TIAGO BSVI MCE - SERVICE MANUAL

1.2L REVOTRON ENGINE 56 D. Valves : DANGER  Petrol and Petrol fumes are extremely explosive!! Use caution when working with gasoline, otherwise explosion or fire may occur, causing severe burns or death. 1. Check for leakage past the valves and valve seats by placing the intake and exhaust valves in the cylinder head and pouring gasoline or isopropyl alcohol in the valve chamber. Leakage indicates damaged valve seats and/or valves. Note the location of each valve so the valve can be matched to the same location during reassembly. 2. Inspect each valve for damage. Do not attempt to repair damaged valves. Replace valves exhibiting the conditions in the following list.  Burnt head or excessive carbon deposits.  Scoring or scratches on the valve surface  Excessive wear  Bend 3. Check for bent valves and excessive runout between valve seat and stem by placing the valve in a measuring fixture. 4. Place a dial indicator on the valve head and valve stem and rotate the valve, observing movement on both dial indicators. 5. The maximum permissible runout for both exhaust and intake valve is 0.030 mm. 6. Measure the other valve dimensions listed in table. NOTE  Remove the valve from the grinding machine and check valve head thickness. The minimum valve head thickness of the valve is 0.85 mm. 7. Rotate the valve under axial pressure several times and remove from the cylinder head. 8. Inspect the area of contact created by the axial rotation of the valve.  The contact pattern should be equal and unbroken around the circumference of the seat.  The distance from the narrow diameter of the valve seat face to the contact line should be 0.5 mm.