SYNCHRO-BALANCERotating & Oscillating CounterbalanceFig. 3 -- Installing and Timing PTO Drive GearThe counterweights and ball bearings are an integral partof the covers, and cannot be removed. Lubricate the ballbearings and gears with a few drops of engine oil.PISTON MUST BE AT TOP DEAD CENTER.Remove the timing hole screw from cover assembly.Fig. 4. Insert a short piece of 1/8" (3.18 mm) rodthrough timing hole in cover and into maching hole incounterweight. Fig. 4. The rod holds the counterweightin the proper position while cover is installed on engine.Fig. 4 - Removing Timing Hole ScrewInstall cover assembly and gasket. using care to avoiddamage to oil seal and making sure that bolt holes lineup with tapped holes in cylinder. To minimize gearbacklash. push magneto side cover toward idler gearand torque bolts to 120 inch pounds (1.4 mkp or 13.5Nm). For MODEL SERIES 300400 and 320400 repeatabove for PTO cover, torquing bolts to 200 inch pounds(2.3 mkp or 22.6 Nm).Remove timing rods. Coat threads of timing hole screwwith a non-hardening sealant, then install screw and fibresealing washer.MODEL SERIES 251400, 252400 &253400These Model Series utilize two gear drivencounterweights in constant mesh with the crankshaftgear.The cut-away view illustrates these gears, mounted inthe crankcase cover, and how the Synchro-Balancecounterweights rotate in opposite direction to crankshaftrotation, Fig. 5.Fig. 5 - Aluminum Engines Rotating CounterbalanceSystemSERVICE PROCEDURES FOR MODEL SERIES251400, 252400 & 253400The gear driven counterweights must be properly alignedwhen cover is installed.2
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