So, I have a 89 FXSTC and a 98 FLSTF.
Both bikes run well but I've noticed the 89 seems to be balanced differently and a little rougher. Is it just my imagination?

 

Probably... tho I would expect the older '89 to be balanced at a Different factor from the newer one .. simply moves the "sweet spot"
Rumor is that all of the Softail line was continuously Balanced, while the Rubber mounted models were Not Balanced, at least Carefully..
Just Rumor tho far as I know..
I know certainly, that someone who knows exactly what they are doing, and performs the Flywheel balancing meticulously... produces a much Nicer Engine..

I doubt the Factory has a One Man Balancing Operation...

 

It would be interesting to see some inside info about how the factory balanced and trued the flywheels on our bikes over the years. I wouldn't be surprised if by 1996 model year production, they had some sort of nifty automatic balancer that spun them up and automatically drilled out what was necessary, all computer controlled.

Or maybe they didn't do any of that and its just luck of the draw what sort of motor you got.

 

If they have "auto Balancing"... I pray it is better than what S&S is Using!!!
Only my [ex] Partner Balances my Flywheels... Tho I can... he is Much more meticulous than I am.....

 

I saw a vid from Kenny Tatro where he pulled apart some brand new S&S wheels and put them through his balance process. They were way, way off from the factory.

 

Two things that may explain why they seem different. Later Evos AFAIK have beefed up crank-cases, which may help damp down vibration, but in addition, during those nine years the MoCo may have done some development work to improve engine balance and hence ride quality.

 

And from what I have heard... they have Not improved... I ran lots of S&S stuff... but again... only Mine or my Partners Flywheel assemblies.

 

I paid a few hundred to have Darkhorse incorporate a balancing to my Evo Sportster 88" project back a few years ago.

It still vibrated my teeth out on the highway.

 

Don't know no dark horse... but... reinforces my resolution to only use what I know...If mine vibrated unacceptably... I would rethink the Factor... knowing all else is Good....

 

Darkhorse is THE authority on all facets of Harley crankshaft work. You need ta learn yo-self!

You wanna learn more? Google "Harley secondary balance" and see why the 45 degree single crankpin engine cannot be perfectly balanced under any circumstances (other than counterbalancing weights).