Piston Orientation
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Tourer
Joined: Aug 2014
Posts: 302
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From: Gambrill, MD
Piston Orientation
Hey folks!
As some of you may be aware, I'm refreshing the top end of my 1993 FLHTCU, but sadly I removed both pistons without noting the direction of the arrow on the front cylinder. The service manual says "The arrow on top of the piston points to the front of the engine", but on one of Pacific Mike's YouTube videos of an Evo rebuild, he says that it should point toward the intake valve. He also says that the pockets on the piston are different sizes (the intake being larger), but that's not the case on mine. Well, they're not EXACTLY the same width. At the widest point, one is 1-3/8" and the other is 1-13/32". By the way, the part number of the pistons are 22091-83B.
Any help?
-Dave
As some of you may be aware, I'm refreshing the top end of my 1993 FLHTCU, but sadly I removed both pistons without noting the direction of the arrow on the front cylinder. The service manual says "The arrow on top of the piston points to the front of the engine", but on one of Pacific Mike's YouTube videos of an Evo rebuild, he says that it should point toward the intake valve. He also says that the pockets on the piston are different sizes (the intake being larger), but that's not the case on mine. Well, they're not EXACTLY the same width. At the widest point, one is 1-3/8" and the other is 1-13/32". By the way, the part number of the pistons are 22091-83B.
Any help?
-Dave
Grand HDF Member
Joined: Nov 2009
Posts: 4,315
Likes: 1,663
From: Tampa
I believe it's like this because the wrist pins are slightly off center from the exact center of the OEM piston. Don't quote me though, I seem to remember hearing about it in passing that the wrist pin is just a few thou back from center, which is why the arrow has to point forward. Not sure why if it's true.
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