For quick troubleshooting, focus first on the air filter housing–remove the cover by releasing the two latches and inspect the foam element for debris. Replace if clogged or torn; clean with soapy water and dry completely before reinstalling. The carburetor sits beneath the filter compartment; detach the intake manifold by unscrewing the single retaining bolt to access it for adjustment or cleaning.
Next, locate the ignition module behind the flywheel. Remove the starter cover by undoing the three screws, then lift the flywheel using a puller tool (part #1123 020 1004) to expose the coil. Check the gap (.014–.018 inches) between the coil and flywheel magnets–misalignment causes hard starts. The fuel tank connects via a clear hose to the carburetor; trace it to its base near the throttle trigger if leaks appear.
To service the drive mechanism, flip the unit over and detach the six screws securing the housing cover. The impeller should spin freely without wobble; if damaged, order variant #4139 020 9601 (left-handed thread). Lubricate the shaft bearings annually with synthetic grease (NLGI grade 2). The muffler bolts to the exhaust port–remove it to clear carbon buildup, but note the gasket orientation to prevent exhaust leaks.
For electrical faults, test the stop switch continuity with a multimeter (should read 0 ohms when engaged, infinite when open). The trigger interlock requires simultaneous pressure–check the harness wires for fraying near the grip. Replace any burnt connectors with OEM pin terminals (#0000 802 3800).
Order replacements through authorized dealers only to avoid counterfeit parts–verify authenticity by cross-referencing the 10-digit serial number etched on the crankcase. Keep a torque wrench handy: fasteners require precise tightening (e.g., flywheel nut at 40 Nm).
Practical Guide to the BR 350 Blower’s Internal Layout
Always begin by locating the engine housing and fan impeller–these are the primary components requiring disassembly for most repairs. The impeller is secured with a reverse-threaded nut (left-hand thread, 17mm), which differs from standard fasteners. Use a strap wrench to grip the flywheel while applying counterclockwise force to the nut. Failure to recognize this threading can strip both the nut and fan shaft.
The fuel system’s carburetor and air filter assembly sit directly beneath the rear cover. Remove the three screws holding the cover (Torx T25) to access the filter. Replace the paper filter every 50 hours of operation, or sooner if debris accumulates. The carburetor’s adjustment screws (H, L, and idle) are preset from the factory–only alter them if performance declines after verifying fuel flow and spark integrity.
Key Components and Their Order of Disassembly
- Spark plug (14mm socket) – Inspect gap (.020 inches/.5mm) and electrode wear.
- Muffler and spark arrestor – Soak in degreaser if clogged; tap lightly to dislodge carbon buildup.
- Crankcase cover – Four bolts (8mm) hold the ignition module; avoid overtightening.
- Starter recoil – Pull cord slowly to release spring tension before removal.
The piston and cylinder are accessible after removing the crankcase cover, but honing the cylinder should only be attempted if scoring exceeds .002 inches. Use a bore gauge to measure wear–standard bore is 38.0mm. Piston rings (gap .008–.012 inches) must be aligned with the ring pegs during reassembly. Lubricate all moving parts with 2-stroke oil (50:1 ratio) before final assembly to prevent dry starts.
Throttle cable routing requires attention during reassembly. The cable must pass behind the choke lever and enter the carburetor housing without kinks. Misrouted cables cause erratic throttle response or sticking. Test the choke and throttle mechanisms after reassembly by operating the lever through its full range–no binding should occur.
- Verify gasket integrity–replace crankcase and cylinder head gaskets if brittle or torn. Silicone-based sealants can substitute temporarily but won’t endure heat cycles like OEM gaskets.
- Inspect the flywheel for magnet wear or cracks. A damaged flywheel disrupts ignition timing, leading to hard starts or misfires.
- Check the impeller’s balance. An unbalanced fan causes excessive vibration; static balance by removing material from heavy blades with a rotary tool.
Reassembly torque specs are critical. Cylinder head bolts: 18 Nm (13 ft-lb). Flywheel nut: 50 Nm (37 ft-lb). Loose fasteners risk component failure; over-tightening warps the crankcase. Store removed bolts and small components in labeled containers to avoid confusion during rebuild. A missing washer or misaligned gasket will leak air or compression.
Finding the Air Filtration Unit on the BR Engine Schematic
Start by identifying assembly reference number 26 in the exploded view–this denotes the complete intake housing. Directly adjacent, marked 27, is the snap-fit foam element you’ll need to service or replace. The filter sits upstream of the carburetor inlet, secured by a single latch on the right side of the housing; release it with a quarter-turn counterclockwise before lifting the cover.
Below is a quick-reference breakdown of the immediate components surrounding the air filtration section:
| Ref. No. | Component | Material | Removal Tool |
|---|---|---|---|
| 25 | Intake cover gasket | Silicone-coated paper | Plastic pry bar |
| 26 | Intake housing | Glass-filled nylon | T20 Torx |
| 27 | Foam pre-filter | Polyurethane | None |
| 28 | Mesh screen | Stainless steel | Small flathead |
Cleaning Procedure Without Disassembly
Compressed air at 40–60 psi directed through the intake grille on the left side will dislodge most debris from the foam without removing the cover. Keep the nozzle moving to avoid tearing the foam; rotate the engine once to ensure airflow reaches the entire filter surface. Inspect the mesh screen for embedded dirt–if visible clogs remain, proceed to full disassembly using the table above.
After reassembly, run the engine at idle for 30 seconds to verify unrestricted intake noise; a whistling or raspy tone signals incomplete sealing–re-check latch engagement and gasket alignment.
Step-by-Step Guide to Identifying the Carburetor Components
Locate the air filter housing first–it’s the rectangular or circular cover directly above the carburetor. Remove the housing screws with a T25 torx driver, then lift the cover to expose the filter element. The carburetor sits beneath, attached by two screws or clamps; detach these carefully to avoid damaging the gasket. Note the orientation of the throttle and choke levers–mark them with tape if unsure–before disconnecting the fuel line and linkage.
Disassembling the Carburetor
Separate the carburetor body from the intake by unscrewing the four corner bolts with a 5mm hex key. The main components to identify are the diaphragm, metering lever, needle valve, and idle adjustment screw. The diaphragm is a thin, flexible membrane on top of the fuel chamber–check for cracks or stiffness. The needle valve sits beneath the diaphragm, controlled by the metering lever; inspect for wear or corrosion. The idle screw is a brass-colored, finely threaded bolt on the side–do not force it beyond 1.5 turns from lightly seated.
Clean each component with carburetor cleaner, targeting the tiny jets in the body. The primary jet is the larger orifice near the fuel inlet, while the pilot jet is a smaller hole adjacent to the idle screw. Use compressed air to blow out debris, ensuring no blockages remain. Reassemble in reverse order, ensuring the diaphragm lays flat and the gasket seals properly–over-tightening the bolts can warp the housing. Before reinstalling, verify the needle valve moves freely by pressing the metering lever; resistance indicates misalignment or damage.
Step-by-Step Guide to Locating and Swapping the Ignition Coil with Schematic Reference
Disconnect the spark plug wire first to prevent accidental starts. Trace the high-voltage cable from the plug to the ignition module–it’s secured beneath the engine cover near the flywheel. Use a service manual’s exploded view to identify the coil’s position (marked as a rectangular housing with wiring terminals). If resistance tests show values above 10 kΩ or infinite readings, replacement is needed.
Removal Process
Remove the two screws holding the air filter housing–set aside without disconnecting hoses. The coil sits adjacent to the flywheel, typically fastened by two Torx T25 bolts or Phillips screws; use the correct driver to avoid stripping. Label wires before detaching connectors to ensure correct reassembly. Pry the coil gently with a plastic tool to avoid damaging surrounding components.
Inspect the flywheel magnets for debris or damage while the coil is removed. Clean the mounting surface with a lint-free cloth and brake cleaner–residue can disrupt signal transfer. Align the new module so its mounting holes match exactly; improper alignment causes misfires. Reconnect wires in the original configuration, ensuring connectors snap securely.
Verification and Testing
Reattach the spark plug wire and crank the engine briefly–listen for consistent firing. If sputtering persists, check the coil’s air gap (0.2–0.4 mm) using a feeler gauge between the flywheel magnets and module. Re-tighten fasteners to 6–8 Nm torque; overtightening risks thread damage. Reinstall the air filter housing, ensuring gaskets seal properly to prevent unmetered air entry.
Run the engine at idle for 30 seconds, then under load to confirm stable operation. If hesitation occurs, recheck connections and gap spacing. Store the old coil for emergency diagnostics; irregular resistance patterns often indicate deeper electrical issues requiring further troubleshooting.