I have a 2003 Fatboy that had a quiet motor, only mods being air cleaner (new S & S) and SE pipes. Ran good but hot and obviously needed tuned.
So I went with an S & S gear drive 509 cam and fuel moto. Cost: almost $2k.
Upon picking up the bike we saw the front head was leaking. So new gaskets for head and base plus some crisping/cleaning of front head and valves. Cost: $500+.
The bike ran really well plus cooler and no hesitation or decal pop. Just good, smooth power and torque.
But less than 400 miles later, there's a gawdawful thrashing coming from down low in the cases and radiating pretty loud up thru the front cylinder. Like I said above, all was typically fairly quiet, mechanically, prior to all this work.
The indie shop pulled the cam cover and said all was well there including cam bearings. They removed the oil filter and cut it in half and found black plastic pieces. They say it's probably the balancer system that has disintegrated and needs the update. Est cost is $1625.
Mileage on the FB is 28,800. The indie says it's somewhat common but not highly so. Friends who should know say the balancer fail (esp at 28.8k miles) is between super rare and non-existent.
Any ideas or comments? Need some help. Badly.
I'm going for a second opinion this week. Trouble is I just can't afford another $1600+ on this bike. Thanks for any helpful thoughts or info.


Gary In Delta

 

My $0.02 would be the cam gear drive is the problem. Most likely too much crank run out for the gear drive. With that many miles would be safer to go with chain drive cams. Have you been doing burnouts? Another thing that is hard on the balancer.

 

Black plastic would be from the chain tensioners for the counterbalance chains. And it does seem to be very rare. Unfortunately, I think you are going into the bottom end. I feel for ya, my counterbalance gear spun on he crank and I had to tear it all the way down. My parts cost alone was $1200 with a welded crank and $350 labor to have the cases split and the bottom end reassembled.

 

If you are splitting the cases, think about replacing the flywheel with a S&S 4.375" stroke. That will bring you up to 96" with the stock bore.

The other option would be to open the bore up to 4.125". With the stock stroke - 107" or with the 4.375" - 117". Of course cam & head work would be required to get the most out of it.