2008 Polaris ATV Sportsman 300 400 H.O. Service Manual, Page 65Get this manual
ENGINE (300) Combustion Chamber Inspection
Clean all accumulated carbon deposits from combustion chamber and valve seat area with soft wire brushInspect the combustion chamber for cracks andor damage from foreign debris
Coil fatigue Squareness
Cylinder Head Disassembly WARNING
Wear eye protection or face shield during cylinder head disassembly and reassemblyCylinder head service should be performed by technician knowledgeable in cylinder head reconditioning in properly equipped shopNOTE: Keep all parts in order with respect to their location in the cylinder head1Using valve spring compressor, compress the valve springs and remove the split keeperNOTE: To prevent loss of tension, do not compress the valve spring more than necessaryRemove spring retainer and springIII.2 5Remove valve sealsNOTE: Replace seals whenever the cylinder head is disassembledHardened, cracked or worn valve seals will cause excessive oil consumption and carbon buildup