What color were the plugs ( the spark electrodes and insulator ) that you took out? If they had a whitish or light gray color, indeed the engine is leaning out (insufficient fuel). If the plugs had a light brown or tan color, the fuel ratio is about right and ignition problems are possible. If the plugs have a black color, the engine is starving for air (too rich). Too rich usually tells on itself by producing black exhaust with a heavy fuel smell and does not result in backfire. Likely cause of leaning out would be fuel pump is failing (provided carb and fuel hoses are clear) Blockage of the fuel line by sediment or foreign objects in tank is possible. If this condition comes on gradually after a few minutes of mowing but not as soon as you crank it up, check that the fuel tank cap vent is not blocked. You can check this by running the machine until condition occurs and loosening or removing the cap. If that clears it up, clean out whats clogging the vent.

It does sound like a fuel problem, you did check the air filter didn't you? Have you got a good blue-white spark at the plugs? Always check the simple stuff first. I run Sta-bil in the fuel year-round plus some Marvel Mystery oil(mine are all older units designed for leaded fuel). A little speck of dirt in the carb in the wrong place can sure make these small motors run terible.

plugs were a whitish grey color, which yes, is indeed a lean burn. fuel pump seems to have good flow. yes, I did check the air filter, its not all that dirty at all, I did notice some oil in it though...would that have something to do with it? someone said that a little oil in the filter is normal as uneven terrain will sometimes cause sloshing of the oil in the crankcase and in turn will get sucked up by the breather...

Does it start running poorly when you throttle it up
only? Then run crappy when you put it in gear or engage the deck?
If so, then you likely have a electrical problem,
probably near the seat switch. Might just be partially
disconnected. If nothing is readily visible, you might
just disconnect the kill wire going to the coils and
see if it runs better.

Fish

If above suggestions don't do the trick, might try removing the hex headed plug at the lower right side of the carb. Beware that gas will run out and take safety measures with this in mind. It could be that you have water/crap in your carb float bowl. Blow compressed air in here if available.

Look for cracks in the vacuum line running from the block to the bottom of the fuel pump.

I would not think these symptoms would indicate Ignition Pack.

Check that Intake Manifold mounting bolts are tight to block.

Walt Conner

Thanks Walt, i'll give that a shot.

Does it run good when you throttle it up, and not engage the deck or trans? Or just when you throttle it up AND put
a load on it? What about engaging the trans on low throttle?
Fish

Well I should have asked for model numbers first since I don't really know which engine you have.

Walt Conner

I was wondering which engine you thought he had,
a l-head twin?

Fish

Its a v-twin vanguard, model 315777

That wasn't me posting. (grin)Those do have an Intake Manifold problem sometimes though.

Walt Conner

I know, can you reply to at least 1 of my questions?

Fish

Since you are back here posting, looking for help.

Fish

Not meaning to be a jerk, which I am good at, but does it run good at full throttle, but not engaging the deck or trans??

For you to get any real help, you need to slim down some of these variables. What brand/model nos. of tractor?

I could tell you to pour stabil and Marvel Mystery Oil
over the manifold, and then you might respect me enough to respond?

Walt has morphed into a God here, but I have not been here much due to the pop-up crap, and I am on dial-up,
but I have helped one or two people here.

Sorry for sounding bitter, I just am

Fish

I would read the instructions on a can of carb. cleaner and use them, plus find the fuel bowl vent and spay some carb. cleaner right in the bowl.

Just cause the air filter don't look dirty don't mean it's not plugged up. I would remove the air cleaner and see if that helps thus ilimating the the air part of the air/fuel mixture.

go back to the original post, and sort it out.
"but when you increase the throttle AND put any kind of
load on it at all".

Hence my questions.

Hey Fish, I do not want that kind recognition. I am trying to not post very much and will try harder.

As for your pop-up problem, if you will just download and use free FireFox for a browser, 99% of your pop-up problems will be over.

Walt Conner

it used to run good at full throttle with no load, now with or without load it still sputters and misses and backfires at full throttle. I really believe it is a fuel starvation problem but it doesnt make sense because it has great fuel flow all the way to the carb. I tried seafoam in the fuel and cleaned the carb with it as well, even dumped a scoche in the oil as well, doesnt make a difference either way. brand and model of tractor in orig post...not that it makes a difference, its not the tractor is the engine.

removing the air cleaner makes no difference.

its not backfiring through the carb so that leads me to believe that its not an internal engine problem. (i.e. stuck valve)

i think its time to get her to a mower shop.

My thoughts are to throw a few oz. of Gas Dri in the tank.
Sounds like water in the fuel.

Just raising a little heck, Walt. A evil sense of humor......

That is the challenge here, because if you have already
made a post, you usually nail the problem right off, and there is no further need for me to post..........

You have become the heavy hitter here, because you have
consistantly helped many, many people here, and people that
do this, rarely get the recognition they deserve. Think
of the thousands of dollars you have saved the posters here,
and that is something.

To the original poster, I would suggest just removing the rocker arm covers, and that will likely tell you what
you need to know, just takes a minute, and a wrench.
Then turn the flywheel by hand, and look at the valves.
One of them is likely stuck, or something like that, or a
pushrod is out , or something, and a valve not opening.

Fish

Fish, since you were the one who mentioned a possible electrical problem such as a faulty safety switch, I'll give you all the credit. That is indeed the problem, if you bypass the kill switch, it runs like a dream! So instead of figuring out which switch is bad, im just going to runa jumper from the ground on the keyswitch to the kill switch wire and solve my problem.

Thanks again everyone for your help!!

I take paypal.......................

Fish

haha! just to follow up...it actually wasnt the problem. after mowing for approx 15 mins, im back to square one again. Tried adjusting the valves, regapped the plugs and nothing, still does it. Tomorrow, im going to tear the carba apart piece by piece and clean it, we'll see...

Insure your carb float not stuck.

just tore the carb comletely apart and soaked in laquer thinner for about 2 hrs, hopefully when shes all back together it'll run the way it should.

Looking at the last couple of days posts, convinces me
that you are a bogus poster, so let this thread drop "crazed".

Fish

We will not hop through any more hoops.

Fish

Time for a namechange.

Sorry Walt.

Guys, no joke - I have experienced the same exact thing. I have a 23 hp vanguard (only 1.5 years old). I changed everything I could - tore apart the carb - cleaned and still persist. A buddy told me about seafoam - added a couple ounces and within 30 seconds after firing her up - the rev was gone and she ran solid. Up until last night - it came back and now I am stumped. I've checked the gas cap, etc - It runs more solid when you pull the choke halfway - but this is rediculous!

If it is the same problem as I have, then one of your cyls doesnt have compression. It was only running on one cyl, thats been the problem this whole time. I had the valves readjusted and the problem went away...we'll just see how long before it comes back.

Whoa, whoa, whoa! At 11:56 today you said you had just soaked the carb parts for 2 hours in lakker thiner:-) What was the outcome of that escapade? Does she run like it should now?

that was yesterday actually. That was a complete and udder waste of my time to put it bluntly. It still ran like crap after, mostly because that was never the problem all along, it was my no. 2 cyl not firing due to lack of compression.

What is strange about the whole deal is I adjusted the valves once before and afterwards it ran great for about 3 mins, then it went back to firing on one cyl which led me to believe the carb needed cleaned (at this point I didnt know it was only firing on one) so then once the carb was cleaned, once again, it ran good for about 3 mins then started acting weird again, which is when I decided to start from scratch again because I knew I had missed a step somewhere...sure enough, if I would have only checked in the beginning to see if both cyl were firing, I would have saved a lot of time. Its all trial and error I guess.

We are all confused, eh?

So, what did you end up doing to correct the problem? Just rotate one of the jets?

Fuel pump diaphram. These engines are set up so lean right out of the box (Thanks to the EPA) they are always bouncing off of the governor. The updated fuel pump kits seem to work well in these situations perhaps due to a lighter spring weight. Laquer thinner is a bit harsh, I would stick to Gumout carb and choke cleaner (the big can is $1.82 at Wally) since you don't want to harm any rubber parts, the blended fuels are taking care of this aspect already. There is also enough mtbe in the fuel so dri gas is a no-no. I just put a kit in a 16 hp IC twin for a guy (16 hp) with stellar results.

Hey guys - I just read through all these posting since I have the same issue. Just bought a used Yard General with the 20HP Vanguard. Cut the yard twice beautifully - starts like it should, runs like it should. The last time I let it run out of gas. Once I refilled, it started up (not without a little effort to get gas back to the pump I suppose). It only ran about 20 seconds till I engaged the blades, and she started stalling till finally died. Wouldn't start till I pulled the gas line going TO the filter, let it drain out of the filter, tried and it started right up, for 20 more seconds. Same issue - won't start. Here's the strange thing - I can hear and see a rhythmic squirting sound from the carb, and see pooled gas in the bottom that gets disturbed each time I hear the sound. Its like the fuel pump is squirting gas in - all while nothing is running and battery disconnected. Thought at first it was vapor lock - took off the cap, pulled on the diaphram there, thought it was fixed, but died again. Anyone got any ideas? If the fuel pump loses its prime, is there some special procedure to follow?
Thanks in advance!
Mike

YOUR VALVES ARE BAD

Could it be a used mower is like a box of chocolates? You never quite know what your getting until you bite into it. That used mower was sold for a reason, did find out that reason? Have you used some of the savings to take it to a qualified B&S service tech? I'm sure there is a answer to your issue but sometimes the answer costs a buck or two.