Balancing piston weights
Road Master
Joined: Mar 2013
Posts: 817
Likes: 380
From: Central Ohio
are you comparing complete assemblies or just pistons?.. 7+grams seems excessive. I'm used to 2-3 typically unless they're S&S pistons w clearance cut in rear only but, even those are closer than that... you might try measuring both pistons to be sure that one isn't an o.s. while odd, I wouldn't let it stop me. the pistons factor into the balance plot at 60% & that's a total weight divided by 2 ( f&r).. if you feel you must remove material, tread lightly. both cast & forged pistons are processed under pressure for stability sake, removing material from underboss @ w/p can relax the material losing the taper & sizing.. measure both before you start. & after.. if you can't wrap your head around my advice, think about this, the rear rod weighs about 65lbs more than the f-rod. if you feel you need to take corrective action , install lighter piston on the heavier rod...
In your world nothing would have to be weight matched, but this is life. Nothing is perfect, especially castings. Removal of material from an area that literally every engine builder uses (as well as MFGs recommend) causing an issue is fantasy.
Not sure what to make of your "processed under pressure" comment. I suppose machining the dome or valve relief on a piston would affect the ring land concentricity too then...
6th Gear
Joined: Feb 2022
Posts: 12
Likes: 19
From: New Hampshire
Easy on the doom and gloom pal.
In your world nothing would have to be weight matched, but this is life. Nothing is perfect, especially castings. Removal of material from an area that literally every engine builder uses (as well as MFGs recommend) causing an issue is fantasy.
Not sure what to make of your "processed under pressure" comment. I suppose machining the dome or valve relief on a piston would affect the ring land concentricity too then...
In your world nothing would have to be weight matched, but this is life. Nothing is perfect, especially castings. Removal of material from an area that literally every engine builder uses (as well as MFGs recommend) causing an issue is fantasy.
Not sure what to make of your "processed under pressure" comment. I suppose machining the dome or valve relief on a piston would affect the ring land concentricity too then...
i wont make that mistake again..
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Stellar HDF Member
Joined: Jun 2018
Posts: 2,295
Likes: 494
From: WI
Well, the verdict is in.
I had a very close friend of mine run the first 120 mile break in on the new topend. I wouldve done it myself, but I just finished with the neck surgery and I was in a neck brace, I mean I am in a neck brace.
My friend is has owned multiple Harleys throughout the years. He told me that it was one of the smoothest running motors with little to no vibration that hes driven in a Harley Davidson.
So, I guess balancing piston weight was a good idea.
I will pick up this thread in 2023, after I get to put a few thousand miles on the bike next year. Until then
Knowledge is power ..
I had a very close friend of mine run the first 120 mile break in on the new topend. I wouldve done it myself, but I just finished with the neck surgery and I was in a neck brace, I mean I am in a neck brace.
My friend is has owned multiple Harleys throughout the years. He told me that it was one of the smoothest running motors with little to no vibration that hes driven in a Harley Davidson.
So, I guess balancing piston weight was a good idea.
I will pick up this thread in 2023, after I get to put a few thousand miles on the bike next year. Until then
Knowledge is power ..
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