My parents got me a 2019 Trek 520 for my birthday. A couple weeks later, I re-rode the same century ride on the new bike, a half hour faster, and much more comfortably 😄. That bike, as all our bikes are, was my pride and joy. I got the silver one and got everything to match in silver and blue. Sep 16, 2009 Can anyone help I came across two bitchen bike in swhich I'm restoring 1) is a Robinson with the serial numbers (P)04920942 2) Dyno SY6J000396 I go back and forth between sites trying to figure out how to decide an can't seem to figure out,if ya'll could give it a shot or explain it would be much appreciated. Because if your bike is ever lost or stolen, we can provide you with key information that can help you recover your bicycle quicker and easier. The serial number is located on the underside of your bike. Your product was successfully registered @MONGOOSEBIKES.

Info On Mongoose:
http://www.vintagemongoose.com/
MONGOOSE MOTOMAG: 1975 - 1983
1st gen. gusset by the bottom bracket, a coaster tab but no brake bridge. (Sept'75-Jan'77)
Serial Numbers
(located on the underside of hanger cup/bottom bracket shell):
1975 serial numbers were a hand-stamped five number, individual frame ID. They begin at 10001 and continue until early 1976 when a revised stamp begins to include place of manufacture indicated with the letter 'C' ( for Chatsworth, California) followed by the five number individual frame ID. It then changes again later into 1976 to include place of manufacture/month/year code followed by a five number individual frame ID. Example: CB6 ##### (C=Chatsworth B=February 6=1976). After February 1977, (CB7) the second generation frames appear without the extra gusset between down tube and seat post tube.
2nd gen. removed BB gusset and added brake bridge. (Feb'77-June'79)
3rd gen. removed coaster tab. (July'79-June'81)
4th gen. step down, 2-hole dropouts were added. July '81
SER # Breakdown
For the first year or so it was a hand stamped 4 or 5-digit #. '75 -'76
13054C
17407
The most common # was from '76 - Feb.'81
CA7CL9
31909255406
From '81-'83 they started using this code (it moved around alot)
H159989A3002876
TEAM MONGOOSE 1978 - 1980
There are some Team frames from late '77
full production started in 1978.
they came in Candy Red or Blue over Nickel. 100% Chromoly.
T
CG9
191147

Submitted by Mongoose (View all 77 posts)

Posted 2013-12-03 9:56am

Updated 2015-03-09 1:34am by Hobbes12

5057 views

All bikes¹all have unique serial numbers.

Finding a bicycle serial number

Most bicycles have their serial number engraved beneath their bottom bracket, but sometimes serial numbers are found in other places. Here are some examples of where and what to look for:

Mongoose Bike Serial Decoder Diagram

The bottom bracket (where serial numbers are typically located) is circled.
A serial number on the underside of a bottom bracket.
Another serial number beneath the bottom bracket, aligned parallel to the frame.
Rad Power bikes have their serial number on the head tube. This is on the front of the bike.
Some Schwinn bicycles also have the unique identifying number (their serial number) on the head tube.
A serial number located on a rear dropout. Some BMX bikes and a few Schwinn bicycles place the serial on the rear dropout. On older Schwinns there are numbers stamped on both the drive side and non-drive side rear dropouts; the one on the non-drive side dropout is the serial number.
Some bikes have multiple serial numbers.²When adding a bike to the Index, it's best to enter all the groups of numbers and letters separated by spaces.

Hopefully you can find the serial number on the bicycle you're looking at - email contact@bikeindex.org if you're having trouble.

Mongoose Bike Serial Decoder Chart

Searching serials on Bike Index

Finding bicycles by serial number on Bike Index is a critical part of our functionality. When searching for a serial number, use our serial search bar - it's the second bar on our search form.

We've done a few things to make it more likely that you'll find the bike you're looking for.

How Do I Identify My Mongoose Bike

Certain numbers and letters are difficult or impossible to distinguish between (e.g. 0 and O, S and 5). We treat all these numbers the same way - a search for 005LLL will match a bike with the serial OOS111.
We split bike serials up by spaces and store each separately. If you see multiple numbers on a bicycle - such as in the photo of the Look bike above - try searching for just one of the numbers at a time. Searching for eitherM4106I9CA1 or 200910427-2A will find the bike.
We do close serial matching - bikes with serial numbers that are close to the serial you entered are shown below the matching results under the heading 'Serial Numbers Close to...' - given a search of a serial number with a couple numbers/letters that are different or missing.
We do not currently do partial serial searches. If you search for 1234, you will only find bikes with serial numbers of 1234 and serials close to that - not a bike with serial number of 12345689.

Mongoose Bike Serial Decoder Number

Okay, fine, so maybe there are a few bikes without serial numbers, but this is rare and typical only on hand made bikes or really old bicycles.↩
In this picture 200910427-2A is a manufacturer number and not a serial number. However, to make bikes as easy as possible to find, feel free to enter all numbers you encounter.↩