2023 KTM 125SX 250sx 300sx deep dive EFI tune, mods, mapping, exploring the tech *YoutTube videos added* *Facebook Group added*

Has anyone tried dielectric grease on their electrical connections.  Thinking this could help on the washing issue.  We just purchased our new 125.  No issues yet just over 2 hrs and same plug 

Wow thank you for this thread and the work you are doing. I just bought 2023 125 for my son. Im concerned about the issues you discuss. Hes a newer rider and it was only until this thread that i asked him if he experienced any issues and he said rpm drops a couple times. Weve been running on green noooooo! 
 

if you were me, what upgrades/changes would you do? Have john ross do the ecu? Should i first take to dealer and have them verify tps 0.40v and set perfectly if not? 
 

Any direction will help us a ton! Sam

Thank you! We just switched to white map and took it out. It was excellente. Im going to take into dealer for map update. Having a drop in would be killer, but no! Haha. 

quick question 
which piston are you using ? which one have you tested ?

Thanx

Jbone, thank you for all the effort you've put into this thread and the video series about this bike!

Before i ask my question, i want to offer what we've learned so far:  I bought my son a '23 KTM 125 XC last month. He has 11 hours on it now. The plug fouled at 2 hours. After switching to an NGK BR9ECMIX and gapping it at .024", we haven't had another plug failure. He is able to ride in both maps now without issues.  I have him using the white map for slower trail riding, and the green for motocross tracks or faster trails. The IX is the Iridium version, as compared to the original VX Platinum plug. Auto Zone stocks the BR9ECMIX plugs for $11.99.  From my understanding, there is no disadvantage to using an Iridium plug versus a Platinum plug. Normally Iridium plugs cost more, so maybe that is why KTM went with the Platinum plug, to save a buck on production costs.  After the latest service bulletin updates referenced down below are complete, i will go back to the stock 10 heat range plug, and see how it works with the latest ECU settings and other updates KTM has recently issued. We run 40:1 per the manual, with just ordinary premium pump gas. I've tried Motorex premix oil and Maxima Super-M because we had a bunch of Super-M and i wanted to try it.  So far, the bike runs exactly the same with both of those oils.

My question is about your piston cracking comment. Have you cracked a piston on your '23 125 SX? Please elaborate if you can. Where was the crack located? I also have a bore scope and much of the piston can be seen with that and also removing the pipe and reed valve. If you can pinpoint a specific area to keep an eye on that would be great!

Our bike also has the coil bracket service bulletin, it seems they all do. Waiting on parts to arrive at the dealer before they do that free service. Part of that service is also to verify the TPS position and calibrate the power valve and mapping switch, as well as the latest ECU "update".  I was advised not to do the bracket myself because they are taking pictures and documenting that procedure in the KTM system as they do the service.  So if you buy the bracket and do it yourself, it isn't official, plus you won't get the other adjustments and updates taken care of that go along with that same service bulletin.

Thanks again for all the effort and information and please expand on the cracked piston comment if you are able to.

Thanks for the reply and the piston picture! At least that is an easy location to check with the bore scope.

I agree with you about cast versus forged pistons, and the nearly unobtainable billet machined (edit to: hardest to find) being the ultimate, but it is disappointing that the OEM cast piston isn't a safe bet in this case. In my experience with other brands, the stock cast pistons are normally very dependable and consistent, but i am finding that KTM may be lacking in terms of QC compared to some other Japanese manufacturers. Our bike was missing a kickstand shim plate and the skid plate fell off in the first 10 minutes, for example. Maybe those were dealer installed items after removing it from the crate, but nevertheless I've never seen a new bike come with missing or loose parts before.  Dealer also mentioned they had 6 units arrive with 18 inch rear wheels instead of 19 inch (sx or sxf models, presumably) right out of the crates. That seems crazy from a QC standpoint at the factory.

My overall impression is that i love the potential of the bike, but there are some red flags that make me worry about longevity and also getting hours away from the truck up in the mountains.

Do you think using a hotter 9 plug can contribute to the piston failure in any way? The hotter plug was a band-aid fix for ECU and mapping issues, and it seems to help considerably, but i hope we aren't putting any potential extra strain on the piston crown when riding hard with a hotter plug. My son is only 12, so he isn't pushing it very hard, but i am a former A level rider and can still push a 125 fairly hard for maybe 2 laps before my old age and lack of conditioning catch up to me! That being said, I've played on his bike a few times and subjected it to some higher loads for short periods.

Thanks again for the picture, i will try to inspect ours this weekend and report back.

I believe our bore scope has a video output, so if i can find the time i will take a short video of the piston crown in the near future.

Agreed, it is strange to see a 10 come stock in a 125. Sort of like a KX65 having a 10, but nearly everyone uses a 9, just to name one similar example of several. 

In the brave new world of computerized 2-strokes, i was a bit concerned about straying away from any stock settings or specs, but the 9 plug certainly passes the real world seat of the pants test.  They also run decent on a normal BR9ES, given no other option if you are stranded. The longer standard 9ES plug can be installed with the stock XC tank in place on the 125. It works well enough to get you back to the truck, or simply to verify that the spark plug is indeed the reason the bike won't start.

I hear ya on the simpler bore scope to phone option. I just already had this one for inspecting cnc machinery in my machine shop.  It might connect to a phone, i hadn't thought of that, thanks for the tip!

Yes, can definitely see liquid gas pooling on the backside of the butterfly and the floor of the throttle body.  That definitely won't be good for consistent clean response and running of a 125.

Could this be adjusted better with the mapping? Only low rpms it happens? 

Wide open throttle then full closed do it? Or just 1/4 turn blips? Steady 1/4 held? Could maybe map lesser fuel % to correspond with the tps at the lower rpms. Can the stock ecu do this? 

 Thank You !!

Does the 2 stroke have the same map switch as the 4 strokes?

I am doing a map switch delete and I saw that the 2024 xcw doesn't have a map switch but does come with a dummy 4 pin connector? Anyone now any details?

https://youtu.be/36gR9bHGTVE

Yes the switch is different because the two strokes don’t have tc or quick shift. The 24 xcw can use the 2 stroke map switch. It is included on the Husky version of the enduro bikes. 

This is the map quick shifter TC switch from 2023 450

Great info👍

Hello, Does anyone have a summary of the problems the 2023 sx250 has? I see some people installing the injectors and mapping from the 2024. Is this necessary? and is this an expensive upgrade? I think everyone was very skeptical, but the problems turned out not to be too bad?