Here you will find instructions, collected tips and tricks for the Aprilia RS 125. The content of this page is mostly the result of many hours of repair and work and is aimed at all motivated mechanics who have similar questions about this bike.
This is a translated version of the original site and always work in progress (Nov. 2019). Everything that is linked is translated and everything that is not isn’t. Most of the text is translated with help of the DeepL translator, so if there is anything named totally wrong please contact me.
This page is not connected to the manufacturer in any way and is operated and maintained by a private individual. Please read the disclaimer and notes.
I am always open for suggestions, questions and qualified feedback by using the comment function.
- What to know about the RS 125
- A guide for buying a used bike
- Differences between Rotax 122 and Rotax 123
- Maximum Speed Table (vmax)
- Engine warming-up
- Dethrotteling and unrestricted bike
- Differ Rotax 122 and Rotax 123 from the outside
Repair and Workshop Tips
- Enginge not starting – what to do now?
- Common problems with low engine power
- Using the right gearbox oil (Avoiding clutch problems)
- Power Valve (RAVE)
- Installation of compensation shaft gears in Rotax 123
- Bearings and gaskets for Rotax 122 and 123, proper removal of crankshaft bearing
- Function and diagnostics on the SEM ignition on the Rotax 123
- Rotax 123 Gearbox Assembly
Good to know for self-repair
- Reset Service display (RS 125 after Bj. ’06)
- Compression Ratio and Compression Pressure
- Overview: Electronic Control Units
- Remove Power Gap from 071000-0910 QCA91
- Carburetor Setups for Dell Orto PHBH 28
- Carburetor Setups for Dell Orto VHSB 34
- Stage6 Exhaust Gas Temperature Meter
- LED Turn Indicator Lights
- Installation Manual for Domino short stroke thottle handle
- Tuning Manual
- Polini 154 cm³ big bore test
- Pneumatic RAVE2
For more tips, help and for further questions I have put together a link list with some websites where you can get further help.
- Recommended Links
Please note that I do not carry out any contract work and I will not repair other people’s motorcycles. Inquiries about this via the contact form are of no use and will always be answered with a reference to the nearest specialized workshop.
Disclaimer and notes
Any liability for any damage that may result from the instructions and data published here is generally excluded.
This site is not intended as a substitute for specialized workshops and will never make this claim. A competent consultation by experienced motorcycle mechanics can never be replaceabled by any internet webpage!
Anyone who carries out work on vehicles themselves needs more than instructions from the Internet as you can find them here: Experience, specialist knowledge, high-quality tools and suitable premises. Such things are a prerequisite which is not dealt with in detail here every time, but which are usually available in specialist workshops.
Saving the money for the professional workshop for purely financial reasons and instead working in a dusty shed with worn out cheap tools is not only a bungle but a life-threatening bungle, also for other road users.
I owe a considerable part of the knowledge and my experiences that I share here to people who have shared this with me and wide parts of the internet.
In particular, in Apriliaforum.de these were besides the great team Persilia, DellOrto, Kojo125, Mooserider and many others. Thanks to everyone in the German Two-Stroke-forum, especially moe589, for what is readable and freely available for everyone there.
A special thanks goes to my father for not just putting me in front of the TV as a child (as it is common today) but taking me with him to his workshop.
Why the RS 125?
When I was 18 when I got my motorcycle driving license, it was limited to 34 hp for the first few years, so an unrestricted RS 125 fitted well for the beginning. That was 2007. As a moderator under the nickname “sonic.noize” I was able to make a name for myself on Apriliaforum.de, had a website and worked myself relatively deeply into the topic. Since the whole pages (sonic-rs.de as well as Apriliaforum.de itself) are offline now, I dug up the old slats again and put them online again – maybe it’s still of interest for someone.
After a few years, I became less and less interested in the topic. I’ve always been fascinated by technology, precise work is kind of satisfying but loud exhaust systems and a life for the leaning position didn’t appeal to me as much, I could enjoy nature better on the bike.
As a motorcyclist you unfortunately have a hard time when you can’t get anything out of empty rear silencers (that’s just ruthless, it’s unbelievable when you unfortunately live next to such a popular road) or just don’t want to heat up like a madman around curves that are hard to see. I always found restored vintage cars more fascinating than worn tyres. Also the tone in some internet forums was too outrageous for me at some point, which is why I withdrew almost completely from this topic. Everybody knows everything best, does everything right, everybody else is a retard and has no idea and is insulted in general.
However, I still like to work on machines and engines, nobody can take this fun away from me, and I am a convinced two-wheeled cyclist – especially in times when cars are getting bigger and bigger. Effective technology fascinates. While the big SUVs, which are unfortunately in use today, need far more than 10 litres per 100 km, the small RS4 125 still does it with less than 3 litres/100 km.