Help needed identifying front and rear oem pistons

[Adam76]

OK, so I've accidently mixed up my oem 2019 107" barrels and pistons.

I need to know which piston belongs with which cylinder and the only hope I have is that they have different numbers on each piston.

If anyone can tell me which is front and which is rear, it would be greatly appreciated.

Thanks.
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[JSD]

Inlet valve pockets will be bigger than exh ?

[JSD]

Also stock  pistons i believe have offset pin holes favouring the thrust side . EPA thing to keep noise to a minimum. 

[Adam76]

Also stock  pistons i believe have offset pin holes favouring the thrust side . EPA thing to keep noise to a minimum.

OK Thanks I'll check that.  Valve pockets look to be the same size?

[DTTJGlide]

They are the same front & rear, that's what I always thought, but checked the parts catalog to be sure & they list only one part number & you need two if replacing. Are you trying to match them to the cylinders they came out of?

[Adam76]

They are the same front & rear, that's what I always thought, but checked the parts catalog to be sure & they list only one part number & you need two if replacing. Are you trying to match them to the cylinders they came out of?

Yes, there is only the one part number. So they are the same front and rear...
I am simply trying to match them to the cylinders they came from, as I got them mixed up. 

[DTTJGlide]

As poor as MOCO's tolerances are you might make them better, or worse if you switch them

[Adam76]

As poor as MOCO's tolerances are you might make them better, or worse if you switch them

yeah, you're not wrong there!   

[louloupa]

Also stock  pistons i believe have offset pin holes favouring the thrust side . EPA thing to keep noise to a minimum.

KB pistons have offset pin holes .So,there is a front and a rear pistons .They are the only ones like that i know .That's a good solution .   

[JSD]

I see one has GL other GM 

[Ohio HD]

OK, so I've accidently mixed up my oem 2019 107" barrels and pistons.

I need to know which piston belongs with which cylinder and the only hope I have is that they have different numbers on each piston.

If anyone can tell me which is front and which is rear, it would be greatly appreciated.

Thanks.
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Adam, we can see the pistons are both facing towards the front of the bike. Are the valve reliefs the same size and depth? Meaning the two on each piston with the arrow pointing in there direction. If one is deeper and maybe wider, that may tell the tale. The deeper and wider most likely would be the intake reliefs. And be the rear head.  Just trying to understand what is different between them.

[Adam76]

Thanks OHIO, all 4 (actually all of the valve reliefs look to be the same size depth. But I will remeasure them.

There was one piston with a small amount of carbon build up almost in the centre of the piston top, and the other had thicker and more widespread carbon build up. I'm pretty sure from memory the rear piston had the most carbon build up.

[mike jesse]

Are the piston skirts the same front and rear?
If not, the thrust side should give you a clue.

[JSD]

The rear piston if having the relief faces foward

[Dan89flstc]

The OEM pistons are the same part number front and rear.

The front side of the piston is clearly marked with an arrow.

There is no way to tell which piston came from which cylinder, unless you see some witness marks that give you a clue.

Also stock  pistons i believe have offset pin holes favouring the thrust side . EPA thing to keep noise to a minimum.

Engine manufacturers have been offsetting the wrist pin location long before there was an EPA.

[Adam76]

The OEM pistons are the same part number front and rear.

The front side of the piston is clearly marked with an arrow.

There is no way to tell which piston came from which cylinder, unless you see some witness marks that give you a clue.

Also stock  pistons i believe have offset pin holes favouring the thrust side . EPA thing to keep noise to a minimum.

Engine manufacturers have been offsetting the wrist pin location long before there was an EPA.

Thanks Dan, the witness marks in going by are the excesive carbon build up on the rear piston.

As far as off set wrist pins, when test fitting the pistons and cylinders, there didn't seem to be any issues, so maybe I guessed right? The motor turns over easily by hand.

Thanks