Derestricting the yamaha dt125 r

1. Scrimsmustangs Classic Yamaha Restorations
3DB1 THROUGH TILL 3RN9 , 88 UNTIL 96 MODEL YEARS !
FIRST REMOVE THE EXHAUST SYSTEM AS FOLLOWS , FIRST REMOVE THE RIGHT HAND SIDE SIDEPANEL AND
REMOVE THE EXHAUST SECUERING BOLT JUST TO THE LEFT OF THE BOTTOM REAR CORNER OF THE FUEL TANK
WITH A 10MM SOCKET OR RING SPANNER. THEN YOU WILL FIND ANOTHER EXHAUST MOUNTING BRACKET ON
THE LARGEST PART OF THE EXHAUST, REMOVE THE BOLT SECUERING IT TO THE FRAME ,NOT VIA THE BOLT ON
THE EXHAUST ITS SELF REMOVE THIS THE SAME WAY. AFTER YOU HAVE DONE THIS REMOVE THE 2 NUTS
SECUERING THE EXHAUST TO THE CYLINDER BARREL MANIFOLD WITH A 12MM SOCKET, THEY MAY BE SEIZED A
COULD POSSIBLY TAKE OUT THE ENTIRE STUD, DON’T WORRY IF THEY DO AS THEY WILL SCREW BACK IN NO
PROBLEM. THE EXHAUST IS NOW READY DO BE REMOVED, JUST GIVE IT A WIGGLE AND FIRM PULL AND IT WILL
COME OFF FAIRLY EASILY. CHECK THE GASKET IS STILL IN THE MANIFOLD OR STILL CONNECTED TO THE
EXHAUST ITS SELF AS IT NEEDS TO BE REFITTED WITH THE EXHAUST.
NOW LOOK INSIDE THE EXHAUST WERE IT MEETS THE MANIFOLD YOU WILL SEE AN INSERT “SMALL TUBE”
SECURED BY 3 SMALL SPOT WELDS, REMOVE THE WELDS WITH A DREMMEL OR DRILL OR ANYTHING YOU HAVE
IN YOUR TOOLS TO DO THE JOB, AND THEN REMOVE IT.THAT’S THE EXHAUST DERESTRICTED, REFIT IS THE
REVERSE OF REMOVAL !
WITH THE EXHAUST REMOVED YOU WILL NOW BE ABLE TO INSERT YOUR FINGER INTO THE EXHAUST MANIFOLD
OF THE ENGINE, DON’T WORRY THERE IS NOTHING SHARP IN THERE TO WORRY ABOUT !
“WARNING” ONLY WHEN THE ENGINE IS COLD AND DO NOT TURN THE ENGINE OVER WHEN CARRYING OUT THIS
NEXT PROCEDURE !
DON’T WORRY YOU DON’T NEED TO PLACE YOUR FINGER IN THE MANIFOLD YET, ON THE LEFT SIDE OF THE
CYLINDER BARREL YOU WILL SEE A ROUND COVER WITH A 10MM BOLT IN THE CENTRE AND 2 SMALL ALLEN
SCREWS EITHER SIDE OFF IT, REMOVE IT , 10MM BOLT FIRST THEN THE 2 SMALL ALLEN SCREWS.
UNDERNEATH THE COVER YOU WILL FIND A SLEAVE WITH A SMALL PEG IN IT THAT SECURES IT TO THE CAP YOU
HAVE JUST REMOVED. REMOVE THE SLEAVE AND YOU WILL HAVE ACCESS TO THE “YPVS DIAMOND” WITH A
THREADED HOLE IN THE CENTRE WERE THE 10MM BOLT YOU REMOVED SCREWS INTO AND A DOT STAMPED
INTO IT !
NOW YOU NEED TO INSERT YOUR FINGER INTO THE MANIFOLD”TO THE TOP”, AT THE SAME TIME SLOWLY ROTATE
THE YPVS DIAMOND, YOU MAY NEED PLIERS TO DO THIS ,AS YOU DO THIS YOU WILL BE ABLE TO FEEL THE YPVS
ROTATING INSIDE THE EXHAUST PORT, WHEN YOU FEEL IT FLUSH WITH THE TOP OF THE PORT THAT’S IT.
REFIT IS THE REVERSE OF THE REMOVAL. CLEAN THE MATING SURFACES OF THE COVER AND THE CYLINDER
BARREL AND REASSEMBLE WITH A LITTLE INSTANT GASKET SEALER. YOUR BIKE IS NOW DERESTRICTED AND
READY TO RUN !
3RM9 THROUGH TILL 3RME , 97 TILL MID 99 MODELS !
Home 1980 Yamaha DT175MX DT175 4J4 1981 Yamaha DT125MX DT125 4J3 1983 Yamaha IT490 IT490K 26A more...

2. THE PROCEDURE FOR THE EXHAUST IS IDENTICAL TO THE MODELS PREVIOUSLY COVERED, HOWEVER THE
MODELS COVERED IN THIS SECTION HAVE THE SERVO FITTED AS STANDARD TO ELECTRONICLY OPERATE THE
YPVS SYSTEM.
TO CHECK THE CORRECT OPERATION AND SETTING OF THE YPVS SYSTEM ON THESE MODELS. WHEN THE
EXHAUST IS OFF FOR DERESTRICTION IT ALLOWS VERY ACCURATE CHECKING OF THE YPVS WITH THE EXHAUST
REMOVED.
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WITH THE EXHAUST REMOVE PLACE YOUR FINGER GENTLY INSIDE OF THE EXHAUST PORT TO THE TOP OF THE
PORT AND TURN THE IGNITION TO THE ON POSITION SO YOU CAN HEAR THE YPVS MAKE ITS CHECK/CLEANING
CYCLE, YOU WILL FEEL THE YPVS MOVE THROUGH ITS CYCLE. WHEN IT FINISHES YOU SHOULD FEEL THE YPVS
FLUSH WITH THE TOP OF THE PORT WITH NO OBSTRUCTIONS TO THE TOUCH. IF YOU CAN ITS SET CORRECTLY.
“NEVER TURN THE ENGINE OVER WHEN CARRYING OUT THIS PROCEDURE”
»IF YOU CANT YOU NEED TO AJUST THE YPVS VIA ITS CABLES, THERE LOCATED ON THE LEFT SIDE OF THE
CYLINDER BARREL AND SECURED IN THERE POSITION WITH A 9MM LOCK NUT ON BOTH CABLES.
THE WAY TO DO THIS IS TO REMOVE THE COVER SECURED WITH THE 2 SMALL ALLEN SCREWS, WHEN THIS IS
REMOVED YOU WILL BE ABLE TO SEE THE YPVS CABLE PULLY WHEEL. IN BETWEEN THE CABLES ON THE PULLY
WHEEL YOU WILL SEE A GROOVE ,WHEN THIS GROOVE IS LINED UP WITH THE DOT THAT IS STAMPED INTO THE
CYLINDER BARREL BEHIND THE PULLY WHEEL. WHEN YOU TURN THE IGNITION SWITCH TO THE ON POSITION
,AFTER THE YPVS CYCLE FINISHES, IF THE GROOVE IS ALIGNED WITH THE DOT THE YPVS IS CORRECTLY SET FOR
FULL POWER OPERATION. IF NOT ADJUST AS REQUIRED.
PLEASE NOTE THAT SOME BIKES MAY NEED THE YPVS DIAMOND ROTATING 180 DEGREES,IF THE DOT STAMPED
ON THE DIAMOND IS AT THE BOTTOM ROTATE THE DIAMOND 180 DEGREES !
ONCE CORRECT AJUSTMENT IS GAINED REFIT THE EXHAUST, REVERSE OF REMOVAL, LOCK THE YPVS CABLES
INTO POSITION, REFIT THE PULLY WHEEL COVER WITH A LITTLE STANT GASKET SEALER.
NOW FOR THE DIFFICULT PART ON THESE MODELS !
AT THE FRONT OF THE 2 STROKE OIL TANK ON SOME OF THESE BIKES YOU MAY FIND A SMALL SILVER/GRAY BOX
WITH A FEW WIRES COMING FROM IT, IF YOU DON’T IT’S A BIT LESS WORK FOR YOU. IF YOU DO READ ON. THESE
ARE THE WIRES SWITCHING THE CDI UNIT. THERE SHOULD BE A RED, YELLOW, BLUE AND A GREEN.
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THE RED GOES TO A BROWN AT THE REGULATOR
THE YELLOW GOES TO A RED/WHITE STRIPPED ON THE PULSE COIL BEHIND THE L/H ENGINE CASE.
THE GREEN GOES TO THE RED/WHITE AT THE CDI.
THE BLUE GOES INTO A PLUG FROM WERE THE YELLOW IS COMING FROM.
NOW FOR THE CHANGES, DISCONNECT THE RED AND THE BLUE AND ISOLATE THEM. YELLOW AND GREEN WILL
REMAIN, JOIN THEM TOGETHER, THEN JOIN THE REMAINING RED/WHITE WIRE TO EACH OTHER. MAKE SURE
EVERYTHING IS PROPERLY INSULATED WITH DECENT ELECTRITIANS TAPE. IF ITS NOT SINKING IN JUST READ IT A
FEW TIMES.
THE BIKE IS NOW DERESTRICTED AND READY TO RUN !»
IF NO SILVER BOX IS FITTED AND THIS MOD CANNOT BE CARRIED OUT SWAP TO A PRE 96 CDI UNIT , HOWEVER
YOU WILL STILL SEE A MARKED IMPROVEMENT IN PERFORMANCE BUT PRE 96 CDI UNITS HAVE A HIGHER RPM
REV LIMITER.
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3RME THROUGH TILL 3RMM MODELS , MID 99 TILL 03 MODELS.
“NO STEERING LOCK BUILT INTO THE IGNITION SWITCH”
THESE MODELS WERE MADE REALLY DIFFICULT TO DERESTRICT BY YAMAHA DUE TO EUROPEAN POWER TO

3. WEIGHT RATIOS AND EMISSIONS LAWS IN EUROPE.
THE ONLY GOOD THING IS THE YPVS NEEDS NO AJUSTMENT “ON 99% OF THEM ANYWAY” BUT CHECK ANYWAY
WITH THE METHOD DESCRIBED IN THE EARLYER MODEL SECTION.
REMOVE THE EXHAUST AS DESCRIBED IN THE EARLYER SECTION, THE RESTRICTION IS NOW MORE DIFFICULT TO
REMOVE !!! IT IS TO SEMI CIRCULAR PLATES AND A LOT OF WIRE MESH LOCATED IN THE LARGEST PART OF THE
EXHAUST. TO REMOVE THEM THE EXHAUST NEEDS CUTTING OPEN WITH A GRINDER OR HACKSAW AND RE
WELDING .
I HAVE KNOWN ONE OF THE SEMI CIRCULAR PLATES TO WORK LOOSE BEFORE BY THEMSEVES , SO IF YOU HAVE
A RATTLE IN YOUR EXHAUST ITS PROBABLY CAUSED BY THIS.
NEXT REMOVE THE CARB, FIRST REMOVE THE FUEL PIPE, REMEMBER TO TURN THE FUEL TAP TO THE OFF
POSITION. LOOSEN THE 2 JUBILEE FASTNERS THAT SECURE THE CARB TO THE INLET MANIFOLD AND AIRBOX
RUBBER.
THEN REMOVE THE BLACK PLASTIC BOTTLE THAT IS SECURED TO THE FRAME THAT PUSHES INTO THE AIRBOX
RUBBER IN BETWEEN THE CARB AND AIRBOX.
WHEN YOU HAVE REMOVED THE BOTTLE FIRMLEY BUT GENTLEY PULL THE CARB FROM THE RUBBERS FROM
THE LEFT SIDE OF THE BIKE. WHEN YOU HAVE THE CARB FREE REMOVE THE 2 CROSSHEAD SCREWS FROM THE
TOP AND PULL THE TOP FREE FROM THE CARB AND REMOVE THE SLIDE. THEN PUT THE CARB TO ONE SIDE.
“THIS PART IS IMPORTANT “
NOW REMOVE THE INLET MANIFOLD RUBBER FROM THE CRANKCASES, BY REMOVING THE 4, 10MM BOLTS
,REMOVE THE SMALL BLACK RUBBER 2 STROKE OIL FEED PIPE FROM THE RIGHT HAND SIDE OF THE MANIFOLD
AND BLACK IT WITH A MATCH STICK OR SMALL SCREW. THEN CAREFULLY PRISE IT FROM THE CRANKCASES.
WHEN YOU HAVE THE MANIFOLD FREE YOU WILL SEE A SQUARE RUBBER NOSE PROTRUDING FROM THE
BOTTOM OF IT. THIS NEEDS REMOVING , CUT IT OFF WITH A STANLEY KNIFE OR SIMILAR “BE CAREFULL AND
WATCH YOUR FINGERS” ONCE THE NOSE IS REMOVED THE HOLE NEEDS CHAMPFERING OUT FROM THE CENTRE
OF THE HOLE TO THE EDGE OF THE MANIFOLD TO CREATE A SMOOTH FREE FLOWING FUEL FLOW. IF YOU DON’T
FEEL LIKE TACKELING THIS SEND IT TO ME WITH £6 AND I WILL REPLACE YOUR ORIGINAL WITH A MODIFIED ONE.
REFIT IS THE REVERSE OF REMOVAL, USE A LITTLE INSTANT GASKET SEALER . WHEN REFITTING THE BLACK
BOTTLE TO THE AIRBOX RUBBER, COVER THE HOLE IN THE BOTTLE WITH INSULATION TAPE BEFORE REFITTING
IT. OR ALTERNATIVELY FIT THE RUBBER FROM A PRE 99 MODEL THAT DOES NOT HAVE THE BOTTLE FITTED.
ALSO REMOVE THE RUBBER AIRBOX NOSSLE FITTED TO THE TOP OF THE AIRBOX UNDER THE SEAT TO LET THE
BIKE BREATH A LITTLE BIT BETTER. DON’T DRILL HOLES IN THE SIDE OF THE AIRBOX.
NEXT REMOVE THE HEADLAMP SHROUD BY REMOVING THE 2 SCREWS/BOLTS ,ONE ON EITHER SIDE OF THE
SHROUD. THEN REMOVE THE HEADLIGHT BY REMOVING THE 10MM BOLTS SECUERING IT TO THE BRACKET,
UNPLUG THE WIRING CONNECTIONS FROM THE BULBS AND PLACE THE HEADLIGHT TO ONE SIDE. YOU SHOULD
NOW BE ABLE TO GAIN ACCESS TO THE BOTTOM OF THE SPEEDO, UNSCREW THE SPEEDO CABLE WITH PLYERS,
DISCONNECT THE WHITE PLASTIC WIRING CONNECTOR BLOCK THEN REMOVE THE 2 SPLITPINS SECUERING THE
SPEEDO TO THE BRACKET IT SITS ON ”THERE SMALL AND FIDDLY SO TAKE YOUR TIME” WHEN YOU HAVE DONE
THIS PULL THE SPEEDO UP FROM THE BRACKET. FITTED IN THE BOTTOM OF THE SPEEDO IS THE BACK LIGHT
THAT LIGHTS UP THE SPEEDO IN THE DARK WHEN YOUR LIGHTS ARE SWITCHED ON, AND THERE IS A WHITE
PLASTIC INSERT PUSHED INTO THE BOTTOM ALSO, PRISE THIS OUT AND YOU WILL SEE WHAT LOOKS LIKE A
SMALL GLASS FUSE. THIS IS THE REED SWITCH. WHEN THIS IS REMOVED YOU WILL NEED TO SLICE THE BLACK
PLASTIC SURROUNDING THE WIRES SO YOU CAN FURTHER SEPARATE THE REED SWITCH FROM THE
BACKLIGHT. PUSH THE REEDSWITCH THROUGH THE SPEEDOS BRACKET SO ITS FREE. DON’T CUT IT OFF JUST
LEAVE IT FREE UNDERNEATH THE CLOCKS. THEN REFIT THE SPEEDO THEN THE HEADLIGHT AND SHROUD ,THE
REVERSE OF THE REMOVAL.
THE BIKE IS NOW DERESTRICTED AS MUCH AS THE CDI AND CARB FITTED WILL ALLOW HOWEVER YOU SHOULD
NOTICE A MARKED INCREASE IN PERFORMANCE, THE CDI HAS A LOWER REVLIMITER AND THE CARB IS
DESIGNED FOR BETTER EMISIONS RATHER THAN POWER. HOWEVER I CAN AD THAT SOME LATE 52 REG AND 03
REG 3RMM MODELS SEEM TO HAVE THE UNRESTRICTED REVLIMITER CDI THESE ARE MARKED 3RM­20 AND
RESPOND REALLY WELL TO THESE MODS.EVEN SO AS I HAVE SAID YOU WILL NOTICE A BIG IMPROVEMENT
REGARDLESS OF THE CDI THAT IT FITTED TO THE BIKE BUT IF YOU HAVE THE 3RM­20 CDI ALL WELL AND GOOD.
IF ITS STILL NOT ENOUGH THERE IS ONLY ONE WAY TO FULLY DERESTRICT THESE MODELS, AND THAT IS TO
RETRO FIT PARTS FROM THE 89 TILL 96 MODELS IF THE POWER IS STILL NOT ENOUGH. 89 3RN1 CDI ARE THE BEST

4. THEY ARE THE MOST POWERFULL EVER PRODUCED WHEN DERESTRICTED.
PARTS THAT WILL NEED TO BE SWAPPED ARE AS FOLLOWS !
COMPLETE WIRING LOOM
CDI UNIT, EARLYER THE BETTER !!!
REGULATOR/RECTIFIER.
IGNITION SWITCH
LIGHT SWITCHES
STATORPLATE
FLYWHEEL “ ITS WEIGHTED ON 3RME 3RMJ AND 3RMM MODELS”
CARB
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3 WIRE YPVS SERVO MOTOR “AS THE 5 WIRE FITTED AS STANDARD IS NOT COMPATIBLE WITH THE EARLY TYPE
CDI UNITS“. EARLY 97 98 DT125R TYPE OR ANY TDR 125 TZR 125.
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FITTING OF THESE IS THE ONLY WAY TO GUARENTEE FULL POWER DERESTRICTION ON 99% OF THESE MODELS
AS THE EARLY TYPE UNDER FUEL TANK CDI UNIT IS NOT COMPATABLE WITH THE LATER MODEL WIRING LOOM..
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IF IN DOUBT JUST ASK !
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ON 3RME ONWARD BIKES , BUYING A CDI FROM GERMANY ETC ON EBAY WILL NOT SOLVE THE PROBLEM AS ALL
OF THE EU USE THE SAME RESTRICTED CDI UNIT. THERE IS NO FULL POWER CDI,S FOR THESE BIKES , ITS AN
INTERNET FORUM MYTH. EXCEPT FOR THE ONE OR TWO 3RMM BIKES THAT I HAVE CAME ACROSS THAT DON’T
SEEM TO BE AS BAD, I HAVE YET TO BE ABLE TO MAKE OUT THE PART NUMBER ON ONE OF THESE THOUGH.
PEOPLE SELLING THESE OPEN CDI UNITS ON EBAY MAY BE SELLING A FULL POWER 3RMM UNIT BUT I WOULD
NOT TAKE A CHANCE ON IT AS THERE MORE THAN LIGHTLY JUST SELLING THE RESTRICTED UNIT AFTER A FULL
POWER RETRO FIT CONVERSION.
IF YOU CAN GET A PART NUMBER IF YOUR CONSIDER BUYING AN OPEN CDI FROM EUROPE GET THE PART
NUMBER IF POSSIBLE AND CHECK IT WITH THE PART NUMBER ON YOURS IF YOU CAN MAKE IT OUT. OR WITH
YOUR LOCAL YAMAHA DEALER AND YOU WILL NO DOUBT FIND ITS IDENTICAL TO THE TYPE YOU ALREADY HAVE.
PRE 3RME BIKE USE A DIFFERENT WIRING LOOM AND THE EARLY TYPE FULL POWER CDI UNITS ARE JUST NOT
COMPATIBLE WITH THE LOOM AND YPVS SERVO. SO THE RETRO FIT IS THE ONLY WAY TO GET AROUND IT.
I HOPE THIS HELPS, IF YOU HAVE ANY QUESTIONS JUST ASK, DON’T WORRY JUST TAKE YOUR TIME AND YOU
SHOULD HAVE NO PROBLEMS JUST MORE GO !!!
YOU CAN ALSO FIT A SET OF RACING REEDS , BOYESEN OR HY TEC ETC AND A PERFORMANCE EXHAUST SUCH
AS A DEP , FRESCO BIGONE OR ARROW ETC AFTER YOUR BIKE IS DERESTRICTED. THESE WILL GIVE MORE
TORQUE AND A SNAPPIER THROTTLE RESPONSE.
PERSONALY I WOULD CARRY OUT THE RETRO FIT FIRST ON THE LATER BIKES. THE PERFORMANCE EXHAUSTS
ETC WILL NOT MAKE THAT MUCH OF A DIFFERENCE ANYWAY WITH A RESTRICTED ELECTRICAL SYSTEM.

5. IF YOU WOULD LIKE THE SAME POWER DELIVERY AS THE EARLY BIKE YOU CAN PEG THE YPVS IN THE FULLY
OPEN POSITION SO YOU GET THE POWER KICK AT AROUND 6500 RPM. I LIKE THE POWER DELIVERY LIKE THIS
MYSELF.
THAT’S ABOUT IT , THANKS AND HAVE FUN.
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REMEMBER A SERVICE IS ALWAYS A GOOD WAY TO KEEP YOUR BIKE RUNNING WELL AND THIS IS A GOOD TIME
TO CARRY IT OUT, FRESH OIL A NEW PLUG AND A CLEAN AIRFILTER AND AIRFILTER BOX. YOU WILL BE
SURPRISED HOW MUCH A DIRTY CLOGGED AIRFILTER WILL AFFECT THE PERFORMANCE OF YOUR BIKE.
DT125RE AND DT125X 2004 ONWARD !
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THE NEW MODEL BIKES ARE REALLY STILL MORE OR LESS THE SAME AS THE OLD BIKE EXEPT FOR THE NEW
STYE BODYWORK AND THE FITMENT OF THE ELECTRIC START AS OPPOSED TO THE KICKSTART. ITS IDENTICAL
TO THE DT230 LANZA THAT’S BEEN AROUND SINCE 96 ALTHOUGH NOT OFFICIALY IMPORTED INTO THE UK BY
YAMAHA.
THERE VERY EASY TO DERESTRICT COMPARED TO THE OLDER VERSION.
THERE IS NO REEDSWITCH FITTED ON THESE BIKES , THE EXHAUST HAS NO RESTRICTION AS SUCH FITTED,
HOWEVER IT IS FITTED WITH A HOTCAT CATALYTIC CONVERTER THAT IS WORSE THAN THE OLD RESTRICTIONS.
IT IS REMOVABLE WITH DIFFICULTY , THE EXHAUST NEEDS CUTTING OPEN AT THE LARGEST PART OF THE
EXPANSION CHAMBER TO GET AT IT.
NO DOUBT THAT WHEN THE BIKE NEEDS ITS FIRST MOT TEST IT WILL NEED THE CAT, SO I WOULD JUST FIT A DEP
SYSTEM ETC. OR A DERESTRICTED EARLY MODEL EXHAUST , THERE SLIGHTLY DIFFERENT BUT FIT WITH VERY
MINOR MODS. ONE BRACKET NEEDS MOVING AND THE TAILPIPE NEEDS SLEAVING AS THEY ARE SLIGHTLY
DIFFERENT DIAMETERS WERE THEY JOIN THE MEET.
ALSO THE INLET MANIFOLD IS RESTRICTED IN THE SAME WAY AS THE 99 TILL 03 MODELS , JUST FOLLOW THE
SAME PROCEDURE FOR THIS. SEE THE PREVIOUS SECTION FOR DETAILS.
ALSO FOLLOW THE EARLIER PROCEDURE WITH THE BLACK PLASTIC BOTTLE FITTED TO THE AIRBOX TO CARB
RUBBER.
THE MAIN RESTRICTION ON THESE BIKES IS A REV LIMITER BUILT INTO THE CDI UNIT, BUT FORTUNATELY ITS
EASILY REMOVED ON THESE MODELS. GOING INTO THE SPEEDO IS A 4 WIRE CONNECTING BLOCK, THERE ARE
ONLY 3 WIRES ON THE SPEEDO SIDE OF THE CONNECTOR AND 4 WIRES ON THE LOOM SIDE. FIND THE
GREEN/BLACK WIRE ON THE LOOM SIDE OF THE CONNECTOR, SNIP IT FROM THE BLOCK, EXTEND IT AND CRIMP
AN EYLET ONTO IT AND EARTH IT TO THE FRAME VIA THE TOP RADIATOR MOUNT BOLT. THAT WILL REMOVE THE
REVLIMITER FROM THE CDI UNIT.
CHECK THE YPVS SYSTEM FOR CORRECT AJUSTMENT THE SAME WAY AS DESCRIBED AS FOR PREVIOUS
MODELS.
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28 TO 33 BHP FOR ALL MODELS !
THERE IS A WAY TO GAIN EVEN MORE POWER FOR THESE BIKES WITH SOME SIMPLE BOLT ON MODS.
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THERE ARE COUPLE OF ITALIAN BUILT YAMAHA 125,S THAT USE VIRTUALY THE SAME ENGINE AS THE DT125R.
THE TDR125 AND TDR125R BELGARDA, THE TZR125R AND TZR125R BELGARDA THAT WILL DONATE THE PARTS
SECOND HAND AND PRETTY CHEAP VIA EBAY ETC.
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THEY RUN A CHROME CYLINDER SLEAVE WITH BETTER PORTS AND A BETTER COMPRESION RATIO AND A BIG
DELORTO CARB.
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6. IF YOU CAN GET THE FOLLOWING FROM ONE OF THESE BIKE YOU WILL MAKE BIG POWER FOR A DT125R.
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CDI
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CYLINDER HEAD
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CYLINDER BARREL
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DELORTO CARB WITH INLET MANIFOLD AND CARB TO AIRBOX RUBBER “INLET AND AIRBOX RUBBERS MUST
COME FROM THE TDR,S AS THE AIRBOX IS DIFFERENT ON THE TZR MODELS..
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THE CARBS ARE USUALY CALLED “VERGASSERS” IN GERMANY , THAT’S WERE YOUR MOST LIKELY TO FIND
THESE BREAKING FOR SPARES ON EBAY ETC.
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YOU WONT GET AS MUCH POWER WITHOUT A CDI CONVERSION ON THE MID 99 TILL 03 DT. HOWEVER THE TDR
AND TZR CDI,S ARE A STRAIGHT SWAP ON ALL DT,S FROM 89 TILL 99 .
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2004 ON DT125RE AND DT125X !
THE NEW MODEL BIKES ARE REALLY STILL MORE OR LESS THE SAME AS THE OLD BIKE EXEPT FOR THE NEW
STYE BODYWORK AND THE FITMENT OF THE ELECTRIC START AS OPPOSED TO THE KICKSTART. ITS IDENTICAL
TO THE DT230 LANZA THAT’S BEEN AROUND SINCE 96 ALTHOUGH NOT OFFICIALY IMPORTED INTO THE UK BY
YAMAHA.
THERE VERY EASY TO DERESTRICT COMPARED TO THE OLDER VERSION.
THERE IS NO REEDSWITCH FITTED ON THESE BIKES , THE EXHAUST HAS NO RESTRICTION AS SUCH FITTED,
HOWEVER IT IS FITTED WITH A HOTCAT CATALYTIC CONVERTER THAT IS WORSE THAN THE OLD RESTRICTIONS.
IT IS REMOVABLE WITH DIFFICULTY , THE EXHAUST NEEDS CUTTING OPEN AT THE LARGEST PART OF THE
EXPANSION CHAMBER TO GET AT IT.
NO DOUBT THAT WHEN THE BIKE NEEDS ITS FIRST MOT TEST IT WILL NEED THE CAT, SO I WOULD JUST FIT A DEP
SYSTEM ETC. OR A DERESTRICTED EARLY MODEL EXHAUST , THERE SLIGHTLY DIFFERENT BUT FIT WITH VERY
MINOR MODS. ONE BRACKET NEEDS MOVING AND THE TAILPIPE NEEDS SLEAVING AS THEY ARE SLIGHTLY
DIFFERENT DIAMETERS WERE THEY JOIN THE MEET.
ALSO THE INLET MANIFOLD IS RESTRICTED IN THE SAME WAY AS THE 99 TILL 03 MODELS , JUST FOLLOW THE
SAME PROCEDURE FOR THIS. SEE THE PREVIOUS SECTION FOR DETAILS.
ALSO FOLLOW THE EARLIER PROCEDURE WITH THE BLACK PLASTIC BOTTLE FITTED TO THE AIRBOX TO CARB
RUBBER.

7. THE MAIN RESTRICTION ON THESE BIKES IS A REV LIMITER BUILT INTO THE CDI UNIT, BUT FORTUNATELY ITS
EASILY REMOVED ON THESE MODELS. GOING INTO THE SPEEDO IS A 4 WIRE CONNECTING BLOCK, THERE ARE
ONLY 3 WIRES ON THE SPEEDO SIDE OF THE CONNECTOR AND 4 WIRES ON THE LOOM SIDE. FIND THE
GREEN/BLACK WIRE ON THE LOOM SIDE OF THE CONNECTOR, SNIP IT FROM THE BLOCK, EXTEND IT AND CRIMP
AN EYLET ONTO IT AND EARTH IT TO THE FRAME VIA THE TOP RADIATOR MOUNT BOLT. THAT WILL REMOVE THE
REVLIMITER FROM THE CDI UNIT.
CHECK THE YPVS SYSTEM FOR CORRECT AJUSTMENT THE SAME WAY AS DESCRIBED AS FOR PREVIOUS
MODELS.
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YOU COULD CARRY OUT A RETRO FIT WITH EARLY TDR 125 PARTS BUT EVERY ONE OF THESE I HAVE
DERESTRICTED SO FAR HAS HIT 80 MPH SO I WOULD NOT BOTHER AS THAT’S ABOUT THE BEST YOUR GOING TO
GET FROM A DT125 WITH NO ENGINE MODS.
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