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donmoore1904

10hp 243431 suddenly runs erratically above idle

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donmoore1904
I mowed for the first time yesterday, after a winter that was virtually absent of snow (very unusual). Thus I believe I ran the tractor only once 3 months ago or so. For the first 1/2 hour the tractor ran fine. Then suddenly it seemed like the spark or fuel was in trouble. No backfiring, but it acted like it wasn't firing evenly and was "missing". Since I have been remiss in checking the head for carbon, and suspicious I have been on the rich side, I cleaned it out. Looked good in there, and set the plug which was a little wide at .030. I recently did the points/plunger, and didn't stop to see if something got loose there. It then ran the same, though I noticed that if I backed the throttle off to a low setting I could get it to run normally. Good power and smooth running up inclines, though at a slow pace. As soon as I increased the throttle, not so good, except an occasional 30 seconds of mostly-normal operation at higher speed but indications full power wasn't there. Since we expected a lot of rain, and the grass was long, I finished at the low throttle setting. Suggestions? I'm guessing fuel and my stupidity for leaving it sit so long. Maybe a particle of dirt? Thanks.

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Willy
I would replace the spark plug,if the gape was at .030 it must have been in there awhile. I've found that the points or plug are the first thing to check,the points often get a film of oil on them,and you can clean them by running a piece of lint free paper like a dollar bill between the contacts. Spark plugs can look good but still not fire under a load. If these things are as they should be then dink with the carb, you can make more problems for yourself by getting your carb out of adjustment and then trying to trouble shoot the problem. Just my humble opinion.

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1Litre
Run the engine at the RPM it begins to run poorly. Pull the choke slowly to see if it gets better or worse. If it gets better you should be able to adjust the High speed mixture screw to take care of the problem. If worse it is mos likely the ignition problem and the guys have the info on here to help with that.

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MysTiK
If it ran well, and then was stored indoors for long period, and now runs like crawp, I'd be tempted to try SeaFoam in the fuel tank. I'd also switch to premium fuel to avoid ethanol gas separating into layers, and water absorption - dump old fuel. "Stabil" seems to help stabilize ethanol gas; but I don't think that's 100% either. After using Stabil over winter, I notice that a new fillup w fresh gas works better. But if there's still goo deposits in there, that's where SeaFoam might save the day. SeaFoam also comes in a spray for carb. Other possible solution is carb cleaning, and most of this writing is an attempt to avoid that. All of this talk has been a very popular topic lately; there's lots of interrelated ideas here. It's hard to exactly say because, kinda like Willy said, people try a bunch of things at once, so it's hard to exactly say that one thing is the problem. Remembering what changes you made is a good thing; esp. if you need to undo it.

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toomanytractors
Remove the gas line at the carb and let the tank drain completely. Then drain float bowl and start over with fresh gas. You are probably suffering from phase separation which occurs when the gas and ethanol leave each other. I had this problem with a 3410 a while back and cured it in this manner.

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donmoore1904
Good ideas here folks. I was hesitant to start ripping stuff apart willy-nilly. I did that with the head, but mostly because I have been wanting to do that for almost a year anyway, and I knew I could complete it in a fixed amount of time. I'm going to start with draining the fuel completely, putting in some high test (which I was using and stopped), and tweaking the high speed screw slightly if needed. Then go up the ladder. Thanks for the advice. I'm leaning towards fuel since I did all of the ignition a year ago. The only thing would be if I left a screw loose somewhere other than my brain...

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donmoore1904
Yep, you guys were right to question my fuel. I emptied the tank and bowl, and put in some fresh premium. That seems to have done the trick. I mowed for an hour without issues of throttle position or persistent missing. If I have to be totally critical, I think I have a very occasional minor miss (maybe once every 10 minutes). After I did the ignition and rebuilt the carb, I remember the advice to use at least medium grade octane. I admit that I did that for several months, and then slacked off in the fall to regular unleaded. Between that and letting it sit, I think that was a problem. I'm thrilled to be back to hearing the transmission's new sound after its rebuild, and not the missing of the engine :D Thanks again for the great advice and being here.

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MysTiK
I would suggest a new fuel filter. If there's "goo" from separated ethanol gas, it seems probable that same goo could be caught up in the fuel filter. I have similar symptoms on my Briggs in my Pacer mower. The fuel filter is getting old. Actually there's a bunch of issues accumulating with that mower. It is demanding attention. But in terms of fuel delivery, I might have delivery that's borderline; and hence the hiccup now and then, as it corrects itself. The Pacer is a newer mower with all this shroud stuff and "strange things" connected to the shroud - omg - 8) and I don't know or understand it. So some mechanical experience for me is on the horizon. It's not getting any better as is. I'd rather fix it myself if possible; but down time could be a bigger problem. I will probably run a thread on this one soon. Should be really funny as this armchair mechanic fumbles to conquer the impossible. :D

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Johnrenk
Had trouble with almost every carb. I have, bought a gallon of cleaner from Pep Boys comes with a basket for small parts, dismantled carb let soak for over night, rinsed all parts in warm soapy water, rinsed in plan warm water , blow out with air, everyone ran like new except for one. Does not ruin gaskets or O' rings. Even cleane the 3 carbs on outboard boat motor.

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