Welcome from south Texas. Trust me, there are a gazillion or more displacement upgrades for the TC88. The MoCo has offered 95" Big Bore kit since the TC88 was introduced; about 10 years ago owners started boring OEM cylinders to 3.938" for a 09" displacement; shortly after that, the MoCo and the aftermarket introduced the 100" kits for the TC88. Worthwhile? Only you can decide that.
Are you considering the $3400 kit with cylinders, pistons, cam plate/pump, lifters and pushrods or just the piston/cylinder kit? Will you be doing the wrenching? Chain or gear drive kit?
Just a few off the cuff things for you to consider.
1. If considering gear drive; crank runout should be checked and if runout is close to or exceeds .003", stick with chain drive.
2. With the increased compression, you will need a progammable ignition to address timing. Stock timinng is a bit advanced and breaking in a new build with advanced timing generates heat and heat is the enemy of an air cooed vtwin.
3. Suggest you look around your area for a tuner that has experience tuning a carbed performance build. After investing that much money in performance upgrades, the new motor shoud be broken in on a dyno if possible. If there is a qualified tuner nearby, a short ride to the dyno won't kill the new build but if a longer drive is necessary, trailer the bike to the dyno. I would discourage you from trying to tune the new, higher compression motor by trial and error rides and plug reading. If you can find a tuner, let him know your motor specs and have him recommend carb jetting and ignition setting for the initial dyno run.
4. The max lift on the '03 models is speced at .510"; some have gotten by with .525" but unless the OEM valve springs are replaced with the later '05 beehive springs, the .585" lift of the 585 cams is a non- starter. I assume the the heads have probably never been removed? If thai is the case, the heads need "refreshed" at a minimum. This could involve replacing valves, guides and springs and will certainly involve general cleaning, carbon removal, new guide seals, valve job and maybe a surgace cut just to true up the contact surface. For the cost of that work, you can send the heads out what is commonly referred to as a "Street" or "Stage I" port job which, considering the displacement of the upgrade would be a good idea.
5. I also assume tha the carb is the OEM CV40? It probably should be rebuilt. There are a couple of easy things you can do to improve the carb performance. Replace the return spring with the lighter spring; drill the vacuum port to 1/8" and replace the A/F adjustment screw with the knurled one; find the parts at CV Performance.com.
6. IIRC correctly, new inner cam bearings are not included in the S&S kit. The INA bearings should be replaced with MoCo or Torrington/Toyo full complment bearings, B148s.
As you can see, if you are doiing the wrenching, you will need to think about "special tools" or work wrounds. Happy to help out.
That's a short list of some up front things I think shoud be considered before you pull the trigger on the S&S kit.
