1994 MAZDA MX-5 Workshop Manual

B DISASSEMBLY CYLINDER BLOCK (INTERNAL PARTS) Disassemble in the order shown in the figure, referring to Disassembly Note. 1. Connecting rod cap Inspection ................. page B-45 2. Lower connecting rod bearing Inspection ................. page 8-45 3. Connecting rod and piston assembly Disassembly Note .......... page 545 4. Upper connecting rod bearing Inspection ................. page 8-57 5. Piston ring Disassembly Note .......... page 545 Inspection ................. page 555 6. Piston pin clip 7. Piston pin Disassembly Note Inspection ................. page 6-45 8. Piston Inspection ................. page 555 9. Connecting rod Inspection ................. page I345 10. Main bearing cap Disassembly Note .......... page 8-46 11. Lower main bearing Inspection ................. page B-46 12. Crankshaft Inspection ................. page 8-46 13. Upper main bearing Inspection ................. page 8-46 14. Thrust bearing Inspection ................. page 6-63 15. Oil jet Inspection ................. page B-53 16. Cylinder block Inspection ................. page 553 Gartner Banana

DISASSEMBLY Disassembly Note Connecting rod cap Before removing the connecting rod caps, measure the connecting rod side clearance. (Refer to page 8-64.) Connecting rod and piston assembly 1. Before removing the connecting rod and piston assem- bly, measure the connecting rod oil clearance. (Refer to page 8-64.) 2. Remove the Plastigage from the crankpin journals. 3. Use the handle of a hammer to remove the piston and connecting rod assembly through the top of the cylinder block. Piston ring Remove the piston rings with a piston ring expander (commercially available). Piston pin Remove the piston pin with the SST. Gartner Banana

DISASSEMBLY Main bearing cap 1. Before removing the main bearing caps, measure the crankshaft end play. (Refer to page B-64.) u 2. Loosen the main bearing cap bolts in two or three steps in the order shown in the figure. 3. Remove the main bearing caps. Crankshaft Before removing the crankshaft, measure the main bearing oil clearances. (Refer to page B-62.) Gartner Banana

INSPECTION I REPAIR INSPECTION 1 REPAIR PREPARATION SST 49 801 2 005 Remover & installer, valve guide Nut (Part of 49 LO1 2 OAO) For removal of valve guide 49 LO1 2 002 Body (Part of 49 LO 1 2 OAO) For installation of valve guide For installation of valve guide 49 LO1 2 OAO Installer set, 4 8 valve seal & valve guide t~@ Installer (Part of 49 LO1 2 OAO) For installation of valve guide For installation of valve guide 1. Clean all parts, being sure to remove all gasket fragments, dirt, oil or grease, carbon, moisture residue, and other foreign materials. 2. Inspection and repairs must be performed in the order specified. L 45UOBX485 CYLINDER HEAD 1. lnspect the cylinder head for damage, cracks, and leak- age of water and oil. Replace the cylinder head if neces- sary. 2. Measure the cylinder head distortion in the six directions shown in the figure. Distortion: 0.lOmm (0.004 in} max. 3. lnspect the following and repair or replace the cylinder head as necessary. (1) Sunken valve seats (2) Damaged intake and exhaust manifold contact sur- faces (3) Excessive camshaft oil clearances and end play 4. If the cylinder head distortion exceeds specification, grind the cylinder head surface. 5. If the cylinder head height is not within specification, re- place it. Height: 133.8-1 34.0mm (5.268-5.275 in) Grinding: O.lOmm (0.004 in} max. Gartner Banana

B INSPECTION / REPAIR 8' STEM TIP VALVE FACE MARGIN 1 ANGLE THICKNESST 450 6. Measure the manifold contact surface distortion in the four directions shown in the figure. Distortion: 0.15mm (0,006 in) max. u 7. If distortion exceeds specification, grind the surface or replace the cylinder head. Grinding: 0.20mm (0.008 in) max. VALVE MECHANISM Valve and Valve Guide 1. Inspect each valve for the following. Replace or resur- face the valve if necessary. (1) Damaged or bent stem (2) Rough or damaged face (3) Damaged or unevenly worn stem tip 2. Measure the valve head margin thickness of each valve. Replace the valve if necessary. Margin thickness IN: 0.9mm (0.035 in) EX: 1 .Omm (0.039 in) 3. Measure the length of each valve. Length Standard IN: lOl.89mm (4.0114 in) EX: 101.99mm (4.01 53 in) Minimum IN: 100.39mm (3.9524 in) EX: 100.49mm (3.9563 in) 4. Measure the stem diameter of each valve at the points shown. Diameter IN: 5.970-5.985mm (0.23514.2356 in) EX: 5.965-5.980mm (0,23494.2354 in) Minimum IN: 5.920mm (0.2331 in) EX: 5.9515mm (0.2329 in) 5. Measure the inner diameter of each valve guide at the points shown. Inner diameter IN: 5.99-6.03mm (0.2359-0.2374 in) EX: 5.99--6.03mm (0.23594.2374 in} 6. Calculate the valve stem-to-guide clearance. Subtract the outer diameter of the valve stem from the inner diameter of the corresponding valve guide. Clearance IN: 0.005-0.060mm (0.00024.0023 in) EX: 0.01 O-O.065mm (0.0004--0.0025 in) Maximum: 0.20mm (0.008 in) Gartner Banana

INSPECTION I REPAIR B WITH CARBON EX CUTTER 7. If the clearance exceeds specification, replace the valve and/or valve guide. 8. Measure height A of each valve guide. Replace the valve guide if necessary. Height: 18.3-18.9mm (0.7214.744 in) Replacement of valve guide Although the intake and exhaust valve guides are differ- ent, use the exhaust valve guide to replace the intake valve guide. Removal Remove the valve guide from the side opposite the com- bustion chamber with the SST. Installation 1. Assemble the SST so that depth L is as specified. Depth L: 18.3-18.9mm (0.7214.744 in) 2. Tighten the nut. 3. Tap the valve guide in from the side opposite the com- bustion chamber until the SST contacts the cylinder head. 4. Verify that the valve guide height is within specification. Height: 18.3-18.9mm (0.721-4.744 in) 5. If not, repeat steps 14. Gartner Banana

INSPECTION 1 REPAIR Valve Seat 1. lnspect the contact surface of each valve seat and valve face for the following: (1) Roughness u (2) Damage 2. If necessary, resurface the valve seat with a 45" valve seat cutter andlor resurface the valve face. 3. Apply a thin coat of Prussian blue to the valve face. 4. lnspect the valve seating by pressing the valve against the seat. (1) If blue does not appear 360" around the valve face, replace the valve. (2) If blue does not appear 360" around the valve seat, resurface the seat. 5. Measure the seat contact width. Width: 0.8-1.4mm (0.032-4.055 in) 6. Verify that the valve seating position is at the center of the valve face. (1) If the seating position is too high, correct the valve seat with a 70" cutter and a 45" cutter. (2) If the seating position is too low, correct the valve seat with a 0° cutter and a 45" cutter. 7. Seat the valve to the valve seat with lapping compound. 8. lnspect the sinking of the valve seat. Gartner Banana

INSPECTION / REPAIR OUT-OF-SQUARE I 9. Measure the valve stem protruding length (dimension L). Dimension L: 45.0mm (1.772 in) (1) If L is 45.0-E.5mm (l.772-l.79l in), no correc- tion is needed. (2) If L is 45.5-46.5mm (1.792-1.830 in), adjust with washer on spring seat area of cylinder head. (3) If L is 46.5mm (1.831 in) or more, replace cylinder head. Valve Spring 1. lnspect each valve spring for cracks or damage. 2. Measure the free length and out-of-square. Replace the valve spring if necessary. Free length Standard: 46.26mm (1.821 in) Minimum length: 39.5mm (1.56 in) with a set load of 224--253 N (22.G25.8 kgf, 50.2-56.7 Ibf) Out-of-square: 1.62mm (0.0638 in) max. CAMSHAFT 1. Set the front and rear journals on V-blocks. 2. Measure the camshaft runout. Replace the camshaft if necessary. Runout: 0.03mm (0.0012 in) max. 3. lnspect the camshaft for wear or damage. Replace the camshaft if necessary. 4. Measure the cam lobe heights at the two points as shown. Height Standard IN: 44.094mm (1,7360 in) EX: 44.600mm (1.7560 in) Minimum IN: 43.894mm (1,7281 in) EX: 44.400mm (1.7480 in) Gartner Banana