One idea at a time in focus mode
Nippondenso on the 122, SEM on the 123, the timing that is published, and the timing that is not.
Before you start
Your own risk. Wrong jetting or timing can seize the engine. This is information, not advice.
How many steps: 3
Step 1 of 3
A 122 ignition does not fit a 123.
Hartrusion and the research brief agree: the Rotax 122 uses a Nippondenso CDI, and the Rotax 123 uses a SEM magneto ignition. They are not interchangeable. Stators, coils and control units stay with the engine they came from. Hartrusion adds that later 122 bikes keep the same engine-side parts and use a different control unit, which he names as EFI Technology. What that box changes, compared with the earlier Nippondenso box, is To verify.
Step 2 of 3
Type 122 timing in degrees is not published.
Licence, MOT, insurance or a seizure.
Haynes does not print a Type 122 ignition timing in degrees. It stays To verify. Do not copy the Type 123 marks onto a 122. Type 123 static timing in Haynes is 19° / 1.84 mm BTDC. Hartrusion agrees with that static figure and adds a check at 10,000 rpm of 12° / 0.74 mm. The check is his, not a second Haynes figure. He also says the 123 has more advance from idle to 4,000 rpm than the 122, and that later 122 curves sit close to the published curve. The 122 degree figure is still not on the page. An ignition wedge appears in one exhaust comparison. Hartrusion says using it in that test made the engine knock, and he does not print the angle. The angle is To verify. This page does not tell you to fit one.
Step 3 of 3
No CDI pinout is printed on this site.
Derestriction notes name a Nippondenso retard around 5,000 to 6,000 rpm that varies by unit. They do not include a pinout, a wire colour or a solder bridge, and this page does not add one. Which ignition units left the factory with that retard is To verify on the unit.
This guide is done. Your place stays on this device.
Hartrusion and the research brief agree: the Rotax 122 uses a Nippondenso CDI, and the Rotax 123 uses a SEM magneto ignition. They are not interchangeable. Stators, coils and control units stay with the engine they came from.
Hartrusion adds that later 122 bikes keep the same engine-side parts and use a different control unit, which he names as EFI Technology. What that box changes, compared with the earlier Nippondenso box, is To verify.
Haynes does not print a Type 122 ignition timing in degrees. It stays To verify. Do not copy the Type 123 marks onto a 122.
Type 123 static timing in Haynes is 19° / 1.84 mm BTDC. Hartrusion agrees with that static figure and adds a check at 10,000 rpm of 12° / 0.74 mm. The check is his, not a second Haynes figure. He also says the 123 has more advance from idle to 4,000 rpm than the 122, and that later 122 curves sit close to the published curve. The 122 degree figure is still not on the page.
An ignition wedge appears in one exhaust comparison. Hartrusion says using it in that test made the engine knock, and he does not print the angle. The angle is To verify. This page does not tell you to fit one.
Legal and safety. Too much advance knocks and can seize the engine. A timing change is not a carburettor jet you can put back in five minutes.
Source: Haynes manual 4298, and Hartrusion’s ignition and exhaust pages
Derestriction notes name a Nippondenso retard around 5,000 to 6,000 rpm that varies by unit. They do not include a pinout, a wire colour or a solder bridge, and this page does not add one. Which ignition units left the factory with that retard is To verify on the unit.
Source: Derestriction guide, from the research brief and the blog it cites
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