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stuck valve??


dav

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tried to start the Big Ten with a 243431 motor, after letting it sit for over 2 years. cranks over well but wont start. best i got was an occasional burp back thru the carb and a flash of flame. did get a backfire that severly damaged the nonstock muffler, too. my guess is the intake valve is sticking. looking for a second opinion here. if it is a sticking valve, is there a fix that doesn't require disassembling the motor? thanks
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It could be the valves,,If you damaged the muffler in the backfire just maybe you sheared the alum key in the flywheel, That setting two years with gas in the carb may not be a good thing either, my JD-110 set two years and the carb was a mess, & didn't start either. and it burped through the carb and fire shot out the muffler, either way, Good Luck.
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I'd bet on a stuck valve. Remove the head and check it. You might get lucky as I have on old engines...sometimes, anyway. If the intake is stuck, run a good penetrating oil down the stem, turn the engine over until the exhaust is open. Try pushing the valve with your fingers first. If no luck then, more penetrant, and a light hammer might do the trick. The same trick will work with the exhaust valve. If still no luck, remove the carb or muffler so you can see where the oil is landing. Be certain it is where the stem disappears, and try the valves again. If it was in the dry for only 2 years, it should loosen for you and run with no problems. You will have to clean the innards of the carburetor, chances are that the needle is stuck, as well as a valve.
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Take the spark plug out and pour in an ounce or two of penetrating oil and let it set for a few min. you might get lucky. You could use carb cleaner but only if you change the oil after.
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well, i pulled the head. boy, was that easy!! but the valves aren't sticking. i can tell by the amount of oil riding on the rings that either the rings are stuck or just plain worn out. put the head back on,. sure helps to have a pile of head gaskets. i will pour some marvel mystery oil down the plug after the weather clears. (i've been working under the grapefruit tree and it is windy as heck. no sense tempting fate!) the motor never smoked or used much oil so i hope it's stuck rings. if not, i have another motor, already rebuilt, sitting on a bench. then it will be back to finding why it's giving me a hard time.
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Stuck rings will not cause the backfire, nor will they keep an engine from running, unless the compression is so low that it will not fire. As you likely have the head back on, run a compression test and see what you have. Was the engine running when you parked it? The backfire that destroyed the muffler did likely shear the flywheel key. You will have fire, just not at the right time. Replace the key, kind of a pain with the engine in the tractor, and try again. Also, take the carb down and clean it. If it had ethanol in it, the needle is definitely stuck, and oxidation is present in places it should not be. If I know I am going to let something sit for a while, I always drown it with Marvel Mystery Oil, and drain the gas out of the bowl. YOu have to clean the plug before you start it, but that is easier than trying to figure out what might be wrong with it.
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I agree with clean bee Sure sounds like a valve to me.I know that you had the head off but a little bit under the valve will cause that problem.Had that happen on a wonderboy 700. Bob
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Did you replace or clean the points and replace the condenser? Did you disassemble the carb and clean it and replace the fuel filter or screen? I assume you drained it and put fresh gas in. Do the simple stuff first before you start tearing into it.
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  • 2 weeks later...
well, i was going to figure out the problem but then said, what the heck...i rebuilt the other motor to use on this tractor, why not just do it?? so the rebuilt is in the Big Ten. had some minor problems, like the intake manifold was wrong and the s/g belt was stretched (was tight enough on the old motor so i think the flywheel pulley must be worn more on the rebuilt) and natch, the battery didnt have enough charge to start it yesterday. today it fired right up...for 3 seconds. seemed to be running out of gas. no strainer in tank. new filter in line. drained tank, not too bad. new gas, did find that the fuel shut off valve has to be open ALL the way to get adequate flow. filed points, fired it up and drove it onto the trailer. tomorrow at the show i'll hang the grader blade under it and the 'dutch' blade on the front.
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