Jr Viper
MSRP $180.00
 Details
Jr Viper

The Jr Viper is a great first time BMX bike for tearing up and down the sidewalk and keeping up with all the other kids on the block. The high tensile steel frame and fork offer worry free durability and the simple single speed drivetrain and doubled up coaster and linear pull rear brakes are easy and safe for young kids to operate.

Highlights

  • High tensile steel frame built to last
  • High tensile steel fork is strong to provide safe handling
  • Single speed drivetrain is simple and reliable
  • Linear pull plus rear coaster brake deliver stopping power
Media Hits
Size Guide
Size 20"
Seat Tube Length ** 250.0mm
Standover Height 0.0mm
Top Tube Length * 487.0mm
Head Tube Length 100.0mm
Head Angle 73.0°
Seat Angle 69.0°
Chain Stay Length 362.0mm
Fork Offset 33.0mm
Stem Length 40.0mm
Handlebar Width 610.0mm
Crank Length 140.0mm
Seat Post Length 280.0mm
* Measured Horizontally ** Measured from Center
Specs
Sizes 20" 
Frame DB Hi-Ten Steel
Fork Hi-Ten steel
Headset Threaded 1"
Cranks 140mm steel 1-piece
Bottom Bracket Looseball
F. Derailleur
R. Derailleur
Shifter
Cogset 18t Cog
Chain KMC Z410 1/2 x 1/8
Brakes Rush linear rear w/ coaster hub
Brake Levers Rush RX2.1
Front Hub 36h steel shell w/ 3/8" axle
Rear Hub 36h steel shell w/ coaster brake, 3/8" axle
Spokes 14g
Rims 36h aluminum, 30mm wide, ano black
Tires Comp III style 20x1.75
Handlebar Hi-ten steel 2-piece 24" wide x 6" rise
Grips DB Icon Grip w/ Nylon End Plug
Stem 1" quill steel base w/ alloy clamp
Seatpost Steel Pillar
Seat DB BMX padded
Colors Green |  Dark Red | 
Extras Owner's manual
Note Specifications Subject to Change
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Unpacking and Assembling Your Diamondback BMX Bike

1

Begin by carefully opening the cardboard bike box. Be aware of the sharp staples that may have been used to secure the box and be mindful not to cut yourself.

For assembly you will need: cutters/scissors; #2 Philips head screwdriver; a 4,5,6mm allen keys.

If for any reason, you do not have the proper tools or are not confident to safely assemble the bike yourself, it is recommended that you take your bike to a local bike shop for assistance or to have them assemble it. We recommend taking all bikes in for a safety check before riding. They may charge you a fee to do so.

Any damage caused by improper assembly is not considered a manufacturer defect and will not be covered under warranty.

2

Once you have the bike box opened:

  1. Remove the saddle and seatpost.
  2. Remove the small parts box.
  3. Remove the bike.

Before proceeding, be sure that all parts and material are now removed from the box.

3

Now that your bike is out of the box, begin removing all of the packing material from the frame and detatching the wheel and handlebar by cutting all zipties that may be holding parts together. Be very careful not to cut any of the bikes brake cables while doing so.

4

Loosen the seat clamp and insert the seatpost into the seat tube. If you have bike grease apply a small amount to the seatpost before inserting it. Finish by using a hex wrench to tighten. Make sure that you have inserted the seatpost past the minimum insertion line (printed or stamped on post near bottom). DO NOT OVERTIGHTEN.

5

It’s now time to install your handlebar to the stem. Begin by making sure the cables are in the correct position. Remove the stem bolts and faceplate, place the bar in the stem and loosely re-secure the faceplate to the stem. Be sure that your cable routing is suitable and that there are no harsh bends or kinks in the cables.

6

Once the handlebar is loosely placed in the stem, make sure that it is positioned symmetrically before tightening the faceplate bolts. When tightening the bolts, tighten them alternately (use and “X” pattern for four bolt systems) and equally to ensure that the faceplate is equally tight on every side. The gap opening between the faceplate and the stem should be equal both on the top and on the bottom.

7

If your bike has a Gyro follow these steps to install your Gyro cable and adjust your brake.

If your bike comes with a straight cable, skip to step 8. First start with routing your upper gyro cable under the cross bar of the handle bar. Now note the cable length, one side will be longer than the other. The longest cable threads into top plate on the non-drive (left) side of the stem. The shorter cable threads into the top plate on the drive (right) side of the stem. Next, push cable narp (balled end of the cable) into the slotted portion of the rotor plate. Repeat this step on the opposing side. Refer to the gyro instructions included with the bike for proper adjustment.

8

Now you can situate your bike in a comfortable working position. If you have a bike stand, that’s your best bet. If you do not have a stand you can flip your bike upside down resting on the seat and handlebars to finish your build.

9

For rear brake, you’ll need to release tension on cable. Start by squeezing brake lever arms together in order to release cable noodle. Next take the rear cable and begin connecting to brake lever. Pull the brake lever to the grip exposing the juncture where the cable enters the lever. Insert the round cable narp (cable end) into lever and guide cable through the designated cable slot on handle. Then place end of cable housing into barrel adjuster. Turn the barrel adjuster so that slots no longer line up with lever slot.

10

You can now mount the front wheel on the fork. For this you’ll need either a 15mm wrench or 19mm wrench depending on the axle size. To start make sure the fork is in the correct position (the thicker metal tab that holds the axle should be facing forward/not towards the rider). Slip the front axel into the fork dropouts. Make sure safety washers are installed property before tightening the front axle nuts.

11

If your bike comes with pegs, you’ll want to install these before installing the axle nuts. You will need a 15mm or 19mm deep socket and extension. Make sure safety washer is installed properly on fork drop out before slipping peg onto axle. Slip the peg onto the axel. Insert axle nut into end of socket and thread by hand until axle nut is snug. Tighten down for safety. Repeat this step for the opposing side and rear peg assembly.

12

Some bikes may arrive without rear brake cable installed. Use the following steps if this applies to your bike.

Pull the break lever to the grip exposing the juncture where the cable enters the lever. Insert the cable narp (cable end) into lever and guide cable through the designated cable slot on handle. Then place end of cable housing into barrel adjuster.

Your Diamondback BMX bike should arrive with brakes adjusted. If your brakes need further adjustment, We recommend taking your bike to your local Diamondback Dealer.

13

Your brake pads may need adjusting once brake is assembled. To do so, grasp brake pad with one hand and loosen brake pad bolt. Align pad to be parallel with rim surface and retighten brake bolt. You do not want the pad to come into contact with the tire.

14

For pedal installation, we recommend applying a small amount of grease to each pedals thread before installing. Next, take the right pedal (this should be indicated by an R on the pedal which can be seen on the end of the spindle or on the axle depending on the pedal) and thread into the drive side crank arm. Tighten by turning your 15mm pedal wrench to the right (clockwise).

Take the left pedal (should be indicated by an “L” on either the end of the spindle or on the axle depending on the pedal), turn the pedal left to tighten (counter clockwise).

Do not force a pedal that will not thread on easily or you can cross thread the crank arm which will result in a damaged product. Damage caused by improper pedal installation will not be covered under warranty.

15

Now it’s time to inflate your tires. Each tire will have a manufacturer’s recommended air pressure (measured in PSI) on the sidewall. Please follow the recommended inflation setting.

16

Last step is to go through the entire bike one more time to make sure that:

  1. every bolt is tight,
  2. your wheels are secured in place,
  3. that your rear brake (if applicable) are functioning properly,
  4. the handle bars are tight and don’t move when you hold the front wheel between your legs and twist them

If for any reason, you do not have the proper tools or are not confident to build a bike yourself, we strongly suggest that you take your bike to a local bike shop for assistance or to have them assemble it. They may charge you a fee to do so.

Any damage caused by improper assembly is not considered a manufacturer defect and will not be covered under warranty.

Make sure to register your bike by simply filling out form found in the back of your owner’s manual and mail it in, OR you can register your bike online at Diamondback’s webpage: here for Diamondback

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