I know I should have probably thought through this a little bit better, but I "think" I want to go to a 122 for alil mo power on my Low Rider S. I already have the stage 2 power kit installed which is a different cam from the 122 kit.
Anyone here added the the larger heads with forged pistons and rings? If so, have any numbers? My apologies ahead of time if there was an existing thread for this set up and I missed it.

 

You can buy the cylinders and pistons from the 122 kit separately. That is all you need. The power cam will be fine.
Harley may not have a tune for this combination as the cam is different than the full kit with the torque cam.
Changing heads will not give any significant benefit.

 

Thanks for the info, much appreciated!! What would be the best power for dollar option after adding the the cam?

 

You're pretty much into diminishing returns at this point.

Enjoy the bike.

 

You are a true MVP, thanks

 

Thread with some numbers

I was impressed with the gains made by the kit, but I went from stock to the 122 after 960 miles. Some of what I discuss there is moot as there are now aftermarket tuners available for the 2021’s - I’m currently waiting on tuner and cam to see where that and a dyno tune take me.

Good luck with your build.

 

Why just do it 131 ?????

 

As the pistons get bigger in diameter, the piston skirts are shortened so they don't hit each other when the crank pin has them both near the bottom of their strokes.

Short skirts allow the pistons to rock more in the bores and there is less surface area to react side loads. The engine wears out faster as a result.

I think the 122 is the right size for a good compromise of engine life and power.

 

That is an excellent point. You also have to start taking other parts of the drive train into consideration too. Clutch, compensator, trans and etc. With my stage 2 114 all I did was upgrade the clutch springs for $25.

 

This is exactly why I went with the 122 for my LRS, I've had some big motor Harley's in the past that were awesome.....but I was constantly replacing things that they wore out or broke. I was pretty impressed with the 122 kit, sure I could've got something that made more power but having done that in the past, I'm more than content now with the 122 and the security knowing it's under warranty.