547cc troy bilt engine 2015 trouble

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cxbxr.3

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So last week this started with a slight miss that cleared up on its own while running, now the miss is more pronounced & constant will shut itself off under a heavy load, very hard to restart, also sometimes it will back fire during a hard restart, then black smoke. Thought maybe it was running too rich & the carb was at fault, so I replaced the carb because I could not fine a rebuild kit for it. With the new carb it is doing the same thing, I checked the valves they appear to be in spec (lash), I have replaced gas in the tank twice to rule out bad gas. The only thing I can think of is either a faulty ignition coil or a sticky compression relief mechanism. What you think? Also seems to use more gas than it use to when all this started last week.
 
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The Specialist

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cxbxr.3 said:
So last week this started with a slight miss that cleared up on its own while running, now the miss is more pronounced & constant will shut itself off under a heavy load, very hard to restart, also sometimes it will back fire during a hard restart, then black smoke. Thought maybe it was running too rich & the carb was at fault, so I replaced the carb because I could not fine a rebuild kit for it. With the new carb it is doing the same thing, I checked the valves they appear to be in spec (lash), I have replaced gas in the tank twice to rule out bad gas. The only thing I can think of is either a faulty ignition coil or a sticky compression relief mechanism. What you think? Also seems to use more gas than it use to when all this started last week.
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There are a few things that you will want to check. But I ask about your valve clearance first. What did you have for a clearance?? You might want to check the flywheel key as well as it might be part sheared. If your flywheel key is O.K., you will want to look at the valves. They may have to be taken out and cleaned. Cylinder head might be full of carbon as well??? The back fire is usually a timing issue, but the hard starting can be a combination of both. I would need more information.
 
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cxbxr.3

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.005 intake .007 exh. it only hard starts when it shuts itself off in really high grass & under a heavy load & will sometimes backfire when restarting under those conditions, also backfires 2 to 3 times an hour of mowing randomly, cranks right up if i manually shut it off when warm or when cold. just seems to miss constantly mostly at higher rpm's but does it at lower too. How do i check the flywheel key ?
 
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To me this sounds like your engine is only running on one cylinder. Simple test if you have a GOOD pair of insulated pliers. You don’t want to be rudely surprised. With the engine running at 3/4 throttle pull one plug wire off plug. If the RPM’s drop that cylinder is working properly. Repeat on the other cylinder. If there is no change in RPM’s there is a problem with that cylinder. May be bad valves, bad valve clearance, bad head gasket, bad manifold or manifold gaskets or bad carb. If you do find a problem, post back and I will give you a procedure to narrow down the problem. If both cylinders drop, my guess is wrong.
 
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cxbxr.3

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It is a single cylinder engine 547cc i have replaced the carb with a brand new one, it is performing the exact same as the old carb. I have all new gaskets carb side also I plan on pulling the head & examining the head gasket next can someone point me in the direction of a good online guide or video to pull the head of this troy bilt engine ?
 
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cxbxr.3

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Have a question before I pull the head to replace head gasket, I would like to check the flywheel key. Does anyone know what flywheel puller I need for the mtd: 4X90HU engine ? Also by anychance know the flywheel nut socket size ?
 
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cxbxr.3

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Ok guys here's the update the mower is back to running great, thanks to a valve adjustment lol step dad did not check them right I went back & checked them and found the intake was way to tight (zero lash) replaced valve cover gasket & spark plug and everything is A-OK thanks again
 
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