HR173 dipstick explode

[rhughes44]

I started my trusty old HR173 today and after about 10mins of normal use there was a loud bang - and the dipstick blew off together with a small quantity of oil.
The dipstick had a crack, but still screwed back into the casing. Any ideas on cause? Would it be safe to buy another dipstick, change the oil and continue to use the mower?
Any advice would be most appreciated!

 

[Rivets]

I suspect that you now have a major compression leak into the crankcase and you are going to have to do some searching. Fastest way to find the cause is to do a cylinder leak down test. This will pinpoint the cause, which could be bad head gasket, bad rings, a bad valve, etc.