So I picked up a new 23’ KTM 125 last night and since this engine and the EFI system is all new for 23’, I’m going to be doing a breakdown of the engine and what’s going on inside of it.
Some of the points I am going to go over are the TPS circuit, the EFI circuit, the PV, and basically explore the tech inside.
Some of these talking points will translate directly over to the 250/300sx as well since it shares the same tech.
This is going to be a fun project for this winter, a video series would probably be best as that’s the way things are done now.
I’m going to start with going over the bike and pointing out some features and also start with a brand new engine, compression check bone stock, and most likely a dyno run to document what this motor makes out of the crate. Do some mods and then do some more dyno runs.
I don't think there will be many tuners willing to share secrets and post them, or advances in engine solutions, so I love to do this as part of passion for 2 stroke engines.
Stay tuned and let the bashing begin lol.
https://www.youtube.com/@godguitarsgunsandgoats691/videos
https://www.facebook.com/groups/709915283880183
The stock dyno runs will be a good sign of what is there and we will be able to compare the before and after mods of that.
The first part of this will just be more of a familiarizing the new tech and discovering any issues and documenting the findings.
I want to check squish clearance, initial TPS voltage, compression, analyze the PV, etc.
Some may find it useful, boring, or both..lol I just wanna do it bc I’m super into this stuff and am a geek about how and why things work.
The engine tuner in me wants to tear into the motor and port it, cut the head, etc but as far as I can tell that would be a very bad idea bc of the EFI.
This is bc the parameters of the ECU tune are considered like a closed system where the ECU doesnt have the ability to correct for changes that have been made to effect the volumetric efficiency of the motor..it doesn’t get “feedback” from the changes on the fly it can only really monitor air temp and AF ratio.
For ex) if I cut the head down to increase the compression the ECU won’t know that and just continue to feed the engine what it would normally push thinking it’s the same when it is not.
Anytime you port a motor, or head work, you have changed the tune of the motor and adjustment is needed, bigger or smaller jets, or in the 4 stroke world, an aftermarket ECU tune is common as there are small fuel trim dials to send or restrict fuel in the low-mid-high rpm range.
This ECU does not have any flex tuning available so head mods, porting, etc may make the engine run lean and hot real quick after the mods.
Kinda wordy but hopefully I made a point to it.
More soon-
Looking forward to this. Much thanks for your efforts.
The Shop
Goodstuff not keeping it all secret squirrel.
Kinda like when you run a shorty, the typical longer silencers have more upper rpm pull so I will measure up the stock set up and the FMF I have coming.
Definitely the case on the 450, the fmf on the Rockstar sticks out an inch further than stock
2023 KTM 125sx deep dive 125 overview
Pit Row
2023 KTM 125sx TPS video
I have a pipeset and reeds coming and from what FMF and VForce really wake up the mid-top. We will see!
On a side note, I’d be curious to see how the chain slack is when shipped from the factory. The lower swingarm pivot on the ‘23’s requires more slack and I’ve seen a few new KTM’s shipped with the chain too tight. Might be cool to remove the shock and see what the optimal chain slack is. I was looking at the manual for the 300’s and it still listed the older chain slack value (pre ‘23) but I believe there’s a sticker in the airbox showing the updated measurement.
The wake up connector is just that it plugs into a dongle and will reset the parameters of the pv open/closed..mine was laying in the bag they gave me.
more soon! Thx
Seems a market to pursue, but, maybe they've enough on with 4ts?
They'll be leaving it to GET, and all the others to make money. FI 2ts are not going away.
Sure they may be more difficult a thing to do ( I've no idea if there are more sensors etc on the 2ts, but, of course you've the faster / more often / shorter fueling 'times') , but, I can't see why you'd not do something that enables tuning. The 4t systems on Dirt Bikes aren't particularly 'intelligent', either.
Other vendors will pick up the slack, I'm sure of it. It wasn't instantaneous when 4ts went EFI, either.
Options for the rear brake!
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