sp125racing
Follow us at
  • sp125racing
  • Honda RS125
    • RS125 Genuine Honda HRC Parts
    • RS125 Engine Parts
    • VHM Piston Height Tool Guide
    • RS125 Chassis Parts
    • RS125 Honda Wheels Tyrewarmers Sprockets
    • RS125 Honda Crash Protectors
    • RS125 Honda Brembo Brakes
    • RS125 Honda Handlebars Levers & Footpegs
    • RS125 Honda Stands
    • RS125 Honda Quickshifters
    • Battle Shifter Fitting Instructions
    • RS125 Special Tools
    • RS125 Honda Fairings
    • RS125 Honda Seats
    • RS125 Honda Mudguards
    • HRC Datalogger & Detonation Counters
    • Detonation Detection System
    • Replacement for HRC Detonation Lead
    • RS125 16 Setting Ignition Curve Changer
    • RS125 Ignition Pulse Simulator
    • RS125 Throttle Position Sensor Checker
    • RS125 Gear Change Light
    • RS125 Powerjet Controller
    • RS125 Powervalve Controller Box
    • RS125 High Viz Temp Gauge
    • RS125 Ni-MH Battery Pack
    • RS125 Honda How To Order
  • HRC Setting Data & Maintenance Information
    • RS125R / RS250 Basic Concept of Power Jets
    • RS125 / RS250 Settings using Detonation Counters
    • RS125 / RS250 Settings according to seasonal conditions
    • RS125R / RS250R Functions of carburetor parts
    • RS250R Carburetor Settings
    • RS125R Parts Combination according to model years
    • RS250R Parts Combination according to model years
    • RS125R / RS250R Optimizing riding position
    • RS125R / RS250R Suspension Settings vol.1
    • RS250R Suspension Directionality
    • RS125R / RS250R Points of engine and frame assembly
    • RS125R / RS250R Notes on Engine Maintenance
    • RS125R / RS250R Notes on Frame Maintenance
    • RS125R / RS250R Conservation for engine power
    • RS125R / RS250R Running In / Warming Up / Position Adjustment
  • Honda RS250
    • RS250 Genuine Honda HRC Parts
    • RS250 Engine Parts
    • RS250 Chassis Parts
    • RS250 Handlebars, Levers & Footpegs
    • RS250 Brakes
    • RS250 Honda Stands
    • RS250 Honda Quickshifters
    • RS250 Bodywork
    • RS250 Bike Specification 2008
    • RS250 16 Setting Ignition Curve Changer
    • RS250 Ignition Pulse Simulator
    • RS250 Honda How To Order
  • Honda NSF250R
    • NSF250R Genuine Honda HRC Parts
    • NSF250R Engine Parts
    • NSF250R Honda Wheels Tyrewarmers Sprockets
    • NSF250R Honda Handlebars Levers & Footpegs
    • NSF250R Chassis Parts
    • NSF250R Honda Crash Protectors
    • NSF250R Honda Stands
    • NSF250R Honda Quickshifter
    • NSF250R Bodywork & Airbox Parts
    • NSF250R Honda How To Order
    • NSF250R High Viz Temp Gauge
  • Nova Gearbox - KTM Moto3
  • Terms and Conditions
  • Steve Patrickson Profile
  • Race Team Archives
    • 2023 sp125racing Team
    • 2022 sp125racing Team
    • 2021 sp125racing Team
    • 2020 sp125racing Team
    • 2019 sp125racing Team
    • 2018 sp125racing Team
    • 2017 sp125racing Team
    • 2016 sp125racing Team
    • 2015 sp125racing Team
    • 2014 sp125racing Team
    • 2013 sp125racing Team
    • 2012 sp125racing Team
    • 2011 sp125racing Team
    • 2010 sp125racing Team
    • 2009 sp125racing Team
    • 2008 sp125racing Team
    • 2007 sp125racing Team
    • 2006 sp125racing Team
    • 2005 sp125racing Team
    • 2004 sp125racing Team
    • 2003 sp125racing Team
    • 2002 sp125racing Team
    • Tom Carne Profile
    • Jordan Weaving Profile
    • Rob Guiver Profile
    • Brad Ray Profile
    • Chrissy Rouse Profile
    • Matt Davies Profile
    • Ben Barrett Profile
    • Matthew Hoyle Profile
    • Lee Costello Profile
    • Nicole McAleer Profile
    • Connor Behan Profile
    • Luke Hinton Profile
    • Jordan Malton Profile
    • Dan Moreton Profile
    • Michael Smith Profile
    • Luke Jones Profile
    • Jamie Ashby Profile
    • Mark Clayton Profile
    • Joel Marklund Profile
    • Elliot Lodge Profile
    • Elliot Lodge 2018 Profile
    • Elliot Lodge 2019 Profile
    • Harvey Claridge 2018 Profile
    • Harvey Claridge 2019 Profile
    • Franco Bourne 2019 Profile
    • Calum Beach 2019 Profile
    • Jeremy Knight 2019 Profile
    • Cameron Horsman 2019 Profile
  • Contact
  • 2022 Race Dates
  • 2023 Race Dates

HRC Setting Data & Maintenance Information

RS125R / RS250 Basic Concept of Power Jets


Please  'Refresh' this page every time you visit.         If it is slow to reload, you know then that this page has been updated since your last visit.

Picture
Picture
Picture
See Figure 1 below, which depicts the output characteristics associated with the full throttle engine operation The graph contains the range B at around the peak power, the range A before the peak power, and the range C for over-revving ranges, each of which requires the proper fuel flow rate. Settings using Main jet only, however, provides richer mixtures to the ranges A and C if they meet the fuel flow rate requirements for the range B.
Picture
In Figure 2, the gently sloping, linear graph represents fuel flow rate. From Figure 1 showing the power curve gives a mountain-shaped graph, we can understand that a single Main jet does not provide ideal fuel mixtures for all of the A, B, and C. The power jet can make the flow rate closer to the ideal, mountain-shaped graph.
Picture
The year 1999 and earlier RS125R has carburetor settings which give fuel mixtures suited for the peak power, using relatively small Pwj#40s to avoid detonation.
The year 2000 and later model has the same carburetor specifications as the RS250R, so the same settings as the RS250R can be applied to the model. Accordingly, the use of larger #48 power jets give more torque. However, since the RS125R is different from the RS250R in engine capacity, the presence of RC valves, and service speed range, it has settings intended for the RS125R. 

 •Changes in carburetors (1998 - 2000 models)
                                '98•'99                2000
 MJH, Body               ø3.5                   ø3.7
 FLOAT LEVEL         8.5mm               8.0mm

•Engine characteristics with power jet carburetors (2000 year model and later)
 
1)Excellent over revving characteristics

2)Increased torque at speeds (10000 and over rpm) associated with rising
3)Easy throttle opening
4)High cornering performance resulting from smooth, linear revving up
5)Proper engine braking performance 


Actual setting 
The fundamental setting should be that the speed range preceding the peak power has torqueful output while the high-speed range has excellent over revving characteristics.
The standard settings at the time of leaving the factory contain power jets (Pwj) of #40. So, the Pwj should be changed to #48 after running in, making sure the standard settings.
Jet needle/Main jet settings (for snapping after warming up) according to circuit run weather conditions.



Basically, R1268/34-4clip or R1269/34-4clip will be used for Jet needle. Snapping will be used to make sure response for final determination.


Select Main jet which can provide at least 13000 rpm or more at each gear

Jets should be so selected that engine feeling does not significantly change when the power jets become ineffective. For instance, settings for the main region seems defective if the engine feeling drastically seems lighter or heavier when power jets become ineffective. It is recommended that shift ups be made at around 13200 rpm and smooth and higher engine speed be aggressively used to keep engine speeds high after shift ups for higher, increased acceleration. 



More practical specifications 
Various optional parts are provided to make more practical the RS125R fitted with power jet carburetors.

MJH (main jet holder)
    •Optional 3.9 diameter against standard 3.7 diameter
     Switch to this 3.9 diameter MJH will give you more smooth, powerful performance immediately after opening the throttle. 

     The MJH, however, should be returned to the 3.7 if hunting occurs. Hunting, even if you tolerate, will degrade your riding.
     (In comparison with 1998 and 1999 year models, the 2000 year model will give you less hunting and hesitation, so you can use aggressively 3.9 MJH.)

•Optional Jet needle parts have a 33-needle against the standard a 34-needle.Their use depends upon weather conditions or course layouts (rich by 0.5 step for the same step number)  



Pwj#48 settings for 1998 and 1999 models 
Even the 1998 and 1999 models can be modified to have the same Pwj#48 settings as the year 2000 specifications. At the time of the modifications, changes of the oil level to 8.0mm will provide the same power feeling at high-speed ranges as the year 2000 model.

In addition, changes of MJH to 3.5 to 3.7 to 3.9 diameter will give more torque in the lower and middle speed ranges. Hunting or rich feeling, however, will tend to occur more frequently.

To solve rich feeling while keeping the torque feeling, Jet needle step numbers will be slightly reduced, leading to less rich feeling, improved responses over the entire speed range with easier riding ensured. The MJH and Jet needle should be well balanced. Seeking torque feeling only will result in hunting or rich feeling problems causing degraded riding and time. 

Settings should be selected which meet your ways of riding (opening the throttle).
For settings for the years 1998 and 1999 models, either conventional Pwj#40 settings or the year 2000 model settings should be selected according to riders' choice.

  Changes in oil levels in carburetors will be accompanied by major setting changes. If you feel a problem in setting, it is recommended to return to the standard settings. 
Picture
As shown in the figure, degraded power (torque) feeling has been recovered by lowering secondary compression. In addition to modifications to ignition timing at around maximum output engine speeds, aggressive introduction of the new carburetor power jets at speeds higher than the maximum output speeds has resulted in increased output and recovery of a drop in output power following the peak power. For this, the engine service range moves upwards as compared with the 1998 year model, which is a feature of the power jet carburetor specifications.
Picture
Engine characteristics with power jet carburetors 
1)Excellent over revving characteristics
2)Significantly increased torque at speeds (10000 and over rpm) associated with rising
3)Easy throttle opening
4)High cornering performance resulting from smooth, linear revving up
5)Proper engine braking performance
Actual setting 
The fundamental settings should be that low and middle speed ranges have more torque with linear output characteristics, allowing easy throttle opening. 
The higher speed range should have excellent over-revving characteristics. 
The standard settings at the time of leaving the factory have power jets of #40. 

So, the power jets should be changed to #48 after running in, making sure the standard settings.

Jet needle/Main jet settings (for snapping after warming up) according to circuit run weather conditions.

Basically, R1268/34-4clip or R1269/34-4clip will be used for Jet needle. Snapping will be used to make sure response for final determination.

Select Main jet, which can provide at least 13000 rpm or more at each gear
Jets should be so selected that engine feeling does not significantly change when the power jets become ineffective. For instance, settings for the main region seems defective if the engine feeling drastically seems lighter or heavier when power jets become ineffective. It is recommended that shift ups be made at around 13500 rpm and smooth and higher engine speed be aggressively used to keep engine speeds high after shift ups for higher, increased acceleration.

  Basically, changes to Main jet and Needle jet only should give the nearly best settings throughout the year. However, since engine service speed range moves slightly higher than before, changes should be made to final and transmission gears to ensure speeds during rising at the corners.
More practical specifications 
Various optional parts are provided to make more practical the RS250R fitted with power jet carburetors.
 

 MJH (main jet holder)
Optional 3.9 diameter available against standard 3.7 diameter
Switch to this 3.9 diameter MJH will give you more smooth, powerful performance immediately after opening the throttle. The MJH, however, should be returned to the 3.7 if hunting occurs. Hunting, even if you tolerate, will degrade your riding.  



Optional Jet needle parts have a 33-needle against the standard a 34-needle. Their use depends upon weather conditions or course layouts (rich by 0.5 step for the same step number)  


Changes to Pwj cut.
12500 rpm and 12250 rpm are available against the standard 12750 rpm.
Earlier cut speeds will ensure high-end revving properties, but care should be taken to avoid detonation.
Key to power jet carburetor setting
<Notes on settings> 

1)Settings should be so made as to ensure torqueful low and middle speeds with smooth high-end revving, instead of seeking a punch over the power band. At this time, power jet specifications should not be set by feeling, but should be made by checking the course for vehicle speeds (for instance, actual vehicle speeds can be determined by checking gears and engine speeds when passing an object on the straight lane). Since power jet specifications give torqueful engine characteristics which urge you to use higher engine speed beyond the peak rpm, you may feel slower in vehicle speed. Do not depend upon your feeling only when judging vehicle speeds.


2)Easiness to open the throttle is important. Significant changes in characteristics, such as changes to secondary compression, will degrade the overall balance, eliminating the positive aspects of power jet carburetors. If you have a problem in changing specifications or parts, standard settings should be restored.3)Ensure Carburetor box sealing and making full use of ram pressure.
Setting of power jet cut off point 
RS250
 mode          colour code        Pwj cut off point(rpm)            remark

    1               -                      12750                                 Standard
    2             blue                   12500                                 Included parts 
    3             yellow                12250                                 Optional parts

Settings of power jet cut off point depend upon the use of gears according to course layout. More specifically, the standard mode 1 should be used for the high-speed circuit where 5th or 6th gear are frequently used, the mode 2 for middle-speed circuit, such as Sugo, and the mode 3 for the low-speed circuit where 5th or 6th gears are seldom used (see Figure below for recommended modes). If the mode 3, where power jets become ineffective in early stages, is used at high-speed course, ineffective power jets will cause significant lean fuel mixture during acceleration in the 5th or 6th gears, resulting in frequent occurrence of detonation.
When power jet cut modes are to be changed, course layout, detonation counters or piston burning should be taken into account.



return to hrc setting information

return to honda rs125
home
SP125 Limited
22 Walker Wood,  Baildon,  Shipley,  West Yorkshire,  BD17 5BE,  England
Telephone 01274 583231      steve@sp125racing.com      Mobile 07738 626165
Picture
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.
Powered by Create your own unique website with customizable templates.