ESE's works engine tuner

[Frits Overmars]

All way complicated and not necessary, the Dellorto had a 10mm long main jet extension that screwed into the emulsion tube end, and an extended float bowl bowl nut.

Something like this? And with ultra-open foam (the red stuff) to prevent frothing?

[TZ350]

All way complicated and not necessary.

Yes, in the end, the complication may kill the twin fuel idea. But the idea intrigues me. So I would like to prepare a second carb as a comparison. I have some time as I am unable to use the dyno for a while. There is a freshly painted classic Ford pickup parked behind the dyno getting its final touches and no ways am I going to risk blowing a paint pealing mixture of two stroke exhaust over it.

[katinas]

Some pictures of the latest KTM SX 125 EFI engine.
Crank plastic inserts screws must be checked and "re loctited" as they have a tendency to loosen after few rides.

[Tim Ey]

Some pictures of the latest KTM SX 125 EFI engine.
Crank plastic inserts screws must be checked and "re loctited" as they have a tendency to loosen after few rides.

Really interesting hamster cheeks in the crankcase. If I recall correctly, the 2017 SX did not have that. Whats the reason?
- pre compression ratio increase?
- better flow out of reed?
- extention of the back B-Port wall?
- all of the above?

Regards
Tim

[husaberg]

Really interesting hamster cheeks in the crankcase. If I recall correctly, the 2017 SX did not have that. Whats the reason?
- pre compression ratio increase?
- better flow out of reed?
- extention of the back B-Port wall?
- all of the above?

Regards
Tim

They likely could also not get enough material off from the inside whilst supporting the pin.
thats seems to be a large wall thicknes on the pin.
#The early at least 85's tend to melt the inside stuffers.

edit sorry i thought you meant the crank not the cases

[TZ350]

.


Making good progress on the Meth-Petrol-Carb. Sealing ring in the float bowl nut. Petrol in the carb and methanol in the remote float chamber.

Petrol for the primary fuel circuit and methanol for the needle and main jet.

The remote float chamber has 5,5mm galleries and a 4,2mm float valve.

Next move is to add an adjustable methanol power jet and fuel level indicator like the one on the straight methanol carb.



Straight methanol carb with Wobblys Dellorto 4,2mm float valve and adjustable power jet. The fuel level can be seen in the clear tube.

[F5 Dave]

Oh yeah. Forgot it is Rotary so side of engine.

[TZ350]

.


The completed petrol/methanol carburetor with adjustable power jet.

[koenich]

Really interesting hamster cheeks in the crankcase. If I recall correctly, the 2017 SX did not have that. Whats the reason?
- pre compression ratio increase?
- better flow out of reed?
- extention of the back B-Port wall?
- all of the above?

Regards
Tim

this was done so some "tuner" can regrind the cases, cut the head, recommend to use 190 octane fuel and make a story how it now revs to the moon.

kidding aside, I'm sure KTM had a reason to do so - would be interesting to know it, all your reasons make sense.

[katinas]

Really interesting hamster cheeks in the crankcase. If I recall correctly, the 2017 SX did not have that. Whats the reason?
- pre compression ratio increase?
- better flow out of reed?
- extention of the back B-Port wall?
- all of the above?

Regards
Tim

Yes, looks like these crankcase "glands" match the flow from V force type reed block very well. But the last carb engine tuned version, still have 4-5 hp more and it is very noticeable on the track.
Without easy possibility to change fuel rate on EFI engine, tuning is complicated.

[F5 Dave]

Ready to Race.

With an arm tied behind your back.

[TZ350]

But the last carb engine tuned version, still have 4-5 hp more and it is very noticeable on the track. Without easy possibility to change fuel rate on EFI engine, tuning is complicated.

That is interesting, KTM carburetor engine makes significantly more power than the EFI version. My experience with two stroke EFI is that you can easily match or better a carb engine for maximum power and over rev. With access to the fueling maps EFI is so easy.

[Grumph]

That is interesting, KTM carburetor engine makes significantly more power than the EFI version. My experience with two stroke EFI is that you can easily match or better a carb engine for maximum power and over rev. With access to the fueling maps EFI is so easy.

Neutered by having to meet Euro emissions regs ?

[TZ350]

.

I am not sure why 2S EFI should find it harder to meet Euro standards than a carb engine.

Flettner who has way more real world practical riding experience with 2S EFI than me. Reports that with transfer port injection (TPI) there is a noticeable fuel saving which would suggest there is less fuel wasted through charge short circuiting. That has to mean a cleaner engine exhaust.

KTM copied Flettners TPI idea then went to reed port injection. Injecting before the reed valves looks like a poor mans carburetor to me. With all the problems of a crankcase full of fuel mixture, some of which is lost through short circuiting.

Again from my 2S EFI experience. A 125 is much harder to map properly than a 300. I suspect, maybe KTM has found mapping a 125 for the vastly more dynamic on pipe/off pipe conditions a challenge. There is a way but it is much more tricky than working with a 300.

[Peter1962]

That is interesting, KTM carburetor engine makes significantly more power than the EFI version. My experience with two stroke EFI is that you can easily match or better a carb engine for maximum power and over rev. With access to the fueling maps EFI is so easy.

On the ktmtalk forum there are a lot of stories on problems with the SX125 with failing crankshafts since model 2022. Some think that KTM did not properly solved the problem, but in stead limited the Maximum RPM on the TBI 125 SX model 2023 to avoid catastrophic failures... Poor choice. https://ktmtalk.com/threads/2023-125-sx-crank.569456/

The ktm 125 model 2022 had more HP than the model 2023.

But the 250 SX TBI 2023 has more HP than the previous model, so I do not think that it depends on the injection but rather to the choices that the ktm engineers implemented concerning the mapping.