Flywheel nut removal


Old 07-14-09, 05:37 AM
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Join Date: Jul 2009
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Flywheel nut removal

I'm trying to remove the flywheel nut from a 20 HP Briggs & Stratton blown engine on a Craftsman Mower. I tried to keep the wheel from turning by bracing a wrench on the bold head of the transaxial pulley but didn't put too much torque on it for fear of damaging the pully. Several questions here:

The threads aren't reversed on the nut or the transaxial bolt are they?

Do I have to remove the transaxial pully to install a new engine?

Since I'm replacing the whole engine do I even need to remove the flywheel to remove the engine?

Not quite sure how the drive shaft of the engine is connected to the transaxial pully of the mower. Is it simply key and groove, or is there a bolt involved.

Any help would be appreciated.
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Old 07-14-09, 06:26 AM
Join Date: Jun 2009
Location: Virginia, USA
Posts: 45
if it helps

if it's simply a matter of removing the flywheel, i made a fairly simple "flywheel holder", took me under 45 minutes, and used some 3" diameter flat washers, a welder and a drill press -

it also serves to help pull the flywheel off the crankshaft by simply bolting it with the longer bolt set in the pix so it will stand off the flywheel far enough for a 3 leg gear puller to get it's claws under

remember to use washers with a large enough center opening to allow your socket to pass thru

sorry, not familiar with your particular engine, so can't address the other questions but it's a fairly safe assumption the flywheel will have a key of some sort between it and the shaft to keep it from spinning

hope this helps

Old 07-14-09, 08:06 AM
Join Date: Jun 2006
Location: St. Louis
Posts: 2,365
To lock the engine without breaking something, rotate it until it is on the compression stroke, remove the sparkplug, turn the engine back to bottom of the stroke, load the cylinder with small rope(pull rope type)leaving a little hanging out, now when you try to turn the engine it will try to compress the rope and stop, when finished, back the engine off a little and remove the rope. Have a good one. Geo
Old 07-14-09, 03:08 PM
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Thanks for the advise. I think I'll try the nylon rope trick.
Old 07-14-09, 03:40 PM
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If your just removing the engine you needn't remove the flywheel.
You likely will need to remove the pulley underneath, it should have one bolt up through the middle into the crank. It is also keyed but the key is usually fixed.

The output shaft of the replacement engine should also match length and diameter of the old one, IE: the pulley should also fit the replacement engine so belts will match and align properly.
Old 07-14-09, 07:34 PM
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Join Date: Jul 2009
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Since the engine was seized I was able to knock the flywheel nut loose with a socket wrench and rubber mallet.

It looks like I'll need an impact wrench to remove the engine mounting bolts. I was able to loosen one by hand with a socket wrench but the others are just too tight.

I did find a replacement engine that is compatible with my mower.

Do any of you know if the torque specs for the mounting bolts and transaxial pulley will be defined in the new engine's installation manual or do I need to get those from the mower company?
Old 07-14-09, 10:03 PM
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You don't need to remove the flywheel or the transaxle pulley to remove the engine. I assume you're talking about the pulley on the transaxle when you say "transaxial"? You just need to remove the engine pulley, and the mounting bolts and whatever electrical, fuel lines, and cables that connect to the engine.
Old 07-16-09, 12:06 PM
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Join Date: Jul 2009
Posts: 9
Thanks for the help and clarification on the "transaxle" pulley.

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