Craftsman Motorcycle Vehicles Maintenance cheat sheet

Four-stroke cycle order: intake, compression, power, exhaust - one power stroke per two crankshaft revolutions per cylinder.

Compression test: throttle wide open, engine warm, all plugs removed; healthy readings typically 120–180 psi (8–12 bar) with less than 10% variation between cylinders.

Leak-down test thresholds: under 10% leakage is good; 10–20% marginal; over 20% indicates worn rings, burned valves, or head gasket failure.

Leak-down diagnosis by listening: air at the exhaust port = exhaust valve; at the intake/carburetor = intake valve; at the crankcase breather = rings or piston; at the radiator = head gasket.

Valve clearance is checked at the specified engine temperature (usually cold) and set with a feeler gauge; tight exhaust clearances cause hard hot starting and burned valves.

Oil smoke signals: blue smoke at startup = valve guides/seals; blue smoke under load = rings or cylinder wear; white smoke = coolant ingress; black smoke = rich mixture.

Cylinder head torque is applied in a spiral sequence from center outward, in stages, to the manufacturer's final value; retorque only if the procedure specifies it.

Timing chain/belt wear shows as cam timing drift, rattle at idle, or a cam/crank sensor correlation fault; verify timing marks before disassembly.

Bottom-end knock that rises with load and disappears on deceleration points to rod bearings; a knock at idle only often indicates main bearings or piston slap.

Stoichiometric air-fuel ratio for gasoline is about 14.7:1 by mass; lambda 1.0 equals this ratio, and closed-loop EFI targets it under light load.

Fuel pressure diagnosis: measure static pressure, then running pressure, then pressure drop after key-off; a rapid drop indicates leaking injector or failed check valve.

Injector flow is rated in cc/min or lb/hr; a rough-running cylinder can be isolated with a cylinder balance or injector disable test.

Ignition coil primary resistance is typically 0.5–3 ohms and secondary 5–15 kilohms; open or shorted windings cause misfire under load.

Spark plug heat range: a hotter plug runs higher tip temperature; a colder plug resists pre-ignition in high-load or high-compression engines.

Plug reading: tan/gray insulator = normal; black soot = rich or weak spark; white blistered = lean or overheating; oil-fouled = ring or guide wear.

Ignition timing advance is set with a strobe at the specified rpm with the timing connector grounded or the ECU in base-timing mode; base advance is typically 5–15° BTDC at idle.

Three-way catalyst efficiency is monitored by comparing upstream and downstream oxygen sensor signals; a downstream signal that mirrors the upstream indicates a failed cat.

EVAP system leaks are located with a smoke machine or pressure decay test; a purge valve stuck open causes rich running and rough idle after refueling.

Wet clutch free play at the lever is typically 10–20 mm; insufficient free play causes slippage, excessive free play causes drag and hard neutral finding.

Clutch slip test: apply full torque in a tall gear at low speed; engine rpm rising faster than road speed confirms slip from worn plates, weak springs, or contaminated oil.

Clutch drag symptoms: creeping with the lever pulled, difficult neutral at standstill, and hard shifting; causes include warped plates, air in the hydraulic line, or overfilled oil.

Chain slack is measured at the midpoint between sprockets with the bike on its wheels; typical spec is 20–35 mm, and adjustment is made at the rear axle with alignment confirmed.

Chain wear limit is reached when 20 links measure beyond the manufacturer's specified length (often 1–2% stretch); replace chain and sprockets as a set.

Sprocket wear signs: hooked or pointed teeth, and a chain that lifts more than half a tooth height off the rear sprocket at the 3 o'clock position.

Shaft drive final gear oil is changed at the specified interval (commonly 10,000–24,000 km) and checked at the filler plug level; hypoid gear oil grades per manual.

Belt drive tension is set by deflection under a specified force, and misalignment causes edge wear and chirping; never twist or kink a belt during installation.

Hydraulic brake fluid is hygroscopic; DOT 4 absorbs moisture and should be flushed at intervals of about 2 years or per the manufacturer's schedule.

DOT 3, DOT 4, and DOT 5.1 are glycol-based and miscible; DOT 5 is silicone-based and must never be mixed with glycol fluid.

Brake fluid boiling point drops as water content rises; wet boiling point for DOT 4 is about 155 °C versus roughly 230 °C dry.

Lever feel diagnosis: a spongy lever indicates air in the system; a lever that sinks under constant pressure indicates an internal master cylinder seal failure.

Brake pad minimum thickness is typically 1 mm of friction material above the backing plate; replace pads as a set per caliper or axle.

Brake disc minimum thickness is stamped on the disc hub; measure with a micrometer at several points and replace if below spec or if runout exceeds about 0.1 mm.

Bleeding sequence starts at the caliper farthest from the master cylinder and follows the manufacturer's order; keep the reservoir above the minimum mark throughout.

ABS faults: a wheel speed sensor air gap or damaged tone ring causes a fault code and ABS disable; the base brakes remain functional but without modulation.

Brake drag is diagnosed by riding briefly without using brakes and checking disc temperature; a hot disc points to a sticking caliper piston or clogged return port.

Fork sag is set with rider and gear aboard: total sag is typically 25–35 mm for street use and is adjusted with preload spacers or adjusters.

Rebound damping that is too fast causes a pogo effect after bumps; too slow causes packing down over repeated bumps.

Compression damping affects bump absorption; too stiff causes harshness and deflection, too soft causes bottoming under braking or in dips.

Fork oil level is measured from the top of the tube with the fork fully compressed and the spring removed; level changes air-spring effect more than damping.

Steering head bearing play is checked by lifting the front wheel and feeling for fore-aft rock at the fork legs; overtightening causes weave and notchy steering.

Wheel alignment on a motorcycle is confirmed by the string-line method or a straightedge along the rear wheel; rear axle misalignment causes accelerated tire wear and offset handling.

Static and dynamic wheel balance: static imbalance shows as hopping at low speed; dynamic imbalance shows as vibration at higher speed and requires spin balancing.

Tire pressures are set cold; a 10% rise after a ride is normal, while a larger rise indicates underinflation or excessive load.

Wheel runout limits are typically about 0.5 mm radial and 0.8 mm axial for cast wheels; spoke wheels require truing when runout exceeds spec.

Ohm's law: V = I × R; power P = V × I. A 12 V circuit drawing 5 A dissipates 60 W and has 2.4 ohms resistance.

Battery state of charge from open-circuit voltage: 12.6 V ≈ 100%, 12.4 V ≈ 75%, 12.2 V ≈ 50%, 12.0 V ≈ 25%; measure after a rest period.

Charging system test: at 2,000–3,000 rpm the battery should read about 13.5–14.8 V; lower indicates a weak stator, regulator, or connection.

Stator test: measure resistance between phases (typically 0.2–1.0 ohm) and check for continuity to ground; any ground continuity indicates a shorted winding.

Regulator/rectifier failure modes: overcharging boils the battery and blows bulbs; undercharging leaves the battery flat after a short ride.

Parasitic draw is measured with an ammeter in series at the negative terminal; typical acceptable draw is under 30 mA with the key off.

Voltage drop testing: place the meter across the circuit under load; more than 0.5 V drop on a 12 V circuit indicates excessive resistance in a cable or connector.

CAN bus diagnosis requires about 60 ohms between CAN high and CAN low with the bus asleep; 120 ohms indicates one terminator is missing.

ECU fault codes are read with a scan tool or blink code; always record freeze-frame data before clearing codes.

Frame crack inspection focuses on welds near the steering head, swingarm pivot, and engine mounts; dye penetrant or magnetic particle methods reveal fine cracks.

Steering head bearing notchiness is felt by raising the front end and sweeping the bars lock to lock; a detent at center indicates brinelling.

Swingarm pivot play is checked with the rear wheel off the ground by rocking the swingarm side to side; any movement indicates worn bushings or bearings.

Fork tube inspection: pitting or scoring on the chrome in the seal travel area causes leaks; check for bends with a straightedge or V-blocks.

Wheel bearing play is checked by grabbing the tire at 12 and 6 o'clock and rocking; movement without corresponding fork or swingarm movement indicates a bad bearing.

Body panel fasteners and rubber grommets isolate vibration; missing grommets cause panel cracks and rattles that mimic mechanical faults.

Fairing bracket alignment affects headlight aim and handlebar clearance; check for bent stays after any tip-over.

Corrosion inspection points: battery box, under the seat, inside the swingarm, and around the steering head; galvanic corrosion weakens fasteners and grounds.

Luggage and accessory mounting must not load the frame beyond the manufacturer's stated maximum; overload causes subframe cracking.

Engine oil change interval is set by distance and time, whichever comes first; oil degrades with heat cycles even when mileage is low.

Oil viscosity grade follows the manual, for example 10W-40; the first number is cold-flow behavior and the second is viscosity at operating temperature.

JASO MA/MA2 oil is specified for wet clutches; automotive energy-conserving oils contain friction modifiers that cause clutch slip.

Oil level is checked with the bike upright on level ground, engine warm, after the specified wait; overfilling causes foaming and seal leaks.

Air filter restriction reduces power and enriches the mixture on carbureted engines; clean or replace at the interval or sooner in dusty conditions.

Tune-up checklist: spark plugs, air filter, valve clearance, throttle and clutch cable free play, chain tension and lubrication, tire pressures, and fastener torque.

Torque values are applied to clean, dry threads unless the manual specifies lubrication; lubricated threads overstress fasteners at the same wrench setting.

Fastener inspection after service covers axle nuts, caliper bolts, and handlebar clamps; use a torque wrench and mark critical fasteners.

Pre-ride inspection items: tires and pressures, controls, lights and horn, fluid levels, chain or belt condition, and mirrors.