Cobra Motorcycle FAQ

This is where you will find the most frequently asked questions posted in our forum.

CobraTalk.com » Cobramini.com
COBRA FAQ

• What is the difference in the A-B and C-D grades for pistons and cylinders?

• What should my Gear Ratio be for Mud, Sand, Hills, Hard Pack, or a Novice rider (throttle blipper)?

• What is the fork upgrade for the 2006 King? Do I have the new Fork Updgrade? How do I get it?

• How do I test my Stator?
 
What is the difference in the A-B and C-D grades for pistons and cylinders?

Engines are assembled to very tight specifications, and all manufacturers of high performance race engines grade pistons and cylinders to meet these requirements. And, to confirm a key point: THERE IS NO PERFORMANCE DIFFERENCE BETWEEN ONE GRADE OF PISTON/CYLINDER AND ANOTHER. To illustrate, below is some data from our King 50 piston:

Grade Nominal Diameter Range

A-B 39.000 - 39.010mm
C-D 39.011 - 39.020mm

So the difference in engine displacement from an engine that is at the very bottom of the A-B scale to the very top of the C-D scale is .05cc (five one hundredths of a cc). Not enough to make any noticeable difference on the track or dyno or anywhere else.

On the other hand, if you have a piston that doesn’t fit your cylinder properly, there WILL be a noticeable difference in performance through increased friction or decreased sealing of the piston rings.

Back to top
 
What should my Gear Ratio be for Mud, Sand, Hills, Hard Pack, or a Novice rider (throttle blipper)?

For a bike with a centrifugal clutch, it’s better to be geared too low than too high.
What happens with improper gearing?

  • Poor performance
  • Not enough top end speed
  • No snap
  • Over heat clutch
  • Premature failure of engine seals, bearings, & electronics
  • High clutch wear.

Condition Gear Taller Gear Lower   Front Sprocket Rear Sprocket Gear Ratio
Mud   ∨ ∨     15 33 2.20
Sand   ∨     15 34 2.27
Hills   ∨     15 35 2.33
Hard Pack ∧     14   33 2.36
Throttle Blipper (novice)* ∧       15 36 2.40
*It may be helpful to set up the clutch to hit early for smooth power delivery   14   34 2.43
      15 37 2.47
Front Sprocket Rear Sprocket Gear Ratio   14   35 2.50
10   37 3.70     15 38 2.53
  11 41 3.73 13     33 2.54
10   38 3.80   14   36 2.57
  11 42 3.82     15 39 2.60
10   39 3.90 13     34 2.62
  11 43 3.91   14   37 2.64
10   40 4.00     15 40 2.67
  11 44 4.00 13     35 2.69
  11 45 4.09   14   38 2.71
10   41 4.10     15 41 2.73
  11 46 4.18 13     36 2.77
10   42 4.20   14   39 2.79
10   43 4.30     15 42 2.80
10   44 4.40 13     37 2.85
10   45 4.50   14   40 2.86
10   46 4.60 13     38 2.92
    14   41 2.93
13     39 3.00
  14   42 3.00
13     40 3.08
13     41 3.15
13     42 3.23

 

Back to top
 
What is the fork upgrade for the 2006 King? Do I have the new Fork Updgrade? How do I get it?

Anything shipped after Jan 25th 2006 has the new fork upgrade, cartridge tubes, straight from the factory.

As part of Cobra's ongoing effort to make sure Cobra customers have the best performing motorcycles on the track, they are offering an upgrade to the 2006 King front fork. This upgrade is in the form of a new cartridge tube. The new part improves fork action by ensuring the alignment of the cartridge system under heavy loads, and by making the fork's action more progressive throughout the compression stroke. The parts for this upgrade will be supplied free of charge from Cobra. All 2006 King customers will be given the option of upgrading their fork directly through Cobra or through an approved dealer or suspension shop as part of your normal fork maintenance routine. Please have your VIN ready and call Cobra to schedule your upgrade (330-549-9600).

Back to top
 
How do I test my stator ?

Remove the radiator cover(s) and find where your ignition coil(2) and stator(1) connect.
Un-plug the Coil plug(2) from the Stator plug(1).


Remove the red plastic insert by pulling back on the two small clips(3)
Withe the insert removed you now have access to the contacts.
Note the light blue wire(4) and the violet wire(5) and the contacts directly in front.
These are the two contacts you will use to test the stator.


Set your meter to the Ohms ' Ω' setting(6).
Attach your meter leads to the 2 contacts in line with the blue and violet wires(8)
The resistance(7) should not be below 87. Anything below that would mean a bad stator.
You should not get any reading between the black wire(9) and any others.

Back to top
 

Back to CobraTalk » Cobra FAQ