125/150/250/300 KTM/HUS/GG jetting thread

#434 wrote:

How do I do that? If I‘m going to do the slide mod I want to do it right so I would need a drawing or...

How do I do that? If I‘m going to do the slide mod I want to do it right so I would need a drawing or something similar. German engineer, can‘t help it...

#434 wrote:

Thanks. Yeah, that's the standard Needle/Needle Jet combo of the 2018 150sx. However, the 125 and the 150 have quite different jetting. The 150 is quite...

Thanks.

Yeah, that's the standard Needle/Needle Jet combo of the 2018 150sx. However, the 125 and the 150 have quite different jetting. The 150 is quite a bit leaner all around.

digger wrote:

In reality though, the jetting specs for the 125's and 150's are not that different. The jetting specs that have been listed above, S-4 needle jet...

In reality though, the jetting specs for the 125's and 150's are not that different. The jetting specs that have been listed above, S-4 needle jet, 42-74, i'de start out in the 2nd clip position, a 490 main along with #5 slide, are all going to be very good starting points for either a 125 or 150. The biggest difference between the 2 engines is the pilot jet, and that's only slightly and it varies as to how large, or no notch you have on the front side of the slide. Opening up the front side of the slide makes the pilot circuit more efficient, which in turn will will cause it to run richer, so you will need to compensate for this by using a smaller/leaner pilot jet.

Dexter wrote:

I finally did all the mods on my TC 250 2018, Im an average C rider I think and not very sensible to carb tunning, I...

I finally did all the mods on my TC 250 2018, Im an average C rider I think and not very sensible to carb tunning, I didn't have any problem with the TMX from factory except the massive pipe bang on deceleration.

First I did the "Jarvis" mod, truly no difference.
Then I filed the slide to a 5.25 roughly, transition low to mid was better but not night and day better
And at last the S4, 42-75 with 35 pilot and 470 main (my order was messed up, I didnt get the 480), pipe bang is well reduced but still there a little I need to try a 32.5 pilot, and above all the high range and overrev are far better and dont seem to hit a wall like before

Thanks for all the tips

Edit: straight 98 pump gas (93 US) and 55:1 fuel mix

jsippola wrote:

Just picked up a 18 TC 125. I plan on running T2 in it. What are the jetting specs you all would recommend? Thank you.

nornevrder wrote:

Hello all!!! Holy shit from reading this thread there has been a lot of work going into this. Thank you much!!!! Digger helped me get my...

Hello all!!! Holy shit from reading this thread there has been a lot of work going into this. Thank you much!!!!
Digger helped me get my 13 250 dialed back in the day when I lived in Alaska. Yesterday I picked up a 2020 and will start break in at the end of the week. I used to race the A class and Vet expert but am now 41 and am a bit washed up. I’m now back in Reno 4500’ and will mostly be doing trail riding in the hills. According to the manual stock jetting at 60:1 will work until it gets warmer. I have also read some good things about the JD kit and their support. Are these mods a must do for the type of riding that I will be doing? Is the stock jetting really that bad?

Dannyderasmo106 wrote:

Anyone running 93 pump 50:1 in a 19 250? Looking for some settings to try.

yellow97tt6spd wrote:

Thanks AJ and Digger for all the work you guys have done on fixing up the jetting. First post to the group, but I’ve read through...

Thanks AJ and Digger for all the work you guys have done on fixing up the jetting.

First post to the group, but I’ve read through several posts these last few months, as I was looking for a 2018 250 SX. Picked one up, and changed out several things, but noticed I did one thing incorrect... When I ground my factory slide I added 1mm around the entire radius (not just the very top). Put it together and rode with it (about 30 minutes), and the bike was way better down low, but in reading through another thread I noticed I shouldn’t have widened the opening. Also, I only modified the air filter side of the slide (as that was the side that I’d seen discussed more in depth) and figured since the two slide mods should make it leaner, if I didn’t touch the smaller reeds side notch, it would only leave it slightly richer overall than a “total modification”.

So far I’ve completed the Jarvis Mods, float adjusted, s-4 needle jet, 35 pilot jet (1.75 turns), 470 main (to start... 100* out), and plan to order the leaner 42-75 needle (still 43-73 and clip at #3). I’m running 2/3 93 with 1/3 c12, at 50:1.

The BIG question... Did I trash my slide? Bike seems great down low (0-1/3), and just feels a bit more sluggish now up top, but I haven’t got the leaner needle yet, and I started out running a very large main (at ~600’ and 100*). Between the needle and the main size, and the heat, I think I can clean up the top, but I’m worried about overall efficiencies. Will this grenade my motor? Lol. How much power might be losing from the wider slide notch?.. Should I order a new one?

And FYI... The other mods to the bike are a Pro Circuit pipe, and 296 Silencer (neighbors). Figured I should be jumping one main jet size for the pipe alone, and when I first picked it up a month ago, it pulled really solid with the 440 main it had. I was never a jetting Waze, and just wanted to start with a set up it was very conservative. Between my minimal slide modification, the larger pilot jet (without the leaner needle), and the three steps up in the main jet, I think there should certainly be better response available. Just seemed you were always talking about huge main jets (even when not running oxygenated fuel), and wanted to start conservative.

I just need to make sure I get this right so my four year old doesn’t start out running me on his PW50.
:-P

Thanks again, and please advise!