Motor starts, dies immediately

[TnRiver46]

9 hours ago, J Francho said:

I can testify to this.  My current rider needed carb work.  I opted for a new carb since it was a little more than the parts and easier to replace the whole thing.  I am not much of a 2-cycle guy, but my son is and I haven't bought any new lawn equipment in well over decade.  My boat outboards usually go to a Merc technician, though I've changed a starter, and always winterize myself.  I look at this way: my lawnmower poops out, the grass gets long.  My outboard poops out, and I might be stuck out on Lake Ontario floating to Canada.

Definitely easier to replace carb that clean them on a mower! 

[Way2slow]

Lets see, a ebay carb cost approx $15 that fits, but may or may not work.

An ebay kit cost approx $15 that may or may not fit, and still may or may not work.  

It takes 15-30 minutes the swap out the carbs.

It takes an hour or so to remove, clean and reinstall the carb, that may or may not work.

I know which one I would do, but when I'm sure it's the right carb, I turn around and reorder a second for next year.  I keep a spare ebay carb for every chain saw, weed eater, tiller, push mower etc I have.  They don't have one of those cheap ones for my Gravely Zero turn or I would have one for it too.  

 

[livemusic]

Yes, I had saved the old plugs and marked which is which.

 

I took it to the lake and it seemed to do slightly better but not a lot. Yesterday, I put an inline spark tester on and found each cylinder (four) to be firing. I also took the fuel line off and tried to run it from a clean gas can with clean fuel. It really didn't seem to do any better but after I reconnected the fuel line to the boat fuel tank and kept trying it, it was like it just kept getting better and I have since cranked it several times and run it with the water hose muffs and, yippee, I am able to advance the throttle forward and back and as long as I have a bit of rpms, it runs fine. If I go back to idle, it eventually dies.

 

I am still not 100% sure about this bulb/fuel line. I probably bought it a few years ago at Basspro or Academy. I am not confident it is pressuring up right and staying pressured. As I said earlier, a mechanic told me one time that these mainstream lines/bulbs are terrible and he could make a better one. Is there one I could buy that is high grade? Other than that, maybe it needs idle adjustment. Fingers crossed I don't have to take it to a recommended mechanic, as it will likely be weeks there in this busy season. I am going to call him and ask if he can build me a line/bulb but he will probably say he is too busy, that is what he said before.

 

I find it interesting that with the old (really bad-looking) spark plugs, once cranked and going top speed, it would do 29mph by GPS. Same top speed it has always done. After I put the new plugs in, it hit only 28mph. (Same model: Champion L78V spark plugs.)

[InfantryMP]

There should be an idle adjustment screw that can be made on the carb to help with the idle issue. Maybe try increasing the idle a little bit on the carb to see if it helps. You do not want it crazy high obviously, but it could be a small adjustment that can help you here.

[TnRiver46]

35 minutes ago, livemusic said:

Yes, I had saved the old plugs and marked which is which.

 

I took it to the lake and it seemed to do slightly better but not a lot. Yesterday, I put an inline spark tester on and found each cylinder (four) to be firing. I also took the fuel line off and tried to run it from a clean gas can with clean fuel. It really didn't seem to do any better but after I reconnected the fuel line to the boat fuel tank and kept trying it, it was like it just kept getting better and I have since cranked it several times and run it with the water hose muffs and, yippee, I am able to advance the throttle forward and back and as long as I have a bit of rpms, it runs fine. If I go back to idle, it eventually dies.

 

I am still not 100% sure about this bulb/fuel line. I probably bought it a few years ago at Basspro or Academy. I am not confident it is pressuring up right and staying pressured. As I said earlier, a mechanic told me one time that these mainstream lines/bulbs are terrible and he could make a better one. Is there one I could buy that is high grade? Other than that, maybe it needs idle adjustment. Fingers crossed I don't have to take it to a recommended mechanic, as it will likely be weeks there in this busy season. I am going to call him and ask if he can build me a line/bulb but he will probably say he is too busy, that is what he said before.

 

I find it interesting that with the old (really bad-looking) spark plugs, once cranked and going top speed, it would do 29mph by GPS. Same top speed it has always done. After I put the new plugs in, it hit only 28mph. (Same model: Champion L78V spark plugs.)

For fuel lines, I also make my own. Just get some hose by the foot from an auto parts store. Add the bubble and appropriate hose clamps and you’re good to go! (No mechanic required).  It’s cheaper than the useless ones that come pre assembled too! Haha

[E-rude dude]

Since you had put seafoam in the tank .........

and it now seems to be running a little better, I’m more apt to believe your motor just needs a good de-carb. A maybe a few very small carb adjustments.
 

Did you check the gap on the new plugs?

Are the old plugs gapped to spec?

interesting that the new plugs are not performing better.

[livemusic]

I tend to agree with it needing a de-carb treatment.

 

The spark plugs are gapless; I had never seen them, had to research it. Old plugs were black and ugly but still functioned. New ones are turning black.

 

I went to lake again today. I've got the hang of starting it but it's still not great and sometimes, runs a bit rough. But when you get it going at speed, it seems to run like a top. If at lower speeds, if it wants to die, if I choke it a little, I can usually keep it going.

 

Top speed seems to be now where it was before.

[Alex from GA]

Like TnRiver said, buy some fuel line @ an auto parts store and buy a Mercury bulb not a Walmart or BassPro one, and replace it.  I have an older, '88 Merc 45hp, it's essentially the same engine.  4 cylinder 2 carb 2 stroke.  The carbs are a ***** to get off.  Did you take a compression check?  If not you need to.  The mixture screws on the front of the carburetors need to be adjusted to idle right.  Start @ 1 1/2 turns out.  Good luck.