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Base gasket replaced
32.5 pj
As1.5
Jd blue needle on clip pos 5.5
Mj 460
Slide 4
Nj R8
99 octane fuel 60:1
This seems to work well but I am going to try the settings digger and aj have recommended, I am in the uk with temps around 15c at sea level full hgs. What are people setting their float height to? And are the settings recommended by aj and digger still a good starting point for me? Thanks again to everyone on this thread 👍
The Shop
I feel my bike runs a lot better that stock, but I’m not very good at these things, so maybe you can help me? As I said I’d like to test AJ’s setups,if you believe those runs well also in here?
I hope you understand my bad english. Thank you guys!
I will make it a little richer than your setup and see if it feels too rich. I think it’s colder and more oxygen rich in here, so believe it is better to start with rich setup.
I’ve been thinking to chance my pipe for PC, but it is a little bit difficult to buy in here.
I managed to ding my stock pipe so I am now running the FMF Fatty Series with FMF Turbincore 2 silencer... my jetting is exactly as AJ's from the front page (main, pilot, slide, etc.) The FMF Fatty smoothed out the bottom end but still kept that awesome pull up and through the top end. I balanced it by running the vented cover (I was given both) to lean it out a touch and it gave that bottom end kick back
This is on the 2021 KTM 250sx.. runs beautifully on the motocross tracks up here in PNW in temps 45-80F so far at 0-1,000ft tested.
I've been planning to add 300cc kit and change the pipe for FMF or PC, but before that, I'd want to make that 250 HGS setup run as good as possible. I'm mostly riding MX, but I also ride in forests and some more difficult areas, so I'm mostly looking for stronger bottom end and easier handling. More top end and over-rev are also welcome, but the most important thing is to improve tight corners and other slow speed areas.
Interesting thing to note that I learned with fuel testing, 10% ethanol pump would cause a rattle noise at higher RPM with a very light load on it. I’m not sure it it was a knock or a piston flutter hitting the cylinder walls, but I went back to ethanol free and it went away. I had my buddy try the same fuel and he also noted the same noise in his bike. That could be the pipe bang that some people talk about.
Pit Row
Mikuni TMX 38
5.0 Slide
S4 needle jet
42-74 needle
clip 2
30 pilot
2-2.5 AS
470 Main
1.75 turns PV adjuster (from fully CCW) (Yellow spring)
91 pump ethanol free
either Motul 710 or Klotz TCW3 (Kl-302) @40:1
Temps are looking to be between 60-90F @4,500 or so
Once you get the mikuni dialed, it's a tremendously good ride and experience, just amazing clean and crisp running.
The STIC is either different or an improvement depending on how you look at things... certainly a much different riding experience.
As for porting and head mods, definitely ride the bike for a baseline. Quite often, it just moves the power vs increasing jt... this is where the dyno is key, so hopefully you can find a tuner with a validated setup.
I agree with you on building the bike is part of the fun, but so many times it's taken away some of the fun as well messing around with stuff that doesn't fit or work as perfectly as advertised. So insane these bikes stock blow away any of the Japanese 125s
Moving around the power might be a good thing - instead of a big midrange hit and then falling off, a smoother, wider, more linear powerband might be just the ticket I'm looking for. Like you say, gonna ride it as is, with just the stock carb mods first and go from there. It is fun to experiment though
Post a reply to: 125/150/250/300 KTM/HUS/GG jetting thread