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This may get a little long, but niece is having running issues with her 3 year old JD LA 145 with a 22hp twin. I have never had an engine do this before, but here goes;

It ran fine 2 weeks ago when we last used it, then the next time it did not want to start. Had to use starter fluid and when it did start, it ran very rough and would not accelerate. Black smoke began to come from exhaust and the fumes would burn your eyes and nose. It sounds like it is hitting about every other stroke or so and barely running fast enough to idle. So far, this is what we have tried and found out.

The coils, plugs, wires, are all good. It does not have a firing problem.
All the safety switches were checked and are working as they should.
This pretty much eliminates an electrical problem.

The carb was removed and thoroughly cleaned as well as the tank. The fuel pump is working as it should and we are convinced it is getting enough fuel.
The compression in both cylinders is 150 psi.
The valves are all working perfectly.

So, this is what I was able to observe.
The engine will start and run smooth initially...uhh sometimes. Sometimes it runs as mentioned above for a while, then begins to run smooth after a few minutes.
When the engine runs smooth, it can be accelerated slowly, but when it runs rough, it can not.
If I try to increase engine speed too fast, it will revert to running rough again.
If I engage the blades while it's running smooth, it begins to run rough again.
Seems that anytime there is a sudden engine acceleration, or a sudden load such when the electric clutch is activated, the engine will revert back to running rough.

Whenever the blade is engaged, or the accelerator is moved too rapidly toward high speed, the gov. lever drops completely and remains there until I either lift it by hand, or the engine is shut off. It is not binding as far as the action of the lever and rods. It's almost as if when the gov. lever falls too low, there is something keeping it there until it is forced up or the engine is shut down.

We have had 2 very knowledgeable lawnmower mechanics to check it out and both are scratching their heads right now. Is it possible that the gov. shaft from the engine has slipped within the lever and is out of adjustment? Is it possible for the gov to go so low that it actually is being held down by the forces of the engine? Both gov springs are connected.

From what you say the first thing I would do is totally rebuild the carb. The black smoke indicates a rich mixture. I would be looking for either a bad needle and seat or bad float.

Is this a Vanguard engine, and has the air filter been changed recently. Briggs has two air filters that look similar and both will fit, the problem is one of them doesn't allow enough air flow and causes a rich run situation shortly after being installed, like within about 10 hours. It is a round air filter about 2 inches tall. If you have this air filter, start the mower and remove the air filter and see if it smooths out.

The air filter is off for all the testing that we did. Putting it on has no effect. Mower mechanic friend of mine (shade tree version) says these engines are notorious for valve seat failure and plans to check that out later this week if all else fails. He's already had to repair 3 engines this season for valve seat problems on V-twin B&S engines. All of them required head replacement due the extensive damage caused by the loose seat. I personally would have thought that if the valve seat failed, then compression would be lower than 150 psi. He plans to replace the carb with another known good carb, next. I still believe it to be a carb or gov. issue.

This may seem like a dumb question, as you have gone through the mechanics of the issue quite thoroughly, but how old is the gas you are using?

i still think it needs the carb done again....something was missed, is my guess

jtcarter1 said:

This may seem like a dumb question, as you have gone through the mechanics of the issue quite thoroughly, but how old is the gas you are using?

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The only dumb questions are the ones that don't get asked.

The gas was pump fresh.

reddragon said:

i still think it needs the carb done again....something was missed, is my guess

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Friend replaced carb with a known good one today. It had no effect on it. He and another mechanic checked it out today and he now believes what I had originally suspected before I let him take it to his shop. They both have come to the conclusion that the governor is having internal issues. Whenever it bottoms out on sudden acceleration, or when blades are engaged, it does not rebound easily w/o either lifting it by hand or by shutting engine off. Even shutting engine off does not always let the gov. rebound and when you lift by hand, it has a slight catch to it on occasion. He plans to inspect it next.

you can always set your throttle with a TACH manually and disconnect the governor...itll save you cracking open the engine

Well, it has been officially determined that gov. was broken (about half dozen pieces). He replaced the gov. , cleaned the engine and oil pump, and re-assembled everything. It only solved half the problem and there was still some spitting and sputtering. He then re-installed a known good carb and it runs great now. He re-installed the original carb and it went back to spitting/sputtering. Is it possible that the carb caused the gov to break, or vise-versa? It's weird that it had 2 problems going on at the same time. What do you think? Now we have to find a deal on a 79130 carb.

often times, governors are busted when when people[kids] try to gain rpms [hot rod] on their mower.....but it could just be metal fatigue too....i have the exact same mower and carb....they can be a bitch to fix......new gaskets and a sewing needle to clean those tiny bleed holes is usually effective...theres also ultrasonic cleaners too....but ive seen them break loose stuff and worsen the problem too....if all that doesnt work then get a proven/tested used carb [cheapest fix next to rebuild kit]....looks like you were hit with a double whammy....but at least its coming to a close:thumbsup:

reddragon said:

often times, governors are busted when when people[kids] try to gain rpms [hot rod] on their mower.....but it could just be metal fatigue too....i have the exact same mower and carb....they can be a bitch to fix......new gaskets and a sewing needle to clean those tiny bleed holes is usually effective...theres also ultrasonic cleaners too....but ive seen them break loose stuff and worsen the problem too....if all that doesnt work then get a proven/tested used carb [cheapest fix next to rebuild kit]....looks like you were hit with a double whammy....but at least its coming to a close:thumbsup:

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I find it hard to believe that it already had metal fatigue in only 50 hours running time, but since the economy has gone to pot, a lot of companies are taking a lot of shortcuts to keep profits up. Unfortunately, that sort of reputation will also kill them in the end.

you right on about that...unfortunately ...alot of these newer v twins [ briggs and kohler] have had poor manufacturing issues..the last briggs i had lost both connecting rods out of the blue....and it was well maintained...i hope my current one will do better......common issues are valve seats/head gaskets/pusrods...etc......i wish they just would have just put OHV's on their reliable opposed twins instead of ever coming up with the v-twin craze [ i hate odd fire engines]....but maybe im just getting old and grumpy :laughing:

bodean said:

Well, it has been officially determined that gov. was broken (about half dozen pieces). He replaced the gov. , cleaned the engine and oil pump, and re-assembled everything. It only solved half the problem and there was still some spitting and sputtering. He then re-installed a known good carb and it runs great now. He re-installed the original carb and it went back to spitting/sputtering. Is it possible that the carb caused the gov to break, or vise-versa? It's weird that it had 2 problems going on at the same time. What do you think? Now we have to find a deal on a 79130 carb.

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No, I've never heard of the governor causing the carb to mess up or vice versa. My cousin bought a new riding mower and it started knocking and kicking and clanging. We had no idea what it was. I wouldn't dis-assemble it because it was under warranty. The mechanic at the warranty shop said it was a broken cam of all things. But the governors usually don't require much adjustment really. I have seen them vibrate loose and have to re-position the governor shaft, and the governor arm, then bolt it back together. That's about it. Sorry to hear of the internal explosion!