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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, removed and cleaned PCV valve.
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.

It's probably needs the piston rings replaced. Bad rings let oil pass into the combustion chamber and it is then burned causing blue smoke.

With 3000 hrs I would say it sure wouldn't hurt to be thinking about a over haul. Sound like you already did a lot of work on it. Make sure your exhaust system isn't plugged, It sounds like you have checked the crankcase vent system. You did check your valves when you did the head. The only things left is pistons and rings.

Thank you for the quick replys, and I had thought about the doing the rings but Im still getting good compression in both cylinders and when I pulled the heads I didn't find oil in the cylinder or in the push rod galleys. Even if the rings are bad I would still expect the engine to run better than it is, it may not have much power and it would smoke but I would think it would still idle with out being fully choked.
I realize that the rings are probly the next logical step but Im really trying to avoid that because ill have to have the block honed, and Ill have to buy another 60 dollar head gasket kit

Is there anything else anyone can think of before I bite the bullet and do a full 100% tear down?

Thank you all for the help

That is what I was thinking that if it had good compression the rings should be good. Check that carburetor one more time. Just because it is new may not mean it is good. Make sure you do not have a leak at the carburetor gasket being as how it was replaced. It may be allowing air in seeing as how you have to choke to stay running. Try spraying some starting fluid around seal while running to see if it smooths out. My:2cents: Hope this helps. Also if you are getting black smoke that points to rich fuel mixture ala carb.

I don't recommend overhauling this Vanguard with 3,000 hours. You can buy new Vanguards for less than the cost of an overhaul and get a 24 month warranty. You need all the numbers following the 303447 to be able to research a direct replacement. The 3rd group of numbers is the manufacture date and factory info.
You can checkout Small Engine Warehouse and Tulsa Engine Warehouse. I have done business with both, but I prefer Tulsa Engine Warehouse, just my opinion.
Mad Mackie in CT:biggrin::laughing:

As I said before did you check for a plugged muffler? I have seen baffles break off and plug them.

The only thing I could think of would be scored bores or worn piston rings. Sometimes they can be scored/worn in a way that it lets oil in but keeps good compression.

I suppose it could also be the exhaust as Reynoldston said.

Try a leakdown test. This test checks the sealing capabilities of all compression components - rings, valves and gaskets.
This is a special tool.
If you dont have this tool, try a cylinder balance test. You may find that 1 cylinder is working and the other cylinder is not due due to the rings.
Iv had a 14hp v twin vanguard do this and it was the rings not pulling fuel into cylinder and also that worn causing the smoke.
Earth out 1 plug at a time and record your results.
If when you earth a plug out and the engine cuts out, the problem will be on the other cylinder.

pugaltitude said:

Try a leakdown test. This test checks the sealing capabilities of all compression components - rings, valves and gaskets.
This is a special tool.
If you dont have this tool, try a cylinder balance test. You may find that 1 cylinder is working and the other cylinder is not due due to the rings.
Iv had a 14hp v twin vanguard do this and it was the rings not pulling fuel into cylinder and also that worn causing the smoke.
Earth out 1 plug at a time and record your results.
If when you earth a plug out and the engine cuts out, the problem will be on the other cylinder.

Click to expand...

Thank you all very much for the time and thought, Id love to do a leak down test and I know how to perform one but I dont have the tool and I wouldn't know what to make of the results :frown: hehehe. how long should it take for the pressure to bleed out? what kind of pressure should I be getting to start with? (im getting 110 psi in each cylinder cold, add a little oil to each cylinder and I get 120 psi) Im guessing that a large differance in bleed out time between the two cylinders would be a red flag, also remember I can't really warm this engine up much cause its runnin so bad.
What is a cylinder balance test and how do I perform one?
As far as a clogged muffler goes Ive pulled it off and run it with just the exhaust manifold and it still does the same thing so Im pretty sure its not the muffler.

Www.sedkc.com. Try this place . I get new crate motors very cheap - all few years old new stock surplus .

ok guys got some new developments, with the MUFFLER OFF I sarted the engine up, and like before It needed full choke and about 50% throttle and smoked heavly for only a minute or two, then the smoking almost completely stopped. At this point I slowly took the choke out little by little until it was off completely then I messed with the throttle going from full to idle and eveything in between. Still no smoke and the engine seemed to be running happily with a slightly rough idle and heavy backfireing when ever throttle was quickly reduced. I decided to take the machine out for a test drive and it did pretty well, seemed to be lacking a little bit of power and would die under heavy sudden load but would start right back up.
I investigated the muffler closely and foud some cracks on the back side of it and after banging on for a while I managed to get about a 1/4 cup of what looked like rusty carbon out of it, some chunks but mostly powder. at this point nothing else is coming out of the muffler and I dont hear anything rattleing around inside it.
So after letting the engine cool COMPLETELY I crossed my fingers and tried starting it up. But it did the same thing, needed full choke and 50% throttle to run until it hit operating temp, only then could I dump the choke and play with the throttle, however the smoking seems to have stopped for the most part, I would say its atleast 90% better but smokes significantly more on cranking start up and when shutting down.
At this point Ive got an engine with no muffler, that needs to be choked till it warms up, doesn't handle sudden load well at all, moderate all around power loss, smokes a little bit, and back fires when throttle is reduced quickly.
Who wants to take a stab at it now??? ALL input is welcome

Thank you all again for taking the time to help a stranger out

I think you have a leak down test mixed up with a compression test.
A leak down test uses compressed air to flow through cylinder head and if any leaks from compression related components shows on a guage, red being bad to green being good.

A cylinder balance test is a test to see if maybe its only running on 1 cylinder which if lost a lot of power could be your problem.
you need to put a wire from engine earth and connect to metal connector on plug lead at spark plug while engine running. If engine cuts out its only running on one cylinder so problem would be on other cylinder.

I think think THIS could be your problem.