The Gasket Genius large service kit fits Stihl 021, 023, 025, MS210, MS230 and MS250 chainsaws, containing one spark plug, one air filter, one fuel filter, one oil filter, one fuel pipe, one oil pipe, one exhaust muffler gasket, one carburettor gasket and one oil pump worm gear. Beyond the standard filters, pipes and spark plug covered in a routine service, this larger kit also renews the muffler and carburettor gaskets that seal the exhaust and intake joints, plus the worm gear that drives the oil pump off the clutch drum. Left worn, any of these can cause hard starting, an exhaust or carburettor air leak, or reduced oil delivery to the guide bar. Fitting this kit covers all of them in a single, more thorough service.