Originally Posted by
mml373
I'm late to the game but 27.0 is stock for these bikes. I owned an ;'87 and no changes were made except paint/decals for '88. A lot of these older bikes had the seatposts tightened too tightly, or tightened with non-stock seatposts that were smaller, leading the problem you're having.
Yes this bike did get sold (Sadly) due to moving but I did make the 27.0 seat post work on it eventually.