Briggs Vanguard HELP!

[subergoo]

I have started this thread in another section already but I think its better suited here so if a mod wants to delete the other one please do so.
I have a 16 horse power Briggs Vanguard V twin over head valve #303447. This engine has about 3000 hours on it and has run great for the past 2999 and has been very well maintained all its life. Recently it lost power and started blowing blue/black smoke out the exhaust. This condition has gotten MUCH worse, its smoking so much now that it fills a three car garage in under a minute. It now only runs under full choke and has little to no power.
I then replaced the carb with a new one, new plugs sparking fine, oil changed, two new head gaskets, fully inspected heads and valves, compression checked out to about 110 psi on each cylinder cold, air filter good and clean, new intake manifold gaskets, new fuel pump.
After doing all this the engine STILL does the exact same thing. Only starts up and runs with full choke at 50% throttle or more, smokes like crazy, and still has no power.
HELP ME PLEASE.

 

[sizzami]

if you have good spark and compression the issue becomes valves or timing I think if it were mine I would pull the exhaust and have a look at the ports see if one cylinder is smoking more than the other a broken or stuck valve could make the one side starve for fuel while the other is flooded by choking it , thats my 2 cents

 

[tcartwri]

Pull the valve covers off and do a visual on the rockers, springs and guides.

check the pushrods to see if they are bent.

 

[subergoo]

Thanks for the input guys.The valves rods springs rockers and all other head related components were checked out when I did the head gasket, and every thing seemed fine. I was getting about 110 psi in each cylider cold, does this sound right? I then did the old pour a little oil into the cylinder trick and got about 120 psi in each cylinder which makes me think that the rings are ok... I also believe that valve timing may be a problem but I cant come up with a logical explination as to how the valve timing could change so suddenly or even what would cause a major change in timing with out sever and obvious engine damage.
Im totally stumped fellas... any other ideas or trouble shooting tests I could run? or am I stuck with tearing the whole thing apart
Thanks again guys

 

[murphy1244]

Did you just do a oil change?? Check the level, thats happened to me.

 

[RDrancher]

Watching this one with interest. The Vanguard 14 hp on my concrete saw started fine the other day then started smoking BAD when I gave it throttle...then quit. Oil coming out of the exhaust. Pulled the plugs and one was soaked. Cleaned off the plug and it fired up but did it again. Thinking maybe a ring?

 

[sizzami]

thats a good point I ruined my first motorcycle that way when I was twelve checked the oil with it leaning on the kickstand and overfilled it by a quart, smoke powerloss then nothing.

 

[mwb]

I suggest checking the drain for your valve guides, springs. Oil is pumped up there and should drain back into the crank. There is a rubber vent hose that feeds into the intake (remove fumes from crank) - is there oil in that line?

You can easily test this by running the engine without the filter and cover installed - there is no intake vacuum to pull oil from the valve cover. Does the smoking stop?

 

[subergoo]

Thanks for the input guys.The valves rods springs rockers and all other head related components were checked out when I did the head gasket, and every thing seemed fine. I was getting about 110 psi in each cylider cold, does this sound right? I then did the old pour a little oil into the cylinder trick and got about 120 psi in each cylinder which makes me think that the rings are ok... I also believe that valve timing may be a problem but I cant come up with a logical explination as to how the valve timing could change so suddenly or even what would cause a major change in timing with out sever and obvious engine damage.
Im totally stumped fellas... any other ideas or trouble shooting tests I could run? or am I stuck with tearing the whole thing apart
Thanks again guys

The oil was just changed and is the proper level. The PCV valve, crank vent, crank breather or what ever else anyone calls it is good to go too.

 

[subergoo]

and when I changed the head gaskets I didnt see any pooled oil in the rod galleys or on top of the pistion.
Im about ready to give up and tear it completely apart