karmantra

Picked up a 19" Sekai 2400 Limited for $10--beautiful pewter gray with Tange Champion butted tubing, 12 speed with Sugino GT crank, Suntour AR & ARX derailleurs, Diacompe AC 500 brakes (love that high pivot arm!), 27" Arraya wheels with Specialized Touring tires. Funky high handlebars, but I'll put drop bars on it. Problem is that someone did the old 'zigzag' to the seatpost, apparently didn't grease it at one time, to the point that I can't read the size of the post. I went to Sheldon's site, but nothing was listed--anyone have the seatpost diameter for a Sekai 2400? I also would like to date it. Thanks!

T-Mar

The AR/ARx derailleurs suggest 1981-1986. Given that, I went back through my literature and found Sekai 2400 specs for 1984 and 1985. Both used AR/Arx derailleurs, Sugino cranks, Dia-Compe 500 brakes and Araya rims, though the 1984 used a triple crankset and Tange Mangaloy, while the 1985 used a double crankset and Tange 900 tubeset. What's interesting is that the 1984 specs actually list the seat post diameter, which was 26.4 mm. This is slightly smaller than the 26.8mm which is normally found on frames made with Tange Champion tubesets.

To be sure, I'd take the bicycle to a good LBS. They may have a graduated gauge to measure the inner diameter of the seat tube. Lacking that they should have a micrometer or precision calipers to measure the diameter of the seat post in an un-marred section. However, the problem with the latter, is that the marring may be due to an oversize post and not just the lack of greasing before insertion. Of course they could always use the trial and error method, starting off with a small diameter post and incrementally increasing the size, until they found the correct one.

If there is no LBS around and you do not have access to micrometers or calipers, you can always tightly wrap a strip of paper around the post and mark where it overlaps with a sharp pencil. Unwrap the paper and measure the distance from the end to the pencil mark. Divide the measurement (post circumference) by 3.14 to get the diameter. Repeat a few times, to ensure the results are consistent. Using this method, you should be able to measure the circumference within 0.5 mm which should provide the diameter within 0.2 mm. I've tried this method using a few posts and have always been within 0.2mm of the marked size.

Regarding the bicycle's age, refer to the Vintage-Trek website for decyophering the date codes that can be found on many of the components. Good luck!

bellathebug1

I have come across a sekai 2400 racing bike with ramshead handle bars and pedal foot holders. Do you know the value of this type of bike in good shape?? please let me know anything you know. thanks ab

T-Mar

The mid-1980s Sekai 2400 as described in the original post was $250.00 US. Value can vary substantially depending upon the local market conditions, as well as the cosmetic and mechanical condition of the bicycle.