Connecting Rods and Pistons/Pistons and Connecting Rods CTM2 (19APR90) 30-20 16, 18, 20 & 24HP Onan Engines AllTractorManuals.com 130495 21. Measure piston bore I.D. at four places; two measurements 90˚ apart at top of ring travel and two measurements 90˚ apart at bottom of ring travel. NOTE: If engine has had a previous major overhaul, oversize pistons and rings may have been installed. 22. Measure piston clearance (piston bore I.D. minus piston O.D.). 23. Measure cylinder bore taper (A—C, B—D). 24. Measure cylinder bore out-of round (A—B, C—D). CYLINDER BORE SPECIFICATIONS Item New Part Wear Tolerance Bore I.D.
B43E,B43G, B48G, P218G, P220G 82.53—82.55 mm 82.68 mm -UN-29JAN90 Engine (3.249—3.250 in.) (3.255 in.) T260 Engine 90.488—90.512 mm 90.632 mm (3.5625—3.5635 in.) (3.5682 in.) Piston Clearance B43E, B43G, B48G, P218G, P220G 0.076—0.127 mm 0.28 mm M36402 Engine (0.003—0.005 in.) (0.011 in.) T260 Engine 0.178—0.229 mm 0.38 mm (0.007—0.009 in.) (0.015 in.) Taper B43E, B43G, B48G, P218G, P220G 0.13 mm Engine (0.005 in.) T260 Engine 0.08 mm (0.003 in.) Out-of-Round 0.08 mm (0.003 in.) If cylinder bore exceeds wear tolerance, replace cylinder block or have cylinder rebored by a qualified machine shop. If cylinder is rebored, oversize piston and rings must be installed.
The following oversize pistons and rings are available: 0.25 mm (0.010 in.) 0.50 mm (0.020 in.) 0.76 mm (0.030 in.) If piston clearance exceeds wear tolerance, replace cylinder block, piston or both, or rebore cylinder. Install oversize piston and rings. If taper or out-of-round exceed wear tolerance, replace cylinder block, or rebore cylinder. Install oversize piston and rings. M98,2030K,33 -19-11FEB87 30 20