GXv620 gjagk 1004901

Has the mower been tipped up? if so sump oil can travel through the breather and into the air filter soaking it in oil which then in turn burns and smokes, remove the air filter and see if is soaked in oil.
There are other reasons, engine over filled with oil, engine breather blocked, engine worn.

check and change the oil it some times the oil become weak and the engine can lift it up and out. also over filled oil is more easy for the engine to life it up and out. check the sump breather aswell make sure its not blocked.

Check the oil to make sure you don't have gas getting in your oil. If that's not a problem then you may have a leaking head gasket.

Gas filter might not run properly and it must be replace. If it gets bad enough the lawn mower might not turn on and in worse case gasoline could start coming out the air pusher.

I do not think this is a gasket issue, if the machine has beed tipped up oil will travel up the breather tube and enter the air filter case, over filling will also cause this, if its been tipped it will clear if you run it for a time with the filter off.

If the mower has been tipped up oil will now have entered the air filter box and soaked the paper air filter, remove the filter and run the engine to see if the oil burns away and the engine runs normally, do not over fill the engine with oil, fill only to the max mark on the dip stick.

This is probably not a blown gasket issue. A bad head gasket can allow oil to enter the cylinder head/combustion chamber if it's not sealing off the valve area. A simple suggestion is to check on the engine opposite the carb side for the oil/crankcase breather. It will have 2 screws holding it onto the block. It has a type of filter media in it that traps excessive oil and oil vapors from the engine. It is also connected by a tube to the air filter housing. When you tipped, you probably put too much oil in the breather and it was inducted over to the air filter/carb intake side.
Clean or replace the breather after checking it and also make sure you haven't overfilled the Briggs with oil and only use SAE 30 in the engine. Muti-viscosity isn't recommended in summer unless you run synthetic, then it is OK.
Please vote on this solution.

if unit is ohv engine - i gather unit is using oil ?

may have a blown head gasket and air filter may be oil / petrol soaked
restrcting air flow

check oil level is correct ( and does not smell of petrol ) wet sumped and breather is working ( not stuck closed )

check for tight valve clearance

if all these are ok then might suspect worn rings / bore ?


may need further info on engine model - type

let me know and i will try help more if can

cheers

unless the ground was a steep slope while mowing or the mower was tipped over 35 degrees or more in any direction except with the handle bars down (spark plug up is ok), it will most likley be a blown head gasket between the pushrod gallery and cylinder. remove the head and get it re-faced then assembly with new gasket. valve adjustments are 4 thou inlet and 6 thou exhaust

sounds like you have a blown head gasket....pull spark plug and check for oil on plugs....thats your bad head gasket