Flywheel casting dates

Information on the identification and numbering of frame, motor belly, transmission and other parts
Post Reply
Posts: 1556
Joined: Wed Jul 07, 2010 4:28 am
Bikes: 1950Panhead
Location: USA

Flywheel casting dates


Post by 1950Panhead » Thu Apr 26, 2012 8:42 pm

Flywheel on left has larger "150-403", has a 2 above MC, has month A above date.
Please post 41-54 flywheel format and dates.
You do not have the required permissions to view the files attached to this post.

Posts: 814
Joined: Tue Aug 03, 2010 7:10 pm
Bikes: 2008 96" Fat Boy TC
Location: New York

Re: Flywheel casting dates


Post by kitabel » Thu Apr 26, 2012 10:58 pm

The large numbers are not dates, they only indirectly identify the casting as to purpose and lineage.
All early flywheels are "150-" regardless of engine type.
All flywheels first introduced in 1940 end in "40X", where X is blank (150-40) for the first flywheel, then a number is added in the 3rd position as many times as needed to cover new flywheels for 1940: 150-401, etc.
Left and right are not odd & even, and may not be sequential.
150-40 identifies all early OHV big twin wheels with 8.50" OD and 1.00" shaft tapers, regardless of stroke length.
150-40X right flywheels are also used in somewhat later engines.
Around 1955 the numbering system changed, and on newly introduced wheels the entire part number appears on the flywheels, such as 23933-55.

Other common castings: 150-30 are VL, 150-32 are early 45, 150-35 are early EL or 1935-36 VLH, 150-37 are later 45 or UL

Post Reply

Return to “Identification”