Hydraulic lock a chainsaw ?

[treequip]

But how did it get into the crankcase via the carb, is the fuel under pressure and forced through the carb because the tank vent is blocked ? I have been tinkering with engines for 50ish years from Lambretta and BSA Bantam days and when they leaked fuel it was under gravity and any fuel in the crank evaporated leaving the oil so when you got a start it was very smoky till it burned off or it oiled the plug and wouldn't go

 

On such a small displacement engine you only need a little leakage to cause problems

[spudulike]

But how did it get into the crankcase via the carb, is the fuel under pressure and forced through the carb because the tank vent is blocked ? I have been tinkering with engines for 50ish years from Lambretta and BSA Bantam days and when they leaked fuel it was under gravity and any fuel in the crank evaporated leaving the oil so when you got a start it was very smoky till it burned off or it oiled the plug and wouldn't go

 

 

 

You know when you pull the fuel line off a carb and it pisses out a fair bit of fuel? This amount of fuel will find it's way in to the crankcase if the needle is shot or leaking and when you pull the saw over, the fuel will shoot up the transfers and straight in to the combustion chamber where it won't compress like gas as it is fluid and more dense!

 

The breathers in many saws only allow air in but hold pressure and wont let air out hence the pressure I mentioned earlier.