Briggs 13 hp motor blows

[professor]

I have a JD rear engine rider with 13 hp Briggs engine that I use for triming. I bought it new in 03 and haven't used it much. The other day it started to miss and the plug was fowled. I cleaned the plug until I could get another. Yesterday it started and in about 5 minutes it started missing again. I checked the air cleaner and it was gas/oil soaked. I started it while the air cleaner was off and gas/oil shot out the opening as if it was under pressure. Is the problem a valve, broken ring or what? Thanks for any help.

 

[gator]

Had similar symptoms (miss and gas and not oil) blowing back through carb on 12.5 hp briggs. Pulled head and found intake valve seat had come loose and fell onto intake valve keeping it from closing. JB Welded the seat back in, let cure 24hrs, put head back on and it runs good now. May not be problem with yours but might be worth a shot.

 

[elad]

It's possible the exhust is plugged or is plugging up causing back pressure.
Recommend cleaning that before more serious things are considered. elad

 

[Stimw]

Good chance it is the carburetor float letting gas into the intake where it will go past the rings and into the oil with the engine off. When the oil is over full it will go through the crankcase breather to the air filter/carburetor. If your engine oil is way over full and the gas tank is empty that's what happened.
YOU NEED TO CHANGE THE OIL ASAP. Don't run it or it will seize the engine. Also need to find out why the float stuck. Might just be a piece of dirt in the needle valve.
I have seen this happen a few times with Briggs engines.

 

[professor]

I am sure that it is a broken ring. Is the engine worth repair or do I need to look for another 13 hp engine?

 

[dqdave1]

If cylinder wall is not grooved from broken ring; change the ring set.