Friday, December 6, 2013

Atomic 4 engine identification - Serial number and build date

In order to find parts and details on the specific setup of the Atomic 4 it is important to know the date that the engine was manufactured as well as the serial number. Parts guides and tutorials will usually reference one of these numbers.
Example from Manual

Both are located below the breather hose, on the right side of the engine. The build date is the top number and is in the format MMDDYY. The serial number is the 6 digit number directly below.

Atomic 4 serial number and build date
Atomic 4 serial number and build date

[All of the posts associated with this rebuild are available under the search label Atomic 4 Rebuild.]


  1. That is not the location for the serial number. I have the exact same number on my engine. The correct location is under the oil fill on a flat area on the front of the motor. 6 digits.

  2. Mine shows on a metalic label on the flywheel cover.It says Medalist Universal Motors then the Atomic 4 logo, Oshkosh, WI then below that is Serial # (6 digits) and model # 5101. Below that it says Firing order 1,2,4,3 and engine rotation to the left and a timing mark sign.


I appreciate your feedback, comments and other helpful input.