Originally Posted by alk
looks like yellowjersey used to have decals, but they are out of the ones for the 5000 model.
http://www.yellowjersey.org/sekai.html
there's a 1975 sekai catalog there. it says the 5000 from that year is made from "Tange Professional 0.6x0.3 double butted Cr-moly throughout" and that it weighs in the low 4 pound range with the headset. that is an obscenely thin tubing diameter, and an obscenely light frame. with that in mind that it has received some dents is unsurprising.
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seriously, 0.6x0.3 tubes! that's thinner than ishiwata 015, which has a maximum recommended rider weight of 125 pounds.
http://www.desperadocycles.com/Tubin...per_Tubing.htm
now yours may be a different year and have different tubing. still, i would suggest treating it nicely.
Thanks for the feedback all. I’m really enjoying restoring and riding a great old bike that almost got thrown away. I am doing my best to treat it nicely.
Re decals: If I really wanted to, I could cut-and-paste the downtube decals that Yellow Jersey has in stock, to create "Sekai 5000". But I kind of like the naked/stealth look. Nobody seems to have heard of Sekai anyway, so it's not like decals would add cachet like if it was a Paramount or something. Maybe I'll reconsider and add decals if I ever get the bike repainted and clear-coated.
Re the tubing: don't know the exact model year, so I don't know if it's the Tange Professional 0.6x0.3 tubing shown in the 1975 catalog. Between the Yellow Jersey owner's recollection and some very helpful PM input from T-Mar, best guess is it’s a 1977 frame. The BB is stamped "CHAMPION" and there is no serial number.
But the tubing is definitely very thin. Squeeze one of the main tubes with thumb and index finger, and it bends in a little bit. The top-tube and seat-tube dents are probably from repair-stand clamping. First (and last) time I brought the bike in for repair, they said "oh don't worry, we'll use this special gentle clamp on the seat tube, there's no way it can cause a dent." But sure enough it did ... and from now on I’ll wrench the bike myself at home, thank you.
Also the rear dropouts are Campagnolo replacements - maybe that part of the frame was damaged worse in a repair stand. That could also explain the lack of serial number, which might have been on an original rear dropout.
I’m a pretty skinny guy, but no 125 pounder … hopefully this bike can handle a little more than that!