Chainsaw Repair

Get it started on idle as best you can. Then remove the starter recoil to expose the flywheel (be careful- the flywheel will be rotating) Grap a can of carb spray or similar and hold up a bit of cardboard or similar against the air filter housing to prevent any spray from the can going near the air filter. Then while the engine is still running, spray some of the carb spray around the flywheel area- if you have an air leak through the crank seals, then the revs should increase almost immediately and then die back down. Do it two or three times to be sure. Like i say- make sure you don't get any near the carb/filter area as that will give you a flase reading. Another tell tale sign even before you do the spray trick will be a lot of oily residue inside the recoil housing around the flywheel area- this being caused by the fuel/oil vapour escaping from the crank seal. Hope that helps, as doing a complete leak down test is quite labour intensive and you will need special tools to conduct it- this method at least confirms the problem.