I have a 1985 Softail 4 speed chain drive electric start (no kicker) with a 96" S&S SuperStock motor. I love the bike! It runs great, has tons of power and we just did a custom old school paint job so it looks bitchin too. I have had the bike for almost a year and put about 1500 miles on it (down for 3 months during the painting process).
Now the problem. The trans has started leaking oil around the mainshaft behind the countershaft sprocket. It got worse and worse. I put in a new seal and o-ring. Now it doesn't leak while sitting but as soon as I've ridden a few minutes it pours out! We put it up on a stand and ran it. It seems to leak heavier when the power is on. A local independent shop has suggested that the 4 speed just isn't up to the power of the S&S 96". He says that leakage is the sign that the 96" is "workin' that ole 4 speed to death". He says I should rebuild it but he isn't sure how long it will last before the leakage problem returns. The trans operates normally otherwise.
My Question: Is it possible to rebuild the 4 speed and beef it up in the process so that it can handle the 96"? I would rather keep the 4 speed instead of converting to a newer 5 or 6 speed. If it is possible to beef it up, who should I take it to - or what needs to be done that is different from a standard rebuild? I gotta believe there is someone out there who ran hard with a 4 speed in the old days (before 5 and 6 speeds) and knows just how to make them live.