It is the responsibility of the competitor to check his equipment (all components outside the engine seal as mentioned below), to assure that his equipment is conforming to the technical specification below.
Dellorto B11.1 Ignition Coil (same for all engine types) with Ignition separate Electronic Box (ECU, specific to the
System engine type).
B11.2 Ignition coil and electronic box have to be fitted by means of the corresponding brackets and components according to the illustration.
B11.3.1 The visual appearance of the ignition coil must be identical with the pictures.
B11.3.2 Ignition coil must show 2 pins at the terminal.
B11.3.3 The ignition coil is labelled with two stickers
“BRP 666820” and “NIG 0105”.
B11.3.4 The ignition coil is still legal to be used also if one or both stickers have disappeared.
B11.3.5 Minimum length of ignition wire (high tension wire) is 210 mm from outlet of cable at ignition coil to outlet of cable at spark plug connector (the visible length of wire).
B11.3.6 The earth strap may be fitted with a connector for ease of removal of the engine. Rotax Wiring Harness must be OEM only, with no fittings or repairs.
TECHNICAL SPECIFICATIONS – JUNIOR (MICRO) – (A) FR 125 MAX (NON EVO) OR (B) FR 125 MAX (EVO) 029600-0710, followed by a variable production code in the 2nd line (Image 3).
The electronic boxes are labelled with stickers (specific to the engine type) and are still legal to be used also if the sticker has disappeared.
125 Junior Max EVO: “666812” and
“125 Junior MAX evo”
The electronic box has to be checked with the ECU tester (Rotax part no. 276 230) according to the following procedure:
1. Disconnect engine cable harness from electronic box.
2. Connect ECU tester cable harness to electronic box.
3. Connect energy cable of ECU tester cable harness with the chargin connector of engine cable harness.
4. The ECU tester will automatically detect the type of the ECU and will start a check program for the ignition timing and the timing for the exhaust valve.
5. The ECU tester must show the following results for 125 Junior Max EVO:
“ECU TEST OK”
“125 Junior MAX evo”
Centrifugal Clutch
B13.1 Dry centrifugal clutch with engagement maximum at 4,000 r.p.m.
This means that the kart must start to move before the engine speed reaches
TECHNICAL SPECIFICATIONS – JUNIOR (MICRO) – (A) FR 125 MAX (NON EVO) OR (B) FR 125 MAX (EVO)
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B13.2.2 O-Ring 12x2.5 (Rotax part no. 950 815) must be fitted and must assure an appropriate sealing between the clutch drum and the needle/plain bearing.
B13.3 No extra lubrication or substance is allowed inside the clutch drum, in addition to the grease that originates from lubrication of the needle cage bearing, and enters the clutch area.
See (Images) showing worst case scenario of when grease exits the needle bearing area, even with the O-Ring installed. Only the fixation nut and the inside of the drum show signs of grease. The running surface of the drum is completely dry.
When the plain bearing for 11 tooth sprockets is used, the clutch area must be absolutely free of grease or any additional substance.
B13.4.1 Steel clutch (both versions) and clutch drum must be within the following specifications:
B13.4.2 Height of clutch: Minimum = 11.45 mm
B13.4.3 Thickness of clutch: Minimum = 24.10 mm NOTE: Measurement has to be done at the 3 open ends of the clutch shoes, 5 – 10 mm from the machined groove (all clutch shoes must be completely closed at measurement, with no gap showing).
B13.4.4 Outer diameter of clutch drum:
Minimum diameter = 89.50 mm
NOTE: Diameter has to be measured with a sliding calliper, just beside the radius from the shoulder (not at the open end of the clutch drum).
B13.4.5 Inner diameter of clutch drum:
Maximum diameter = 84.90 mm
NOTE: The inner diameter has to be measured with a sliding calliper. The measrement has to be done in the middle of the clutch drum (in the contact area of the clutch drum).
TECHNICAL SPECIFICATIONS – JUNIOR (MICRO) – (A) FR 125 MAX (NON EVO) OR (B) FR 125 MAX (EVO)
B13.4.6
B13.4.7
Height of sprocket with clutch drum assembly:
Minimum height = 33.90 mm
The original Rotax clutch (3 spring) is eligible to be used at any event until further notice.
Intake
Intake silencer with integrated, washable air filter has to be used with all parts as shown in the illustration and has to be mounted on the support bracket with two screws (in dry and wet
condition).
Intake Silencer case bottom is marked on .the inside with the Rotax part no. “225 015”
Intake Silencer case top is marked on the inside with the Rotax part no. “225 025”.
Air filter must be installed as shown in illustration.
The original square type intake silencer is not eligible to be used for Rotax National Series, State Championships or events where Rotax is run as a standalone class. It can be used in Restricted TAG, TAG and Sportsman style classes.
Carburettor B15.1
B15.2 B15.3
B15.4
Dellorto carburettor with “VHSB 34” cast in the housing of the carburettor.
“XS” is stamped in the housing of the carburettor.
The complete inlet bore in the casting of the carburettor must show a cast surface.
Jet needle stamped with “K57” only.
TECHNICAL SPECIFICATIONS – JUNIOR (MICRO) – (A) FR 125 MAX (NON EVO) OR (B) FR 125 MAX (EVO)
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B15.7 All jets must be correctly seated and securely fitted.
B15.8 A minimum required size of Main Jet may be determined for each race event by a
“Supplementary Regulation”.
B15.9 Needle Valve assembly stamped with the digits
“150” (Image 1)
B15.10 Needle of Needle Valve marked with diamond symbol “INC” only (Image 2).
B15.11 Start Jet is stamped with the digits “60”.
B15.12.1 Needle Jet is stamped with “DP 267”.
B15.12.2 Total length of Needle Jet = 51.00 +/- 0.3 mm
B15.12.3 Length of bottom section of Needle Jet
= 33.0 +/- 0.2 mm
B15.13.1 Idle Jet 60 and Idle Jet Insert 45 must be used with carburettor insert stamped 12.5, as per illustration at rule B15.15.1.
B15.13.2 Plug gauge 0.65 mm may NOT enter the bore of the Idle Jet 60.
NOTE: Use jet gauge set (Rotax part no. 281 920)
B15.13.3 Plug gauge 0.55 mm may NOT enter the bore of the Idle Jet Insert 45.
NOTE: Use jet gauge set (Rotax part no. 281 920)
TECHNICAL SPECIFICATIONS – JUNIOR (MICRO) – (A) FR 125 MAX (NON EVO) OR (B) FR 125 MAX (EVO)
B15.13.4 Plug gauge 0.55 mm may NOT enter one of the 4 cross bores of the Idle Jet Insert 45.
NOTE: Use jet gauge set (Rotax part no. 281 920)
B15.14 Carburettor insert must show stamping of 12.5, as illustrated.
B15.15.1 Remove atomizer from the carburettor body using the Venturi Tool Set (Rotax part no. 676 034).
Total length of atomizer = 23.75 +/- 0.45 mm
B15.15.2 Length of cylindrical part of atomizer
= 15.75 +/- 0.25 mm
TECHNICAL SPECIFICATIONS – JUNIOR (MICRO) – (A) FR 125 MAX (NON EVO) OR (B) FR 125 MAX (EVO)
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B15.15.4
B15.16.1
B15.16.2
Diameter of cross bore of atomizer
= 5.00 +/- 0.15 mm
Optional carburettor plug screw marked “ROTAX”
(Rotax part no. 261 030) is legal to be used.
The two vent fittings must be connected with the original 180mm air vent hose.
(Rotax part no. 260 260).
Fuel Pump B16.1 The original MIKUNI Fuel Pump (diaphragm type) must be used.
Single aluminium radiator, as shown in illustrations below.
Radiator must be mounted on the right side of the engine, with all components as shown in the respective illustrations.
No additional non-original cooling device is allowed.
The removal of the thermostat from the cylinder head cover is accepted.
For versions 1, 2 and 3, tape can be applied around the radiator. Tape may not be removed from the radiator during operation on the track. All other means of air flow control through the radiator are prohibited, except for the plastic flap on version 3.For version 3, the removal of the original plastic flap is accepted.
Version 1
Cooling area: Height = 290 mm, Width = 133 mm Thickness of radiator = 32 mm
TECHNICAL SPECIFICATIONS – JUNIOR (MICRO) – (A) FR 125 MAX (NON EVO) OR (B) FR 125 MAX (EVO)
Version 2
Cooling area: Height = 290 mm, Width = 133 mm Thickness of radiator = 32 mm
Version 2 has two legal options to mount the radiator to the retaining plate (see illustration).
Version 3
Cooling area: Height = 290 mm, Width = 138 mm Thickness of radiator = 34 mm
The word “ROTAX” is stamped on the side of radiator.
Radiator Coolant
B18.1 B18.2
Glycol base or soluble oil coolants are prohibited.
Radiator coolant system must be fitted with a catch tank of minimum 100mL capacity to retain radiator coolant overflow, in accordance with Technical Rules Chapter1 Rule 9(h)(iii) 2
Exhaust B19.1 Must be as supplied by BRP-POWERTRAIN and System cannot be modified except for the replacement of
the silencer absorption material and the use of threaded fasteners in place of the original rivets for securing the silencer end cap.
B19.2 Just one piece of standard isolation mat is allowed to be used. Can only be replaced with genuine spare part (Rotax part no. 297 981).
B19.3.1 Additional to the standard isolation mat is a special steel isolation mat which is legal, but not
TECHNICAL SPECIFICATIONS – JUNIOR (MICRO) – (A) FR 125 MAX (NON EVO) OR (B) FR 125 MAX (EVO)
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B19.4.1 The only exhaust pipe legal to be used is the version where the 180o elbow and silencer are
1
two separate pieces. The silencer is fixed with two springs to the 180o elbow and two springs to the tuned pipe (Image 1).
B19.4.2 The silencer can be rotated so that the 90o elbow outlet of the silencer is pointing either downward towards the asphalt (preferred for lowest noise emissions) or upward towards the back.
B19.5 For measuring the exhaust gas temperature, a weld on a socket on top of the exhaust, 50 mm from the ball joint is allowed.
B19.6 Exhaust socket with gasket ring only is legal to be used (Image 2). Measurement (C) must be at least 15.5 mm
B19.7 The maximum use of exhaust springs to fix the
exhaust to the cylinder is 4 springs.
2
TECHNICAL SPECIFICATIONS – JUNIOR (MICRO) – (A) FR 125 MAX (NON EVO) OR (B) FR 125 MAX (EVO)