This is the original crankset still on my 1977 2500 Grandtour.
https://c1.staticflickr.com/1/561/31...f66f50f4_c.jpg

Sekai 4000 Serial number
 

I have a Sekai 4000 Professional which I purchased new as a frameset in 1983. The serial # is M8M 22913. It was black when new, has Shimano SF vertical dropouts, Champion #2 Tubing, Heart cutout lugs, brake bridge diamond reinforcements and a full wraparound seat stay attachment. It had the green Champion tubing sticker. Is this a 1978 Miki produced frame?

Retrofaction, the odds of it not being Miki are negligible, given that Miki was a known manufactrer of these frames and the serial number format is consistent with Miki. Unless you made a mistake on the serial number it was manufactured in 1978.

Picked up a new to me Sekai 2500 Grandtour today! It's pretty crusty, paint is in the worst shape. I road a lower model Sekai throughout college that I saved from a dumpster so excited to fix this one up.

Serial Number is YOL8103.

Says it's Tange Peerless, which I've never heard of.

I'm a noob and don't know what Seat post OD means, lol. It has stem Shimano shifters, a rear rack, SunTour VX front and rear derailleurs, Dia-Compe brakes and levers, and a super maxy crank with a 52/40.

Tange Peerless is new to me, too. The serial number indicates it was manufactured in 1980 by Yamaguchi, though it should be a 1981 model. I don't believe there are any in the database from the very early 1980s. The very late 1970s versions used Tange #101, while circa 1983 they were Tange #2 . Consequently, I'm also interested in the clue from the seat post outer diameter, which is typically stamped somewhere below the insertion mark, format 26.x, where x is an even number.

Thanks T-Mar, I found it! The seat post says Max.HT 26.2 and then L-80. The Peerless stamp says high tensile double butted.

The post size is consistent with the double butted hi-tensile set and the post's date code corroborates a 1981 model manufactured in late 1980. It appears that Tange renamed their #101 double butted hi-tensile tubeset. That's good to know. I'd appreciate a picture of the tubeset decal.

I certainly will after I can get to 10 posts, lol!

T-Mar any further thoughts on whether this Miki built frame is a Sekai?

Folks: I am a newbie on this forum. After storing my late brother-in-law's Sekai I am getting it cleaned up to ride and trying to understand what I have. Serial Y0L9353 with a made in Japan sticker. As best I can translate the serial number from this thread it is somewhere in the 1980-85 range. Can anyone help me understand more clearly how to decipher the serial number code?

Your frame was manufactured in 1980 by Yamaguchi of Japan. It may be late enough in the year to be a 1981 model.

Thanks T-Mar. Just what I was looking for.

Any deciphering? Y0L9353 "Year / ?? / ?? / production count?"

Thanks, Highpockets.

I am in middle of cleaning up my Sekai GT2700 and I believe the seatpost tube diameter that came with is not the right size.
Does anyone know what is the right size of the seatpost?

https://cimg1.ibsrv.net/gimg/bikefor...2c11f9f927.jpg

Hi. may you help me identify my friend's serial number frame
1. located on a straight bottom bracket and there are 2 ellipse holes Y5M85031285 / YSM85031285
and is on the top right head tube E5 E5
and head tube left top down 73 61
then there is a hole holder for the road bike shifters left and right on the frame
https://cimg3.ibsrv.net/gimg/bikefor...cc7e009328.png

example of the shape of a bottom bracket hole

2.there is a straight bottom bracket M23751
there are 3 small round holes forming a triangle. and there are also serials in the drop-out chainstay but I don't know. then the road bike shift holder left and right are bolt pivots
its all have doible bidon

Is this one of the sekai or the other
Please help. Thanks

Hi, I've just picked up a rusty 2500 serial number 365450. I'll post more details later.

Sekai 2500 Grandtour
18 speed
Colour: Dark Red
Frame: 21”.
Front & Rear Derailleur: Suntour Mountech
DT Shifters: Suntour
Crankset: Sugino GT
Chainrings x 3
Pedals: MKS GR8 (Japan)
Hubs: Suzue
Rims: 27” No identifying labels but assumed to be original
Brakes: Dia Compe
Serial No. 365450
Made in Japan sticker

Interestingly the serial number is very close to dougb’s 2500 in post #285. Identical colour & decals so may be part of same batch.

Based on the Mountech derailleurs and serial number, its likely a 1983 model or a 1984 model manufactured in late 1983.

Thanks T-Mar. Any idea when they finally ceased production on this particular model?

1977 2500 Grandtour 64cm
 

Figured I'd post this before I sell it.

Picked up this one and another Sekai off craigslist back in the day. Sold the other one right away for more than I paid for the pair but kept this one.

Figured I'd post it before it dissapears

This Sekai 2500 Grandtour 64cm with 27in tires. Chrome moly, double butt, hi-tensile construction, Raleigh handlebars, SunTour Cyclone gearing, brakes,etc.


Sekai Grandtour 2500
64cm (25.25")
58.5cm top tube
27 in wheels
27 x 1 3/8 Kenda tires
Suntour AR LI derailer
Suntour Cyclone front derailer
Suntour Power shifters
Moxy cranks
Sekai seat (not so great condition)
Raleigh headset
Raleigh handlebars
Dia-Compe break levers
Dia-Compe front and rear brakes

Serial# 77G90258

I cant post photos as I dont have 10 points I guess.

https://cimg6.ibsrv.net/gimg/bikefor...dabdb79077.jpg
https://cimg4.ibsrv.net/gimg/bikefor...f58c13c9c1.jpg
https://cimg9.ibsrv.net/gimg/bikefor...dcdb52729b.jpg
https://cimg7.ibsrv.net/gimg/bikefor...d1a0d48966.jpg
https://cimg5.ibsrv.net/gimg/bikefor...fc4d4d24c7.jpg
https://cimg8.ibsrv.net/gimg/bikefor...0fc561b5ce.jpg
https://cimg3.ibsrv.net/gimg/bikefor...bddb18d521.jpg
https://cimg9.ibsrv.net/gimg/bikefor...7c4bab750a.jpg
https://cimg6.ibsrv.net/gimg/bikefor...b296ba602f.jpg
https://cimg5.ibsrv.net/gimg/bikefor...34f364865c.jpg
Hi All - I'm new to this forum and thread. I recently found what I hope was a solid pick up off craigslist - a Sekai of some type for $60. This is my first rebuild and I'm hoping to get some help from this thread. I can't identify exactly the make and year based on the info earlier posted - but I've taken the bike apart and hope the info I'm sharing will be enough for someone to help me. I've also started to collect parts to clean up/tune up the bike. New brake wires, new chain, new bar tape. I'd like to consider converting the Barcon shifters to downtube or stem...is that dumb? I'm just going to use this bike to cruise around my city, nothing crazy, no real long rides. Any and all help/advice is welcome! I want to post picture but i don't have 10 posts yet...

Frame Sekai 2000 Special? Not sure!
Serial # K8H03368
Handlebars Sakae Custom
Shifters Suntour Ratcheting Powerthumb Barcon Shifters
Front Deraileur Suntour Compe V
Rear Deraileur Shimano Crane GS DR-102
Cassette Maeda (suntour) Perfect 8.8.8 PF 5 speed.
Crankset/Arm Sugino Maxy 165 Arm 52
Brakes Silver Dia-Compe 610
Brake levers Weinmann Red Dot Type 500
Bearings Suzue SATN 0.5
Rims Ukai 27"x1.25" W/O LA
Pedals Lyotard 136R
Saddle Selle Italia Touring
Frame Pump Primus

It has obviously be frankenbiked to some extent with the Lyotard pedals, Weinmann levers and Crane derailleur being replacements. This complicates identification. Normally, I would say it's from 1978 based on the serial number. However, the Compe V front derailleur, if OEM, suggests something earlier and the serial number may utilize the Japanese Imperial calendar and could represent 1973, with the bicycle being a 1973 or 1974 model. This is supported by a Maeda freewheel with a PF date code, representing June 1973. Pending further information it's sounding like a 1974 Sekai 2000 Special. Is there a decal mentioning tubeset type? Also, please check for date codes on the back of the crankarms. I'm expecting something like 48-x(x), where 'x(x)' is a single or double numeral.

Models list updated
Known year to serials list updated
Links added for Don Gillies photo collection as well as catalog scans added to thread
Added info blurb from T-mar to initial post

Sekai serial # Help
 

I've recently purchased serial number K9AU3795 . I'm thinking USA market 1979 ? The bike is silver with a Sugino Mighty Competition 2 chainwheel crankset. The rear is a five speed. It has aluminum 27 x 1 1/4 ARAYA wheels. A sticker on the seat tube saysG3445 seamless hi tensil steel throughout. It has Suntour bar end shifters and Suntour Cyclone deraillers front and rear. Suzue hubs. Maeda Industries Perfect freewheel?Also the front fork has a sticker that says SKV. The model sticker is gone so I'm not sure what I have here. Any help would be appreciated. Thanks