Euro 5

[Islay4000]

I’ve recently bought a 2022 Kymco AK550 and overall I’m very pleased with it. However, there’s one issue that’s spoiling the low‑speed experience: the on/off throttle response at small openings, which makes the bike feel jerky when riding slowly, especially in traffic.

From what I’ve learned, this seems to be caused by the Euro 5 fuel cut‑off behaviour, where the injectors shut down completely on a closed throttle and then snap back in when you reopen it.

Has anyone else experienced this on their AK550, and if so, did you find any effective workarounds or modifications that help smooth out the low‑speed throttle response?

[roadster]

Sorry to hear about this. My early model AK550 didn't suffer from it so you may well be right about changes being introduced due to later regulations. There are various devices which intercept the oxygen sensor and fool the ECU to some extent, and you may be interested in this :-
https://youtu.be/96Kx2cYPOdQ?si=8wK_ycE-ZrTIWEo6

Personally I would research this and similar devices very carefully because its all to easy to make a box with flashing lights and charge lots of money for them!

[Islay4000]

Thanks for your feedback. Using A.I. yes it often tells you what you want to hear but sifting through the mountains of often contradictory information I concluded the only solution that works is remapping. I have been in contact with http://www.hilltopmotorcycles.co.uk/ they offer a service where you take the bike to them, they remove the ECU and install a modified map.
My present issue is the ECU is tucked away on the left fork leg, I can’t figure out how to remove the panel to get access, the official workshop manual is vague to put it mildly, any advice would be welcome.

[Andym]

Is it Euro 5 or 5B?

There is a difference. What Google AI describes as "OBD thresholds" is a raft of changes related to UNECE R155 and R156, respectively cyber security and prevention/monitoring of unauthorised changes. What you don't know is how any manufacturer has met these requirements. In my world, commercial vehicles, they have variously locked and included reactions to "tampering". The locks when broken generally brick the ECU. The "reactions", usually triggered by contact with a connected diagnostic tool, are to return the ECU to approved settings or lock a warning light until they are.

Make sure anyone flashing the ECU can convince you they understand this. What works when you collect can stop working next time a workshop or the RAC connects.

Defeat devices likewise must be considered, but at least it's a clear accept or reject, fit or remove. The ECU just thinks you are riding on Venus, there is no check checksum or signed file to prove tampering so it keeps trying. Defeat devices however are generally made by hobbyists so not true Automotive quality.

Have you spoken to Kymco? There is no reason for such crude settings and many manufacturers have responded with updates. If they have an update in development, that will be the best choice by every measure from cost to longevity.

Andy

[Islay4000]

You’ve raised some useful points. As I understand it, the process doesn’t overwrite the existing map but instead installs a new map into free memory on the ECU. That gives me several questions to follow up on regarding how the installation is handled and whether future access via the OBD interface is affected.
Regarding going back to Kymco I am looking into that.

[Andym]

Future access should not be changed in terms of reading faults.

The rest is going to vary with what the Kymco ECU is and what the "hacker" does;

Usually you install a hex file. The code has to replace whatever was there before or the ECU detects is a checksum error and just faults the lot, bricked until it's happy. The idea of a memory and the ability to switch back and forth is silly, until you meet a different logic at the manufacturer. Let's say Scania offer a 350HP and 500HP tractor unit. They don't want two part numbers, so yes, they park both lots of settings in one ECU and something chooses left or right, probably an EOL tool with coded but not fully restricted access. The hacker can switch on the 500HP settings without the upgraded con rods and it gets crunchy if not turned off again, but the owner is happy they got the big power at the smaller price until it does. The hacker could also overwrite the 500 HP settings with an extra pollution/"smoother" 357 HP version and go back and forth via a reverse engineered EOL tool/stolen PIN whatever they developed.

I wouldn't expect Kymco to need another set of settings in their ECU, but maybe they do and you'll lose the theoretical ability to switch to a restricted version for learners in Switzerland or something.

Faults are read out, you aren't asking for anything to change at the higher level.

This whole industry should be squashed very firmly by UN ECE R155 and R156 which landed in 2022-24 for cars. This requires bank level security not the sort of "add the VIN number to every entry" level the tuners could break in minutes (and some manufacturers almost encouraged). If you are getting something chipped, do it now because in a few years all the companies doing it could be gone and there will be no one left to help when older modifications go wrong.

Andy

[John A]

I'd be looking at the Power Commander of Booster Plug options.

I had a few bikes where you had to learn to not fully close the throttle as then the jerkiness was very much reduced, a right PITA tying to unlearn decades of muscle memory.

[Andym]

We'll see what happens with Power Commander etc. They are cheat devices, so after the VW debacle are on the radar. There is no reason the vehicle can't detect them and at least pop the light, which is now an MOT fail. The legislation says "all reasonable measures" which is then a debate between manufacturer and technical authority. It'd be easier if they just did their job and make compliant engines that meet market desires. I doubt they'll go away, lots of snake oil marketing, so they'll still have the stand next to the gearbox PTFE loons and petrol catalyst nutters at all the shows.

Andy

[Ralph]

His there a procedure to reset the throttle position sensor? if so could it be that?
this can be done using the onboard diagnostics on some scooters, others have
a first use setup procedure ie start it and let it idle till the fan cuts in or some such
allowing the ecu to learn settings, has this been done.

Edit apparently you can recalibrate the TPS

https://www.bing.com/videos/riverview/r ... &FORM=VIRE