OTTO Excavator Parts Ex400-5 6Rb1 Valve Spring Big 1125610636 112561-0636 1-12561063-6 For Isuzu OTTO Isuzu EX400-5 6RB1 Valve Spring Big 1125610636 – 100% genuine OEM excavator part, perfect fit for Isuzu 6RB1 engines. Bulk in-stock, fast global shipping. Superior elasticity & fatigue resistance vs aftermarket big springs, cuts rework & returns, boosts resale profits for wholesalers & agents.