Which "16 hp Briggs twin" out of the possible dozens of models?
OHV, opposed??????
IF OHV, I'd GUESS head gasket for a start.
Post the Model & Type#'s or the Sears 917.xxxxxx number of the tractor so we can identify WHICH engine.

It's not an ohv but the model number is 917 255880

How about going directly to the engine and getting the Model # and Type # of the ENGINE and posting them.
The 917.255880 number you posted shows zero results when fed to several websites where manuals may typically be found. And that usually means the number given is not correct in some way.

My apologizes it's actually 917.255850 I I will also tell you it's a hydrostatic auotomatic as well

That appears to be a YT16-
Engine is likely a Briggs 402707-0157-01

Is it a vertical shaft?

Have you smelled the crankcase for the presence of oil?
IF the carb is leaking through, gasoline ends up in the sump, diluting the oil to point it easily gets past the piston rings.
My other "guess" is a bad crankcase breather.

I have not smelled the crank case but I cleaned the carb and I'm going to change the oil to sea if that helps I'll cheak th breather as well thanks

Yes it is vertical by the way

I also neglected tosay that there is a hoe that leads from the carb to the engine and there is bits of oil in it every time it runs for while I didn't think that might be a problem but it may be

There is a hose that leads from the carb to the breather that seems to have oil in it as well does that have any impact?

First thing I'd check is the air vents on the engine. I had mice built a nest on mine around the air/cooling vents which caused to it overheat and possibly blowing a head gasket that I had to replace.

You had best remove the tin cover that surrounds the cylinder-s, and clean out the mouse nests and poo that is obviously in there! That in itself will cause over-heating, and eventual big engine troubles.
Yes, you will get oil in that short hose, as it is the crank-case breather hose, to the Carb.
As another person said---smell the dip-stick tube, or if none, remove the oil fill plug, and smell the engine oil! If it smells like gasoline, then you have gas in the oil, which will destroy the engine in a short time. Change the oil!
Mice and other rodents dearly love the cover-s over and around the cylinders, and make their winter nests inside those parts. When you put the machine away for winter storage, lay some clothes dryer sheets arround the engine-s, and those critters will stay away! Works for me! Rusty Jones

Thanks Rusty. That had happened to me last year but didn't notice it until 1 of the piston rods broke and it was making an odd sounds. I cleaned it all out after replacing the rod and did the proper adjustments. It worked fine the rest of the year. I'll be checking this time in the spring for any nests.