7900 H |
| Makita equivalents | DCS7900, DCS7901, DCS7900H and DCS7901H |
Most famously, 24 model PS-7900s were used for the Dolmette Drag Motorcycle.
The model was also sold in blue Makita form as the DCS7900/DCS7901 and related variants. Dolmar subsequently introduced the emissions-updated PS-7910, although the two models overlapped in some markets; the PS-7900 was still shown in at least one 2013 Dolmar catalogue.
