What am I doing wrong?!?!

[Affordable in Indy]

A customer ran his Craftsman lawn tractor without oil. Of course, the connecting rod broke and the crankshaft is not useable. I bought a new connecting rod and a used crankshaft. I've actually tried two different crankshafts and counterweights. I keep having the same problem. The crankshaft timing gear is not flush with the camshaft (shown in the first pic). When I reinstall the sump cover, it puts pressure on the crankshaft timing gear and the engine won't turn. What am I doing wrong? Maybe the piston is turned the wrong way? Please help!!!

Briggs and Stratton engine 31P677-0912-g5 single cylinder
Connecting Rod part #794122
Crankshaft part # 595339

 

[Rivets]

Are you sure the two crankshafts you tried have the same part number as the one you took out? They may look the same, but have different specs. Also, two different crankshafts were used on that engine, what is your code number?

 

[Scrubcadet10]

Are you sure the two crankshafts you tried have the same part number as the one you took out? They may look the same, but have different specs. Also, two different crankshafts were used on that engine, what is your code number?

120501ZD
the 1 may be a 4.

 

[Affordable in Indy]

The date code is 120501
The second pic shows one of the replacement crankshafts on top and and bad one on the bottom. They both have that 352 number, but I don't know what that number means.

 

[Affordable in Indy]

Oh, yes, you might be right. The 1 might actually be a 4

 

[Rivets]

Most likely the numbers on the crank are casting numbers, so unless you have the casting codes they mean nothing. Are both the slots on the crank, for the timing gear the same? Do the timing gear align at the same point? Do you have a vernier caliper to measure the thrust surfaces to see if the are the same? Sorry for all the questions, but I’m not standing next to you with a strong drink in hand to see what you have. I’m thinking you may not have matching cranks, or the counterbalance does not match.

 

[ILENGINE]

Can we confirm that the crankshafts that you have tried are out of an engine with a date code prior to 120701, since there is the possible chance that the used crankshafts are out of an engine after that date code breakdown and create the issue that you are having

 

[Scrubcadet10]

Briggs & Stratton Part# 797579 which supercedes to 595339 (which is what the OP said he used) is used BEFORE the date code of 12071800 and he has a date code 120501zd... I think 1205 comes before 1207...
Where did you buy the USED crank from? Ebay?

 

[ILENGINE]

Briggs & Stratton Part# 797579 which supercedes to 595339 (which is what the OP said he used) is used BEFORE the date code of 12071800 and he has a date code 120501zd... I think 1205 comes before 1207...
Where did you buy the USED crank from? Ebay?

Makes me wonder if somebody pulled a 596006 but labeled it 595339

 

[StarTech]

The only different between the two crankshafts used that I know of is the flywheel keyway. Briggs change the keyway because flywheel keys being easily sheared. Also the image of the old crankshaft journal doesn't look too bad other than it needs cleaning of the aluminum transfer with Muriatic Acid so that is one option available.

Disconnect the rod any move it out of the way. If the crankshaft now sits lower then the piston rod and piston are incorrectly installed. And check fit of crankshaft afterward by placing the sump cover back on.
It should fully seat without any gaps. Also make sure oil slinger/governor and the counter balance are correctly positioned as either one can jam the engine.