SP125 Limited

22 Walker Wood,  Baildon,  Shipley,  West Yorkshire,  BD17 5BE,  England

Telephone 01274 583231      steve@sp125racing.com      Mobile 07738 626165
 
 

www.sp125racing.com
 
RS250 - 16 settings Ignition Curve Changer
 
Change your ignition-timing map the easy way
 

 

  

 

 

 

 

 (Shown with outer cover removed)
The Curve Changer will alter and improve your ignition map profile.
 
The reason the curve changer works is that the standard ignition is a generalisation for all
... it is not too difficult to tune, suitable for all fuels, all gearing, etc.
 
After designing a programmable ignition for the RS250, the largest requirement was to increase the drive area
advance, without then causing the over rev to 'brick wall' do to its increased compression effect.
A simpler lower cost unit could provide this requirement. … The curve changer
 
The largest advantage is in the increase in the spread of power.
 
The 16 settings unit is an enhancement of the standard RS250 Curve Changer.
It allows a switch selectable range of map alteration.
 
By using fixed switch values the result is accurate and repeatable.
 
The switch has 16 positions 0..9,A,B,C,D,E,F:
                     (0) Is 80% of the standard curve changer value.
                     (8) Is the same as the standard curve changer value.
                     (F) Is 120% of the standard curve changer value.
 
Each switch position is a 2.5% step in the curve changer value.
With a higher curve changer switch values the static advance will need to be advanced.
See the table below.
 
The unit is mounted using Velcro provided, The switches are waterproof and the unit should be operated with the cover on.
 
 

The switch closest to the cable marked R2 controls the Rear No2 cylinder.

The switch away from the cable market F1 controls the Front No1 cylinder.
 
 
Fig 1. Standard RS250 Curve Changer

This diagram shows both the ignition curves the power jet and power valve action with RPM.

The standard curve changer enables increased advance in the drive area and over rev retard.
 
 
 
Fig 2. 16 setting RS250 Curve Changer

This diagram shows the effects of the range of the 16 settings, allowing the user to fine tune the ignition map.
 
 
Installation Procedure

 
 
1. Advance the static timing
Initial Base setting
Set the curve changer unit to setting 8.
Advance the static plate by 8 degrees; this may require a slight widening of the slots.
 
ROTATE THE IGNITION ADJUSTER PLATE ANTI- CLOCKWISE  
 
Measure in rotation mm:
0.97mm per degree at the plate marked edge – 8 degrees is 7.7mm
( 0.73mm per degree at the pick-up surface - 8 degrees is 5.8mm )
 
Fine Adjustment
If the over-rev is brick walling (will not rev out at max RPM) but has strong acceleration
then turn the curve changer switch up one setting
 
If the over-rev is higher, but the acceleration not strong, then turn the curve changer switch down one setting
 
Specialist setting
To increase the curve changer effect (drive advance and over-rev) and retain the mid range,
the static plate needs to be advanced more and at the same time the curve changer setting increased
to return the timing to the correct level:
 
For 6 degrees = 5.8mm at ignition adjuster plate (at pick-up 4.4mm) = Setting 0
For 7 degrees = 6.8mm at ignition adjuster plate (at pick-up 5.1mm) = Setting 4
For 8 degrees = 7.7mm at ignition adjuster plate (at pick-up 5.8mm) = Setting 8
For 8.5 degrees 8.2mm at ignition adjuster plate (at pick-up 6.2mm) = Setting A
For 9 degrees = 8.7mm at ignition adjuster plate (at pick-up 6.6mm) = Setting F
 
 
2. Connect the curve Changer
 
Solder the Curve Changer wires onto these wires as follows:

Curve Changer Yellow     to     ‘White with Yellow stripe’

Curve Changer Blue        to     ‘White with Blue stripe’

Curve Changer Green     to     ‘green with Blue stripe’ (some models this is just green)

Curve Changer Green     to     ‘green with Blue stripe’ (some models this is just green)
 

It does not matter which green to which green/blue they are the same connection
Tape the joins with tape. Pull back the outer sleeving. Plug in the curve changer.
 
By using a tyraps, or the Velcro on the unit, the Curve Changer then can easily be fastened to the front of the frame,
for easy adjustment access.
 
 
3. Check
Remember to allow for carburetion changes, increase the main by 2 jet sizes to be safe.
Use of a detonation indicator or counter is recommended.
 
In Stock now
 
 
RS125 Honda : £245.00 + VAT
 
RS250 Honda / TZ250 Yamaha : £265.00 + VAT
 
 
You can now upgrade the original Curve Changers to the new 16-Setting Curve Changer
Upgrade RS125 : £130.00+VAT
Upgrade RS250 / TZ250 Yamaha : £160.00+VAT
(not supplied with the loom connector and existing original curve changer unit must be returned to us)
 
 
 

Exports of all parts supplied to outside EC Countries are exempt from UK VAT

Exports to EC Countries are exempt from VAT if a valid VAT registration number is supplied
 
 
CALL STEVE PATRICKSON
01274 583231  or  07738 626165
OR SEND YOUR E-MAIL TO
steve@sp125racing.com
 
 

Go To: 125 16 settings Ignition Curve Changer
 

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SP125 Limited Disclaimer
Honda, HRC and all other parts supplied by the SP125 Limited are not guaranteed when used in competition events.
As such, it is a condition of our making all parts available that it is solely the decision of each individual, rider, team member or team
whether they choose to use any part supplied and in doing so, absolve the manufacturer and SP125 Limited of any or all such claims,
including damage to equipment and/or injury to personnel irrespective of how caused.
All parts remain property of SP125 Limited until paid for in full.
All 'special order' parts, that are ordered specially under the instruction of the customer, are non returnable and non refundable.