McCulloch Pro Mac 850 805 800 SP Piston Kit 2 1/16 In 92519

Piston kit for the McCulloch Pro Mac 850, Pro Mac 805, 800 SP and Super Pro 81 chainsaws. 2 1/16 inch bore, which is 52.39mm. Replaces McCulloch part number 92519. CONTENTS. Piston, ring set, wrist pin and circlips. The cylinder is not included, so this is the kit for an engine whose bore is still good. Gaskets and crankshaft seals are not included and both are worth replacing on a saw of this age while it is apart. THE BORE IS IN INCHES. McCulloch specified these engines in inches rather than millimeters, and built this family in more than one bore. Read the size off the old piston or measure the cylinder before ordering. Horsepower and model year are not reliable guides on this family. WHAT TO DO WHILE IT IS APART. On a saw of this vintage the crankshaft seals have usually hardened whether the saw has been run or not, and a hardened seal leans the mixture out and will take a new piston the same way it took the old one. A perished impulse line does the same thing. Pressure and vacuum test the crankcase before reassembly. ON ASSEMBLY. Check ring end gap in the cylinder the rings will run in, and side clearance in the piston grooves. Hone the bore lightly, use a ring compressor, fit the circlips with the open end away from the ports, and turn the engine over by hand before you start it.

• 2 1/16 INCH PISTON KIT FOR THE PRO MAC 850, 805, 800 SP AND SUPER PRO 81 - Piston, rings, wrist pin and circlips, replacing McCulloch part number 92519. These are the big-bore professional saws of that era and they are worth rebuilding, which is most of the reason this part is still made at all.
• THE BORE IS IN INCHES ON THESE SAWS, NOT MILLIMETERS - This is the 2 1/16 inch piston, which works out at 52.39mm. McCulloch built this family in more than one bore, so read the figure off your old piston or measure the cylinder before ordering. Going by horsepower or by model year is how the wrong piston ends up on the bench.
• WHAT IS IN THE BOX, AND WHAT IS NOT - Piston, ring set, wrist pin and circlips. The cylinder is NOT included, so this suits an engine whose bore is still serviceable. Gaskets and crankshaft seals are not included and both are worth doing on a saw of this age while it is open on the bench.
• ON A SAW THIS OLD, CHECK THE SEALS AND THE FUEL LINE - Crankshaft seals harden with age whether the saw has run or not, and a hardened seal leans the mixture out and takes a new piston with it. The same goes for a perished impulse line. Pressure and vacuum test the crankcase before anything goes back together.
• ON ASSEMBLY - Check ring end gap in this cylinder rather than the old one, and side clearance in the piston grooves. Hone the bore so the rings have a surface to bed into. Use a ring compressor, fit the circlips with the open end turned away from the ports, and turn the engine over by hand before the first start.