1993–2006 · two-stroke
Every item below names where it came from and how far it has been checked. A number that is not in a source is not invented to fill the gap. Haynes figures stay labelled as Haynes figures.
The reliable setup is the one in the workshop manual for the engine you actually have. These are the checks the sources already support.
MCN’s maintenance note, via the research brief, is to reach 60°C before hard riding. That is a riding habit.
Haynes 4298 says the thermostat begins to open at 70–75°C, with 3.3 mm of lift at 90°C. Those are different facts. A cold two-stroke is how a fresh top end tightens.
Rings around every 5,500 miles. Piston and barrel around every 10,000 miles. Those are planning figures for the two-strokes, not a measured wear limit.
The wear limits Haynes prints — piston codes, ring gaps, bore service limits — are on the engine specs page. Do not substitute a forum piston.
Source: MCN, via the research brief
Hartrusion records different carburettors, ignitions, clutches and internals. Cylinders, gearboxes, gaskets and cranks do not swap.
A replica decal kit does not change which engine is in the frame. Read the casting.
This is a description of how these bikes were restricted. It is not permission to ride an opened two-stroke on an A1 or provisional licence.
GOV.UK sets A1 at up to 125 cc, 11 kW and 0.1 kW/kg, from 17. After a CBT: L-plates, no passenger, no motorway.
Open two-strokes in the research brief are about 21–23 kW and need an A2 or a full A. MCN’s separate sentence is that anything above the restricted 15 bhp is illegal on a provisional or A1 licence. This site does not treat 15 bhp and 11 kW as the same limit.
Legal and safety. Changing the restriction does not change the licence you hold. Tell the insurer. The wording each policy wants is still To verify with that insurer.
Source: GOV.UK licence categories, and MCN via the research brief
The brief’s steps name a powervalve blanking plate instead of the RAVE blade, a Nippondenso retard around 5–6,000 rpm that varies by unit, a catalyst in the expansion chamber from 2003, and a jet and plug change when the pipe changes.
This site does not publish a CDI pinout or a solder bridge. Which codes left the factory with a plate is To verify on the bike.
Legal and safety. Removing a catalyst and riding the bike is an emissions and insurance question as well as a tuning one. Do not assume an MOT tester or an insurer will treat it as invisible.
The valve, the cable, the solenoid and the controller. Clearances for the blade itself are not published.
The generation record names a stuck powervalve and a seized solenoid on the bee-tail. Look before you buy, and again before you blame the carburettor for a flat spot.
Haynes 4298 gives RAVE cable free play of 0.5 mm and valve bolts of 10 Nm. The control-unit test pairs are on the electrics page. The connector pinout is not published.
The derestriction steps say the blade goes in taper down, flat side up. That is one written account in the research brief, and the guide still says to confirm it in the manual for the year before the cover is locked.
A restricted bike may have a blanking plate where the blade should be. The Extrema / GS had no factory-restricted version, per Hartrusion in the brief, so a plate on one of those has been added.
Legal and safety. Fitting the blade on a bike that must stay at 11 kW or 15 bhp is a licence problem, not a weekend improvement.
These engines pump oil. A single premix ratio is the wrong kind of number, and Haynes 4298 does not print one.
Hartrusion says the owner’s handbooks give 0.9% to 2% on the older Rotax 123 and 1% to 3% on the Rotax 122. The amount moves with rpm and with how far the twistgrip is open, so one ratio such as 50:1 is not a setting.
The 123 pump is stamped 08. The 122 pump is stamped 33. They look alike and they are not interchangeable: the piston diameter and the drive ratio differ.
The worm drive is 1:35. With the rest of the drive, Hartrusion calculates about one stroke every 50 crank revolutions, and at idle a small shot about every 3–5 seconds.
Hartrusion describes bleeding at the small screw on the pump until the oil runs without air. Do that after the tank has been empty or a line has been off.
MCN’s grade note is a premium two-stroke oil in the tank. Haynes 4298 does not name a grade code. An empty oil tank will still let the engine run, until it does not.
Legal and safety. A seized engine from a dry oil tank is a safety failure, not a tuning result.
Source: Hartrusion oil-pump page, and MCN via the research brief
The manual’s PHBH28BD stacks are the figures to start from. A forum chart that uses different jets is kept as a dispute, not as a second baseline.
11 kW: starter 70, main 115, pilot 62, needle BN 264, float needle valve 250. 20 kW column: starter 70, main 120, pilot 62, needle BN 266, float needle valve 250. Idle 1,150–1,350 rpm.
Haynes lists that carburettor for both columns. It does not give a stack for the 34 mm VHSB the research brief records on the Rotax 123. Do not put these jets in a 34 mm body.
The plug in the manual is an NGK BR10EG, gap 0.5–0.7 mm. A blog also names a BR8EG. The manual extract does not.
Legal and safety. A jet change that goes with an opened pipe can take the bike out of the power it was insured and licensed as. Tell the insurer.
Source: Haynes manual 4298
An ApriliaForum thread reprints a translated chart with different pilots, needles and plugs, including a pilot of 65 and an NGK BR8ES. Haynes 4298 prints pilot 62 and a BR10EG.
That chart is not used on this site as a specification. It is here so it is not mistaken for the manual. Pilot-screw turns, float height and needle-clip position are not in Haynes 4298.
A 125cc Sportsbikes thread describes a preferred air-screw window of about 1 to 2 turns out as a way to judge whether the pilot is lean or rich. That is a tuning method from one thread, not a factory baseline.
The RS 125 blog says to set float height at 14 mm. Haynes 4298 does not print a float height. The “250” in the manual is the float needle valve size, not a height. One blog is not enough to publish 14 mm as the specification.
The thermostat specification and the riding warm-up are both kept, because they measure different things.
Thermostat begins to open at 70–75°C. Maximum lift 3.3 mm at 90°C. Coolant is about 0.9 litres, half distilled water and half ethylene glycol antifreeze for aluminium engines.
The temperature sensor Haynes lists is 1 kΩ at 20°C, 50 Ω at 90–95°C, and 15 Ω at 120–130°C. Where that sensor is screwed in is still To verify.
The cooling-system bleed procedure is not in the photographed Haynes pages used here. To verify.
Source: Haynes manual 4298
Charging figures and the two ignitions are published. A regulator failure story is not, until someone sources it.
Battery 12 V, 9 Ah. Regulated output 13.5–15.0 V at 6,000 rpm. Type 122 unregulated output 53 V AC at 6,000 rpm. Type 123 unregulated output is not published.
Stator resistance is 0.1–1.0 Ω on the 122 and 0.2–0.4 Ω on the 123. Fuses: lighting and instruments 15 A and/or 20 A, ignition 7.5 A.
Source: Haynes manual 4298
The research brief and Hartrusion put SEM ignition on the Rotax 123 and a Nippondenso CDI on the 122. SEM stators are the scarce part. They do not belong on a 122.
The brief describes an environmental retard around 5–6,000 rpm and says the detail varies by unit. No wire colour is published here.
Haynes and Hartrusion agree on the 123 static figure: 19° and 1.84 mm before top dead centre. Hartrusion also gives a check of 12° and 0.74 mm at 10,000 rpm, and says the stator is held in slots so it can be moved.
Hartrusion says the 123 has more advance from idle up to 4,000 rpm than the 122. A degree figure for the 122 is still not published. Do not copy the 123 marks onto a 122.
Source: Haynes manual 4298, and Hartrusion’s Rotax 123 ignition page
A failure mode, a part number, and a test beyond the regulated-voltage figure above are not in the sources used here. To verify. Do not replace a regulator because a forum thread blamed one on a different bike.
Source: No source yet. The charging figures that do exist are on the electrics page.
The RSV-style generation record names immobiliser trouble. Keep both keys. Cutting the immobiliser out of the loom is not a repair this site describes.
Source: RSV-style generation record
Taken from the generation records. This is not a complete fault list.
Starter freewheel and flywheel ring gear. Mechanical tacho drive. SEM stator. Discontinued 123 parts.
Source: Extrema / GS generation record
The wrong engine in the advert. Scarce 123 parts. Clocks that fail.
Source: Round-light generation record
Catalyst from 2003, CDI flat spot, stuck powervalve, worn speedo drive, crank bearings, rotten exhaust.
Source: Bee-tail generation record
Immobiliser, exhaust corrosion, and the bee-tail engine faults. The frame is still the MP frame, so a claim of a new chassis is wrong.
Source: RSV-style generation record
Measurements the manual already prints. They cost a ruler or a torque wrench, not a new engine.
Chain is size 520, slack 25–35 mm. Pad friction material minimum 1.5 mm in the workshop manual. That is stricter than the MOT’s dangerous line, which is a lining below 1.0 mm.
Look in the oil tank every time you look at the petrol. RAVE cable free play is 0.5 mm. Clutch lever free play is 10–15 mm. Throttle and choke free play are 2–3 mm.
Source: Haynes manual 4298, and the DVSA brake section for the 1.0 mm line
Special tool numbers are not published in the pages this site has. Buy the tool the manual names, not a near fit.
A torque wrench covers the fastener list. A flywheel puller, a fork-seal driver and a dial gauge for the 123 timing are the jobs that need the right tool. The tool numbers are To verify.
Hartrusion says the 123 plug-hole thread is the usual M14×1.25, and describes finding 1.84 mm with a dial gauge. That is a pointer to that page, not a copied procedure.
Source: Hartrusion ignition page. Tool part numbers are not on this site.
The short list the sources actually support. Anything else is To verify.
An empty oil tank. A 123 part forced onto a 122, or the reverse. A catalyst or a restriction removed while the old jets stay in, which the derestriction notes name as how these engines seize.
A seized RAVE that you then force. A balance shaft assembled on guessed marks: the tooth marks are not published, and one tooth out is chased for months as a carburettor fault.
Legal and safety. An engine that has been opened past the restricted specification can be illegal to ride on the licence you have, and it can be outside the insurance you bought. Read the UK law page first.
Source: Cooling guide, Hartrusion, the derestriction notes, and the bottom-end guide
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