Honda CRF 300 L ECU swap

Crawling along a slow technical trail on this bike is hard. Or maybe a correct way to put it would be, that it is not as easy as it should be or could be. This is due to the fact that the throttle has a severe on/off tendency at low speeds / low revs.

At the root of the problem (I believe) are the Euro 5 emissions standards and as such the problem might not even be fixable legally in some countries. That said, I believe there is a solution out there.

Fist attempt (not a working solution)

My first “fix” was to adjust the throttle freeplay in order to have better control over the throttle. This worked a tiny bit, but does not address the actual problem.

(see ->

The CRF 300 L ecu can be found under the left fairing

Second attempt (in motion)

Why not get a factory ECU from a market that does not need to adhere to Euro 5 standards? With this in mind I ordered a Thai ECU and plan on giving it a go and see if it fixes the issue.

I’ve seen reports of Thai ECUs resulting in error codes on the dash, but I’ve also read people using them without issues. How the Thai ECU works for your bike, might depend on what kind of ECU your bike is running from the factory and/or what market your bike is made for. Bikes seem to have small differences depending on where they are sold, EU, USA, Japan and so on.

Would be interesting to know how many different ECUs there are for this bike and what are the actual differences.

I`ll keep you posted on how this turns out.

UPDATE 23rd Sept. 2021

Well… this did not work out either. The Thai ECU is a completely different unit from the Euro version. Apparently the Thai ECU is interchangeable with the USA ECU, but certainly not the Euro version.

Given that the reflash is based on the Thai unit, that option is off the table too. The full stand version will most likely not work either.

Honda CRF 300 L Thai ECU (left) and Euro ECU (right)
connectors are very different too

Honda CRF 300 L euro ECU

Third attempt (not in play yet)

If the Thai ECU experiment fails, there is at least one more viable option. That is to reflash the second ECU with settings aimed to alleviate the issue. In all honesty, this should have been done as the second attempt, but I found about this possibility after I had ordered the Thai ECU.

550 Performance is the only one I have found so far that does reflashing for CRF 300. They only seem to have Facebook page.


Because the US/Thai ECUS are different, it is unlikely that 550 Perfomance is an option if you have a Euro bike.

CRF 300 ECU versions

There are no doubt several versions out there. So far I’ve seen proof of 4 different ones:

  • Thai, ending in T01
  • EU (Fin), ending in E11
  • USA, ending in A11
  • Canada, ending in C11
  • Australia and NZ ending in H01 (same size as the US/Thai version)

Fourth attempt (not in play yet)

There is also this thingy called Full stand Next (
From what I understand, it’s device that piggybacks the ECU and is programmable via an app.

The website does not list one for the CRF 300 L, but the videos clearly show that there is such a thing. The manufacturer doesn’t seem to actually sell these and I could not find I retailer that I could actually buy one.


Because the US/Thai ECUS are different, it is unlikely that 550 Perfomance is an option if you have a Euro bike.

It may be illegal in your country to swap or reflash an ECU. Swapping the ECU may also void the warranty.


(UPDATE 19.11.2021). I’ve now heard that the EJK works fine with the Euro ECU and actually does help with the snatchy throttle. No personal experience yet.

[UPDATE 11.12.2021]
I installed the EJK. No riding experience yet. I will update progress in here:

17 Comments Add yours

  1. Wasin Intasarn says:

    Here in Thailand. It’s very easy to buy FullStandNext from Thai’s online marketplaces such as Shopee or Lazada.
    You can chat with the retailer if they can ship it to your country.

    Liked by 1 person

  2. FG says:

    I’m EU and ordered thai ECU38770-k1t-t01. Unforunately a completely different size unit (smaller) and connector.


  3. Iain Harris says:

    Another ECU version to add to your list is 38770-K1T-H01 which is the unit fitted to NZ and Australia bikes. It’s the same size as the Thai unit.

    Liked by 1 person

  4. Any chance to get the wiring with the connector from the Thai model and try rewiring on your EU version? Kind of tricky, I know, but maybe the only solution…

    Liked by 1 person

  5. Richard Challis says:

    Unfortunately I feel your pain having done all of the exact same work! 550 performance did send me a cable and Honda ECU SW to plug in via the diag port under the tool box lid, but I could not get it to communicate. This needs resolving as there is a Market for this!! I agree the on/off throttle is a nightmare..

    Liked by 1 person

  6. Álvaro Javier Fernández Zamora says:

    Do you think the EJK for the 300 L would solve the problem?
    Thank you for your comments


    1. JN76 says:

      I don’t know. I haven’t heard / read anyone using EJK in combination with the Euro ECU.


  7. Álvaro Javier Fernández Zamora says:

    In a few days I will have It at home.
    I Will tell you something as soon as I install it and test the bike.
    By the way, I live in Spain.
    All the best


    1. JN76 says:

      Great! I’m very interested in hearing how it works.


      1. Álvaro Javier Fernández Zamora says:

        Hi there,
        I already intalled the EJK and test the bike in all different situations, from fast open tracks to very technical single tracks and I have to tell that the bike is perfect now. No more on off throtel response at all. It IS really smooth and no more nightmare with that.
        Keep in mind that my bike IS sold in Spain. I took the reference of the Ejk from CRF,S ONLY and bought It in the Netherlands from G and G bikes ( 250€).
        I hope to have been helpfull.
        Sorry about my English.
        All the best

        Liked by 1 person

      2. JN76 says:

        Thank you for this info!


  8. billou06 says:

    Thank you Alvaro for this info, I have been looking for a good time to fix this nightmare accelerator “ON / OFF”. Can you confirm that you ordered the EJK MFG P / N 9110044 model?
    The installation did not ask you any problems?
    Thank you for the information you can bring me
    Sorry for my disastrous English … 🙂 (I am French)
    Looking forward to reading you …


    1. JN76 says:

      Yes I did order one, but they were out of stock so I don’t have it yet. I will make a post once I get it.

      Liked by 1 person

      1. Álvaro Javier Fernández Zamora says:

        It IS a bit hard to unplug and plug the one beside the cilinder but other than that no problem at all.
        Bon chance

        Liked by 1 person

    2. Álvaro Javier Fernández Zamora says:

      I actually ordered the one ending in 35 and changed the adjustment to the one ending in 44 acording to the EJK web site and IS working perfect,so, yes, The one ending in 44 IS the right one. Visit the Ejk web site so that you are sure.My English IS not perfect either since I am Spanish

      Liked by 1 person

  9. tomka says:

    Great content buddy! Keep up the good work you do for us! Tom

    Liked by 1 person

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