Hi everyone! I bought an old Sekai at a garage sale years ago, and have ridden it on and off since then (2010). I love the bike, but it's needing some significant cleanup and maintenance soon. I was debating restoring it, doing minimal maintenance to keep it riding, or sell. I'd love to know more about the bike, and if it is considered one of the nicer/important models. The serial number is on two lines:
DS70
514065

Other identifying features are:
SAKAE SX crank
52 tooth large gear marked "SA 307", 42 tooth small gear marked "SA 362"
HTI A19 metal pedals
Shimano front & rear derailurs (12 speed)
Shimano Downtube shifters marked "SL-S434" and "light action SIS"
Joytech rear quick release axle
Sachs front quick release axle
Dia-Compe brakes
Leech brake handles (possibly not original? They're plastic)
Araya wheels, aluminum, 27" x 1.25"
26.3mm diameter seatpost

Pictures are in a Google Photos folder here: photos.app.goo.gl/JvsjSU9qPQcg1XeVA

Any help or pointers would be greatly appreciated, thanks!

Also you can't post a pic, we have to work to can do this

Given the description so far, no it's not one of the more desirable/more valuable models. Shimano Light Action was at the lower end of their product line. Somewhat smallish seat post OD (the better the model, the larger the post diameter). Shimano, Dia Compe, and others made a wide variety of components from really basic to really great and everything in between. This is why you will see bikes at Walmart advertised as "Shimano".


Serial number at best just indicates year bike was made.

Identifying features: tubing decal on frame describing tubing used to make the bike. Model of components. Date code of components. Seat post outside diameter (you got that). Is RD claw mount or attached directly to frame? Are seat post and handlebars steel or aluminum? Are chain rings steel or aluminum (magnet will tell you). Pedals are super easy to change, so in 30+ year old bike, they likely are not original.

Finally, your location can have a major impact on value. A bike could be worth $25 in one town, and could be worth $175 in another town.

True restoration is a guaranteed money losing proposition. Doing basic maintenance may give you a slight return. Doing basic maintenance and continuing to enjoy riding it will give you the maximum return!!

You can read several recent threads where many of us lament the downturn in value of vintage bikes. In my area, everything but the very best has dropped about 50%. The days of refurbishing a middle of the road vintage bike and making a decent return for your investment is over. I now save my time for really special bikes or for parts. The better parts can still be financially rewarding.

Thanks for the help! That's about what I was guessing. I think the best option is to do whatever I want to it to make it a bike I enjoy riding. And then ride the heck out of it. Right now it is my daily commuter to work. I suppose I just wanted to make sure I wouldn't be breaking anyone's heart by modifying a "rare vintage piece of history" with a few modern components, and foregoing a proper restoration.

Had trouble with pictures before, trying a different computer this time. Oh and I realized I mis-represented the speeds earlier out of ignorance. It is a 6-speed bike, or 6x2. 6 cogs, and 2 chainrings. You get the idea

To answer a few of your great questions:
1. There are no tubing decals left on the frame, just the "Sekai" label on the front. No help, I know.
2. Rear Derailleur is "Integral Mount", bolted directly to the frame.
3. Handlebars and chainrings are steel
4. Seatpost and cranks are aluminum

Still having trouble with the pictures, not sure why it's not letting me attach them, sorry! I'm probably too new to the forum.

Sekai Bicycle Database

...I got to your photos using the link you posted. Relax, it's not some great piece of cycling history. Just do what you want to make it pleasing to ride.

Pic & link assist:

+1. I looks good, though. I like it. Well-made, sporty geometry, nice paint, great color, fender eyelets. In short, a very nice versatile bike.