2019 KTM 250SX Must do's?

I have a 18’ but I would definitely say the jd jet kit, race gas, and red spring will make you happy with the motor. I’ve never had a 2stroke that felt so linear the powervalve transitions seamlessly (especially after getting the jetting dialed)
As a fast rider you most likely won’t like how short 3rd is so a 49t sprocket is what a lot of guys switch to.

lukemoto wrote:

I have a 18’ but I would definitely say the jd jet kit, race gas, and red spring will make you happy with the motor. I’ve never had a 2stroke that felt so linear the powervalve transitions seamlessly (especially after getting the jetting dialed)
As a fast rider you most likely won’t like how short 3rd is so a 49t sprocket is what a lot of guys switch to.

THANKu for the response, was gonna order 4-5 rear sprockets. and test them

get the head sorted(squish), JD jet block gasket, either the Jarvis mods or JD kit, 49t rear sprocket and that is about it to get started. Can go further naturally, but this bike is really good off the showroom floor.

Check the reeds if you arent going aftermarket. Its not uncommon to have bad ones off the showroom.

Not getting the 450 fe?

mxb2 wrote:

Not getting the 450 fe?

i want to still but need to buy my son a 65 and no reason in me being selfish.

mxb2 wrote:

Not getting the 450 fe?

4csHATER wrote:

i want to still but need to buy my son a 65 and no reason in me being selfish.

Ok

The jetting we’ve figured out for the ‘17-‘18 also works well on the ‘19 since it come rich too. Needs a pipe and silencer for more over rev and drop a tooth in the rear. I also run straight u4.4 as it was a noticeable power increase over C12.

Chassis wise a rear link and a steering damper help a great deal. The forks still benefit from a revalve.

It doesn't need much. If you want to mess with it, by all means. What it needs and what you want are different! The beauty of this bike is that you can run it stock, no need to mess with anything.

A normal race prep (Loctite, tubes, grease, your favorite bars, oil the filter, set the air screw) is all it really needs.
After that, find your favorite gearing, pv setting, add an ERT2 and start burning premix.

If you want to make sure you are jetting from a good and stable staring point, I would replace the jet block oring and gasket. The stock jetting worked awesome on my 2017 with the small change to the needle clip position. So I never found the need to replace the jet block oring and gasket, but I have them sitting there in case it starts to run bad.

Now that I have done all of the basic race prep, I am looking for some better feel/comfort from my AER fork for 1.5-2hr races, but for moto, you might just run it as it is.

Thanks guys for all the responses. I winded up purchasing a 2018 250sx, i know its the older model and all that jazz but it allowed me to put mods on it sooner, and have more money to work with for my sons 65/50 and 55gal of vp!

so after purchasing yesterday, i immediately headed to rocky mountain atvmc and on scratch and dent they had a pro circuit plaitnum pipe for 90$ that had a minor dent nothing serious, so i went ahead and picked up a silencer and jd jet kit and set of plastics and a seat cover and a set of bars, a air box wash cap, renthal 49t sprocket and a stand.


Im back, back in the saddle again. im back.

I highly recommend doing the jetting AJ565 posts about in his bike build thread. It helped clean up the mid throttle. I also agree with a pipe and silencer and drop to a 49 tooth.

4csHATER wrote:

Thanks guys for all the responses. I winded up purchasing a 2018 250sx, i know its the older model and all that jazz but it allowed me to put mods on it sooner, and have more money to work with for my sons 65/50 and 55gal of vp!

so after purchasing yesterday, i immediately headed to rocky mountain atvmc and on scratch and dent they had a pro circuit plaitnum pipe for 90$ that had a minor dent nothing serious, so i went ahead and picked up a silencer and jd jet kit and set of plastics and a seat cover and a set of bars, a air box wash cap, renthal 49t sprocket and a stand.


Im back, back in the saddle again. im back.

Congrats! I believe it was in MXAs test on the 19 that they said they preferred the feel of the 18’
One thing I don’t think I saw anyone mention is the stock bar mounts. Even the smallest tip over will leave the front end out whack.

lukemoto wrote:

Congrats! I believe it was in MXAs test on the 19 that they said they preferred the feel of the 18’
One thing I don’t think I saw anyone mention is the stock bar mounts. Even the smallest tip over will leave the front end out whack.

thanks im thinking about makig the switch to neken clamps or luxon clamps, and conevalve forks and or kyb sss that gets kashima and internal mods.

4csHATER wrote:

thanks im thinking about makig the switch to neken clamps or luxon clamps, and conevalve forks and or kyb sss that gets kashima and internal mods.

I have CV and Neken spring/air clamps and its an amazing set up. The clamps need to be run over 100 psi or you bottom them out like crazy.

4csHATER wrote:

thanks im thinking about makig the switch to neken clamps or luxon clamps, and conevalve forks and or kyb sss that gets kashima and internal mods.

Use promo code VITAL-2019 at checkout for 15% off if you end up going with ours!

Luxon MX wrote:

Use promo code VITAL-2019 at checkout for 15% off if you end up going with ours!

Thank you.!

AJ565 wrote:

I have CV and Neken spring/air clamps and its an amazing set up. The clamps need to be run over 100 psi or you bottom them out like crazy.

Thanks for the responses, should i be concerned about breaking the bike in on t2 or u4.4? its been a long time since i have ridden a two stroke and last time i did i was using 40:1 in a rm85 so why does the manual call for 60:1 like my sons ktm 50?

what premix and jetting specs are you guys using, i ordered the jd jet kit, and it seems to be here in a day or two should i wait to break the bike in witth the jet kit installed? should i have broken it in with all stock parts and pump gas? im just lost now.

It has a pro circuit plaitnum pipe and factory r304 on it.

it has lump fuel in the tank but am willing to dump it out since when i walked to the back of the dealership they had a ragged out gas can that wasnt capped off dumping gas into the tank, the shop was bery dirty and alot pf dust was in the air so i told the mechanic that was doing the pdi to not start the bike, as i knew it had no air filter oil on the filter.

That shop was beautiful in the front but ragged out in the back from muddy atv's and utv's i cant beleive they were doing service work in there witht all the dirt and grime flying around in the air.

im thankful i caught the mech before startingn the bike, im pulling the tank later today and dumping the fuel and will mix my own fresh batch if pump fuel is what i should run through it.

i also thought about running vp T4 mixed with castor 927 through it to break it in.


please give me some feedback as i have been on the four jokers for years.

I wouldn't worry about breaking it in on that, BUT you have to change jetting for that fuel or you will be way lean.

This is my current jetting for u4.4 mixed 44:1 and amsoil dominator
MJ 490
PJ 35.5
Needle 42-75 (KTM option part)
Slide 5.75 (2004 KX125 option part. Stock is 4.0)
Clip 4th position or 3rd depending on temp.
Needle jet s-4 (stock is a s-1)
AS 1.5
PV 1 3/4 turns in stock spring

Here is a link to my build. I've done a lot of the hard work on getting this bike dialed in carb and chassis wise. Next up is engine mods. Build thread

Millennium tech ported and polished my head and cylinder on my 17 and it made it a monster. Also had JD Jet kit. I ran renegade pro 110+ 50/50 with motul 800 at 40:1 without a hiccup. I think I touched the airscrew twice.

Easily one of the cleanest most predictable running motors. Watch the motor mount bolts they like to come loose, so do the subframe upper bolts.

Highly suggest sending your suspension to factory connection. They know how to do AER very well.

Also, i feel like nobody is doing KTM decals as hot as I am. Hahaha. Check my insta @rippinruts

Millennium tech ported and polished my head and cylinder on my 17 and it made it a monster. Also had JD Jet kit. I ran renegade pro 110+ 50/50 with motul 800 at 40:1 without a hiccup. I think I touched the airscrew twice.

Easily one of the cleanest most predictable running motors. Watch the motor mount bolts they like to come loose, so do the subframe upper bolts.

Highly suggest sending your suspension to factory connection. They know how to do AER very well.

Also, i feel like nobody is doing KTM decals as hot as I am. Hahaha. Check my insta @rippinruts

Rode the bike today for the first time and upon break in, 1.2 hrs runtime, i was hitting a roller section and it bogged hard and acted like it was over heating hard core set there for a minute and treated the bike as if i was letting it cool down and everytime i would rev it a little in a five minute cool down spirt it would bog hard, went back to truck and shut it off, let it cool down and went back out and rode it not hard for about 20 min and it never did it again. I am super nervous now about this bike and think i may have gotten a lemon. im gonna take it back to dealer maybe tomarrow.Pretty bummed. 1.2 hrs and it had a fuel delivery issue already.

4csHATER wrote:

Rode the bike today for the first time and upon break in, 1.2 hrs runtime, i was hitting a roller section and it bogged hard and acted like it was over heating hard core set there for a minute and treated the bike as if i was letting it cool down and everytime i would rev it a little in a five minute cool down spirt it would bog hard, went back to truck and shut it off, let it cool down and went back out and rode it not hard for about 20 min and it never did it again. I am super nervous now about this bike and think i may have gotten a lemon. im gonna take it back to dealer maybe tomarrow.Pretty bummed. 1.2 hrs and it had a fuel delivery issue already.

4csHATER wrote:

Rode the bike today for the first time and upon break in, 1.2 hrs runtime, i was hitting a roller section and it bogged hard and acted like it was over heating hard core set there for a minute and treated the bike as if i was letting it cool down and everytime i would rev it a little in a five minute cool down spirt it would bog hard, went back to truck and shut it off, let it cool down and went back out and rode it not hard for about 20 min and it never did it again. I am super nervous now about this bike and think i may have gotten a lemon. im gonna take it back to dealer maybe tomarrow.Pretty bummed. 1.2 hrs and it had a fuel delivery issue already.

The PJ is what caused it if its too rich. I had my bike do that and a 150sx do that. I dropped both bikes one PJ size and problem solved. You also need to make sure the float is adjusted correctly.

will a lectron take all of this headache away?

AJ565 wrote:

The PJ is what caused it if its too rich. I had my bike do that and a 150sx do that. I dropped both bikes one PJ size and problem solved. You also need to make sure the float is adjusted correctly.

is there any way you can email me? austinrankin618@gmail.com

Lectron won't be the unicorn feather you want it to be. Spend a bit of time doing the Jarvis mods, that is free. I would personally do this and the JD jet block gasket and float seat oring update before spending $350+ on a new carb, no matter the brand. I have had them all and like my Smart Carb, but many will argue for the Keihin or Lectron too.

You got the JD kit. Call JD. He will set you straight 100%.

You got an 18 right? Which probably means its been sitting at the dealer for over a year. If there was any gas in the tank / float bowl during that time its probably gone to shit and may have clogged some things up. Make sure theres no crap in the float and all the jets are clear.