Rotax 655/95 Engine Repair Manual (OEM)

• Covers ROTAX engine type 655, with separate procedures for versions with and without a rev-counter drive; the rev-counter drive is identified as an ENDURO-only configuration.
• 1995 factory repair publication carrying BOMBARDIER-ROTAX GmbH and aprilia s.p.a. identification, 149 pages.
• Factory data for the 651.88 cc single-cylinder engine: 100 x 83 mm bore/stroke, 9.1:1 compression, 34 kW at 6,750 rpm, 56 Nm at 5,500 rpm, 1,400 rpm idle, and 7,500 rpm maximum admissible speed.
• Includes lubrication and cooling circuit diagrams, an ignition wiring diagram, gearbox and clutch exploded views, wear-limit tables, torque data, and fault-finding charts.
• Identifies dedicated ROTAX special tools by part number and gives measurement values for engine, gearbox, clutch, ignition, and lubrication-system repair.

Engine Architecture and Maintenance Overview

This factory repair manual gives a detailed structural breakdown of the ROTAX 655 engine. The dry-sump lubrication system uses two trochoidal pumps: a pressure/feed pump and a suction/return pump. Oil is divided into high- and low-pressure circuits; the low-pressure circuit lubricates and cools the gearbox, while the high-pressure circuit feeds the crankshaft main bearings, connecting-rod bearing, camshaft bearings, and the piston-cooling oil jet. The pressure-control circuit opens to the low-pressure side at about 3.5 bar.

Cooling is liquid-based, with a centrifugal water pump driven by the balance shaft. During warm-up, coolant bypasses the radiator; the thermostat begins opening at about 60°C. The technical table specifies a 50/50 antifreeze-water mixture. The drivetrain section identifies a multi-disc wet clutch, a 5-speed dog-engagement gearbox, a 72/37 primary ratio, and a 16-tooth chain sprocket final drive.

Variant notes matter on this engine. The oil-pump-drive section distinguishes engines with and without the rev-counter drive and records additional oil-pump-shaft circlips on engine Nos. 429 194-430 000 and generally from 430 696 onward. That serial break helps identify the correct internal arrangement before repair work starts.

The maintenance schedule calls for a first check at 1,000 km, engine-oil and filter service at 6,000 km intervals, valve-clearance and cam-chain checks at 6,000 km, spark-plug renewal at 12,000 km, and final-drive chain inspection/lubrication every 500 km. Water hoses have a replacement interval of 30,000 km or at least every three years.

Technical Specifications and Data

The reference tables define factory dimensions, clearances, wear limits, and tightening values for repair work. Camshaft timing is listed at 225° intake and 234° exhaust at 1 mm valve clearance. New piston-to-cylinder clearance is 0.016-0.034 mm, with a 0.090 mm wear limit, while crankshaft bearing radial clearance is limited to 0.1 mm.

Factory oil-pressure checks specify 1.5 bar at 1,200 ±100 rpm and 4 bar at 5,300 ±100 rpm, with the test performed at 30-40°C oil temperature. The ignition system uses a breakerless capacitor-discharge unit with electronically variable advance and a 3-phase AC generator rated at 12V/280W. Diagnostic tables provide resistance values for the generator, trigger sensor, ignition-coil primary and secondary windings, and spark-plug connector, plus an electronic-box test matrix for unit ND 071000-0790.

Torque data appears in dedicated tables and inside the assembly procedures. Examples include 48 Nm for the M10 cylinder-head collar nuts, 140 Nm for the clutch-hub retaining nut, and 180 Nm for the ignition/flywheel retaining nut. Several assemblies depend on controlled clamping, bearing preload, or indexed positioning rather than simple tightening.

Factory Repair Procedures and Diagnostic Depth

The manual names and illustrates workshop-level procedures that go well beyond routine maintenance:

• Engine removal, mounting on the dedicated trestle, full engine disassembly, crankcase separation, and reassembly.
• Crankshaft and balance-shaft removal, bearing service, axial-clearance shimming, gearbox disassembly/reassembly, gearshift-mechanism checks, and clutch overhaul.
• Cylinder, piston, cylinder-head, valve-guide, valve-seat, camshaft, rocker-arm, decompressor, cam-chain, oil-pump, water-pump, thermostat, starter-drive, and sprag-clutch repair.
• Valve-clearance adjustment, camshaft-drive timing, oil-pressure testing, ignition-system troubleshooting, stator/trigger checks, and symptom-based fault diagnosis.
• Special tools identified by factory part number, including the 277 919 engine trestle, 240 880 TDC locking bolt, 277 881 clutch-hub locking tool, 277 270 balance-drive locking pin, 276 357 piston-ring clamp, and 277 292 gearbox snap-ring pliers.

Representative drawings include the Lubrication System, Cooling Circuit, Ignition Unit — Wiring Diagram, Gearbox — Disassembly, Primary Drive and Clutch, and Camshaft Drive adjustment views. The PDF shows where measurement, timing, shimming, electrical testing, and special tooling enter the repair.

Several warnings address real assembly damage risks. When splitting the crankcase, the manual warns against forcing the halves apart or striking the sealing surfaces. During clutch work, the locking fixture must be fully seated so the clutch basket is not damaged while the retaining nut is loosened. On crankshaft/balance-shaft setup, insufficient balance-shaft axial play can overheat the ball bearings and lead to failure.

This is an engine-level repair manual, not a complete motorcycle chassis manual. Engine-oil and coolant fill quantities are referenced to the motorcycle manufacturer’s specifications, and motorcycle-level engine removal/installation remains tied to the manufacturer’s instructions. Ignition and flywheel work requires proper electrical isolation, and the engine must be securely supported for teardown.