I have a 80" 1989 FXRT, GREAT BIKE, with a noise problem with start up. I think it may be piston slap. It has S&S cases, cam, pistons, E carb. and heads. Single fire ignition and coil. Thunderheader 2 into 1, puts out 90 hp and 87 lbs of torque. Stock crank and connecting rods. If I have to take it down what would be a good cylinder bore to go with to increase the cubic "??

 

You can go to the 3-5/8 bore Axtell iron cylinders or the S&S aluminum cylinders and retain your through studs or go to ductile iron 3-13/16" cylinders with base studs and head bolts and outside oil return lines. The 89 cases are stronger than the 90 and up cases, they are the last year before the factory cheapened up the case castings.

 

With the S&S cases you have, then a 3 13/16" cylinder kit would be a shoe-in, to bring it to 97". Have a late-90's FX in now doing the same to it.
With minor cylinder head work, and something as simple as an EV-27 or a Wood 6 cam, 95-100 hp, and 105-110 ft/lbs is a piece of cake.
Strong power from off idle-out.
Scott

 

go with the 3.812 axtell stuff,built alot of 3.812 evo`s & run the on my 106" softail

 

You'll also want to re-balance the crank, as the 3 13/16" pistons/pins/rings/etc, carry a higher gram weight than the OEM's.
Do that, bore the cases, mild head work and a mild (or bigger) cam, and you'll be rippin'!!!
I will also say that you'll be SMOKING, you bud's, with most T/C builds.
Scott

 

The bike has S&S Super stock heads and a 561 lift cam, Super E carb (hot set-up), 10.5 comp. pistons, S&S, But still has the stock cylinders, rods, and crankshaft, I know to rebalance the crank but, will it hold and the other OEM parts?

 

What we have done in the past is to weld/machine/blend the chambers into a bathtub configuration(those heads have that CNC'd chamber to match the pistons). Works like a champ.
The 561 will work just fine as long as the compression is set for it.
Scott