Forklift Flywheel Ring Gear 490B-120C – Xinchai 490B

Forklift Flywheel Ring Gear 490B-120C — Xinchai 490B Diesel Engine Flywheel Ring Gear for Forklift Trucks

This forklift flywheel ring gear part number 490B-120C is a Kingstream OEM replacement ring gear for Xinchai 490B 4-cylinder diesel engines in 1-3.5 ton forklift trucks. The ring gear is precision-machined from hardened alloy steel, heat-treated for wear resistance at the tooth flanks where the starter motor pinion gear engages repeatedly during engine starting. The ring gear is heat-shrunk onto the flywheel — when heated, the ring expands sufficiently to slip over the flywheel, and upon cooling, contracts for a permanent interference fit that transmits cranking torque without slipping. 5kg with 100×100×40cm carton box packaging. 100% professional tested. 7-10 day delivery. Kingstream OEM quality for Xinchai 490B diesel forklift fleet operators.

INSTALLATION PROCEDURE: Step 1 — Remove the transmission and clutch to access the flywheel. Step 2 — Unbolt and remove the flywheel from the crankshaft. Step 3 — Support the flywheel on wooden blocks and drive the old ring gear off using a brass punch and hammer, striking evenly around the circumference. Step 4 — Clean the flywheel ring gear seat with a wire brush to remove rust and debris. Step 5 — Heat the new ring gear in an oven or with a torch to 200-250°C — the ring will expand by approximately 0.3-0.5mm. Step 6 — Using heat-resistant gloves, quickly position the heated ring gear onto the flywheel with the chamfered lead-in teeth facing the starter motor side. Step 7 — Allow the ring gear to air-cool to ambient temperature — do not quench with water as this can cause uneven contraction and cracking. Step 8 — Reinstall the flywheel onto the crankshaft using new bolts with thread locker, torquing in a cross-pattern sequence. Step 9 — Reinstall the clutch and transmission. Step 10 — Test engine starting and verify smooth, quiet starter engagement. 100% professional tested. Kingstream OEM.

SYMPTOMS OF RING GEAR FAILURE: Metallic grinding or screeching sound during engine cranking, starter motor spins but does not engage the engine, visible chipped or worn teeth when inspecting through the starter mounting hole, engine only cranks when the flywheel is in certain positions (ring gear has damaged sections), and starter pinion gear showing abnormal tooth wear from engaging a damaged ring gear. For Xinchai 490B diesel engine fleet flywheel maintenance, contact us. Kingstream OEM.

Technical Specifications

100% professional tested. Kingstream OEM. Contact us.