I have a 2006 Ultra that I am looking into a big bore kit. I have a friend who knows someone that just sold his bike and it was 2007 Fatboy. The guy did a big bore kit on the bike and has the old cylinders,pistons, and heads for the 96 still in the garage in boxes that the Harley shop had packed them for him when he had the work done. My question is would these work on my 88 TC and give me the big bore that I want? And if so what other things I have to look out for.

 

I don't think the cylinders would fit as a fatboy has a B engine while your ultra has an A engine. Even if it did fit it would be a complete waste of time - there would be minimal difference between your 88" and a stock 96". Get yourself a good 95" kit with high compression pistons - that would be the way to go IMO.

 

The difference between a 88" and a 96" is all in the stroke. That being said, if you did put the 96" cylinders and pistons onto you stock 88" rods, the piston pin height is higher on the piston. Because of that your pistons would be too far down in the bore at TDC and you'd have no compression what so ever. You may be able to use the cylinders but you'd definitely need to get new pistons. There may be other differences that I'm not aware of....I'm sure someone else will chime in.