OK to start mower engine with shroud removed?

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  #1  
Old 09-21-15, 04:28 PM
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OK to start mower engine with shroud removed?

This is an older Craftsman riding mower with 12hp b/s engine, Suspected broken connecting rod, so I started taking things apart hoping I could at least see flywheel key and eliminate that (I know minimum about engines but did a lot of googling--I did do some work on starter before). I want to try starting it again but do I have to put the shroud and screen and cover parts back on? Will anything fly off? The oil filler tube is just sitting loosely in place--it attaches to the shroud that I removed. Will oil fly out? The reason I want to try starting again is after reading more I determined that piston does seem to move when I stick a dowel into spark plug hole, also I can see it moving. But still, turning engine by hand I don't get much resistance like before. Thanks in advance for advice.
 
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  #2  
Old 09-21-15, 04:38 PM
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Piston

You will not have compression when the spark plug is removed; thus little resistance when turning the engine.
 
  #3  
Old 09-21-15, 05:32 PM
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The oil fill tube might stay in or it might not. If it comes out, oil will spray everywhere like a volcano. Are you sure the piston is moving, or are you seeing a valve moving instead?
 
  #4  
Old 09-21-15, 05:34 PM
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You can run it with it off BUT NOT LONG that is your cooling system.

What is your model and type numbers.

What are your symptoms ?
 
  #5  
Old 09-21-15, 08:21 PM
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Sears Craftsman 917.25464 LT12 (old Roper/AYP) 12 HP from 1989. I was mowing, loud noise like I hit something, shut off mower and engine, checked for obstacle, found stick in blades, assumed that was the problem, tried to restart but engine just spun freely. Strong battery and starter but engine did not catch. Came home and looked up symptoms and sounded like connecting rod. Pulled plug and looked in with light and stuck dowel in, turned flywheel by hand, could see and feel something (I assumed piston) move back and forth very slightly (no idea what normal is--had never done this before). I think I read if rod is broken, piston does not move normally, so I thought I'd start taking things apart to see what I could see, got down to just taking off all the covers, kept testing for piston movement, still moved, then thought I should try starting it again, that maybe it had seized up momentarily. That's where I am now--wondering if I have to put all the shrouds back on so oil filler tube is secure. PS I HATE to admit this but I had run the mower the day before with very low oil. It ran fine after filling for about 15 minutes when the above happened.
 
  #6  
Old 09-21-15, 11:00 PM
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Piston

Ok You gave a number for the mower

we need one for the engine. It's on the top or on the side of the engine on the sheet metal.

Take your spark plug out and turn the engine over. Put your hand or finger by the plug hole. If it blows your finger out or feel air your rod is good and your piston is moving.

BUT if you hit something so hard and it sheared your fly wheel key nothing is going to turn.

Look at at your crankshaft while turning the flywheel. if the flywheel turns and the crankshaft doesnt then your key is sheared.

Let us know !!
 
  #7  
Old 09-22-15, 12:15 AM
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The engine should still turn with the flywheel key sheared, and it is is the dowel is moving, but the dowel should move several inches, not slightly. I think you are seeing the valves move, not the piston. I think your engine is blown.
 
  #8  
Old 09-22-15, 05:35 AM
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Boudreaux, The mower and all my notes are next door and I will get the serial number today but I did save a diagram I looked up showing Briggs and Stratton Vertical shaft # range 282700-282799. How can I look at the crankshaft--I thought it was inside the engine? I can look at the pulley below engine? (Sorry if this sounds dumb).
Cheese, I will redo the dowel in spark plug test and see how far whatever moves--but can you see valves through spark plug hole?? I did not remove metal shield around spark plug hole--do they cover up valves? (I'm relying on downloaded engine diagram for how engine is put together). I'll do that today also and report back. Thanks to all. Soon I may have a whole new thread about whether to get old mower fixed buy neighbor's Husqvarna that has been sitting for almost 2 years!
 
  #9  
Old 09-22-15, 10:54 AM
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Yes, on an old 12 hp flathead you can see one of the vlaves through the spark plug hole. The piston and cylinder are to the left side of the plug hole but you can still get a small diameter dowel (pencil sized) in there to check the piston.
 
  #10  
Old 09-22-15, 01:50 PM
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Model 282707 Type 0026-01 Code 960910ZA Ok helpers, here's what I tried (mower is 1/2 mile away thru the woods, hence these delays). First tried to start mower hoping for miracle. Same as before, flywheel spins freely, keeps spinning freely when I stop cranking, unlike normal; engine does not catch. I removed cylinder cover, noted that both valves move I believe normally (my only reference is having adjusted my vw bus valves 30 years ago), piston does not move when I turn flywheel. I pushed piston back by hand, turned flywheel and noted noise as if something metal is loose inside engine. So turning flywheel does not move piston, but pulley below engine turns. Does this mean crankshaft is OK and connecting rod is shot? (I have never seen these items in person, only on diagram, so am operating on very little knowledge, only what I've read) Any chance it is only the flywheel key? Can you tell anything from these symptoms? If flywheel key, could an amateur fix it? Am tempted to get a repair manual and if it shows step by step how to take engine apart might make this a winter project; would be easier though if mower were right here at home.
 
  #11  
Old 09-22-15, 02:02 PM
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Rod is broke

Your rod is broke. If the cover says Power Built or I/C it has a cast iron sleeve and is rebuildable. Those 28 models are beasts. If your crank is still good are your block is not cracked then you have a good chance to rebuild it cheaply.
 
  #12  
Old 09-22-15, 02:22 PM
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Prices

Rod is 30.50
Gasket set is 24.80

Those are OEM Briggs prices.
 
  #13  
Old 09-22-15, 02:22 PM
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yes it is Power Built. I do hate to just junk it because I live in the woods and mowing paths is very rough and the mower in all these 13 years I've had it has been great. Absolutely no maintenance, just new starter parts. The deck is like a tank. The Husqvarna that I might buy from friend is really for mowing lawns, has probably a decent engine but the deck will not likely do well in this rough terrain. Wonder if I could remove the engine myself and take it somewhere for repair? Am concerned with cost of having someone come tow it away. It's quite remote here.
 
  #14  
Old 09-22-15, 02:26 PM
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Those prices are cheap. Could I likely do the job? I know there are youtube videos on how to do it, but unless I can download one to view later, no broadband here to view them. Would a repair manual be detailed enough?
 
  #15  
Old 09-22-15, 03:55 PM
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Video

Here's a link to some detailed vids.

https://youtu.be/DXvgJttmfOs

You can get a service manual in addition to the vids if you want. Hope this helps !!
 
  #16  
Old 09-22-15, 06:09 PM
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It's not the flywheel key, it's blown.
Often there is more damage than just a broken rod. Many times the rod hits the inside of the engine, most of the time behind the starter and it cracks or blows a hole in the block. Sometimes not. Most times the crankshaft has aluminum transfer on it that needs to be removed. Sometimes the piston is damaged, the governor and/or camshaft are damaged, sometimes the cam boss cracks in the block or oil pan. Very often when the engine has run enough to need a rebuild, the balancer bushings are badly worn too. The only thing to do is open it up and see what it needs. If it's good, build it. The engine might be fine and worth repairing or it might be scrap metal. Usually a rod doesn't just break... usually it's because it was low on oil. Low oil conditions wreak havoc on other parts as well.
 
  #17  
Old 09-23-15, 04:12 AM
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Thanks to all. I guess I see the writing on the wall. I probably will try to take it apart little by little just for the learning process and maybe I'll be lucky and it can be repaired.
 
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