Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties Flywheel end play

Flywheel end play

Post Sun Aug 19, 2018 6:45 am

Posts: 98
Flywheel end play is spec'd at .010-.014, or .012-.014, depending on which manual is used. This spec seems a bit wide to me. Is the wide endplay to account for crank flexing, or something else?

Post Sun Aug 19, 2018 12:56 pm

Posts: 3472
Location: Central Illinois, USA
I can think of a bunch of reasons, Larry!

But oiling would top the list...


Post Sun Aug 19, 2018 6:16 pm

Posts: 98
Both bearing races are grooved to allow oil to reach the rollers. In addition, the drive side has channels cast in and a hole bored through to the race for oil supply; yet the factory thought that wasn't enough. I find that interesting. What are the other reasons?Image

Post Sun Aug 19, 2018 9:16 pm

Posts: 1368
Location: Ojo Caliente,NM,USA
Those two openings let oil in how do you suppose it gets out? Right it slings out in that clearance you mentioned. If the oil doesn't flow freely it stays in the bearing and stirs creating friction and heat. It is also that large because the shape of a crank assy causes it to expand more linearly whereas as a case because of its shape (even though aluminum expands more than steel) expands less on that axis than the crank. It wouldn't hurt my feelings if one was .017.

Post Mon Aug 20, 2018 6:28 am

Posts: 98
That makes sense.

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