B+S engine 11hp "synchro balanced" #252707 not firing

Old 10-15-04, 08:15 AM
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B+S engine 11hp "synchro balanced" #252707 not firing

I am stuck as what to do next!!!
Whilst mowing the lawn i heard a horrible crunching noise and the engine completely quit however it would turn over but not fire-up.
upon further inspection i took out the spark plug and front "grill' and turned the fly wheel by hand , the two smaller valves were operating fine but the main cylinder was'nt ! . Could this be a connecting rod problem? and if so how do i go about fixing it without messing up any carb settings . Ihave a parts list so i can order any parts i'll need but i'm not sure how to get inside to to find which part is broken. Any help will be much appreciated

Last edited by Pete.H; 10-15-04 at 08:28 AM.
Old 10-15-04, 09:53 AM
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Whilst you were mowing did you run over or hit anything to cause the "Crunch" ?
When you turn the engine how are you viewing the "valves" and "piston"?
Have you removed the head? (Ref # 5 on the parts list)
Can you turn the engine by hand 3 or 4 complete turns without hearing and "clunks"?........if so....remove the spark plug and put your finger in the hole and try to create a seal, turn the engine (rapidly as you can when feeling resistance, as long as there is no clunks in the previous step) you should feel air trying to push your finger out of the hole. If so continue...if not post back with any new info and we can see where you may be at.....

If you have compresion.....
First thing I would check is the shear key. Remove the shroud from the top of the engine and on top of the flywheel is a nut and a big washer under it. Remove the nut and washer, DO NOT use the cooling fins on the flywheel to hold the flywheel to loosen the nut, hold the pulley and or shaft on the bottom of the engine. With that removed you should be able to see a slot in the shaft and a key, if it sheared it will need replaced. If it is sheared and you need help replacing it post back for help.

Good luck and keep us posted
Old 10-16-04, 02:05 AM
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Hello Pete!

You have a broken connectng rod. Chances are, there is aluminum also smeared on the crankshaft, and possible other damage as well. Removal and disassembly of the engine will be the only way to determine if it is repairable or not unless you see a hole/crack on the side of the block near or behind the starter (most common location for damage). If so, the engine is shot.

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