playing with a 2017 ktmsx250

flomiester
Posts
187
Joined
2/10/2012
Location
Elwell, MI, USA


Im no longer a 2 stroke wizard or maybe i neve was i use to build pipes and port cylinders for sleds . But i got a request to work on this 2017 250sx and performed some simple changes in the porting i always have had a diferent aproach to shaping an exhaust port even on the sleds and not letting the exhaust wave just dump into the port so with some advice on the transfers and my work on the exhaust port theses were the results i also increased compression by .5 .nothing else is done to the bike yet .the magazines say the bike hits to hard from the beginning of the curve my port work may have taken care of that i really would have rather seen it stronger but thats usally what happens .next step is put the rider on but dyno will tell the story and produce the final tuning .
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Markee
Posts
3669
Joined
4/15/2013
Location
Suffolk, VA, USA
3/24/2017 12:07pm
3.5 HP not a bad jump.
Motofinne
Posts
11634
Joined
1/4/2014
Location
FI
3/24/2017 12:15pm Edited Date/Time 3/24/2017 12:17pm
Not bad, that is roughly the same HP as the 350(if i remember correctly). And higher than the weakest 450s!
3/24/2017 1:02pm
Motofinne wrote:
Not bad, that is roughly the same HP as the 350(if i remember correctly). And higher than the weakest 450s!
considerably less than any modern 450 on rons dyno with exception of maybe rmz on a bad day.

Good work ron Wink
FI2T
Posts
700
Joined
10/23/2012
Location
Kennewick, WA, USA
3/24/2017 2:15pm
Nice! The curve looks great! Are you leaving it be or searching for more?

The Shop

flomiester
Posts
187
Joined
2/10/2012
Location
Elwell, MI, USA
3/24/2017 2:23pm
Im going to install the v force reeds to see what they do to the power and curve i quess the stock reeds have a tendancy to break im also going to test a different silencer a shorter fmf just to see what it also does .As Derek sugested we may get a 38 carb from a yamaha and test it . a lot of this may not even show up on the dyno .@ some point i would like to try some dispacement but i think i will do it with a little bit of stroke like 2 mm .that should help the bottom hit come back and it willincreae the port durations slightly helping the top some more did this years ago on some 2 strokes with good track results .

seth505
Posts
10218
Joined
4/1/2008
Location
SD, CA, USA
3/24/2017 2:49pm
Very cool. I don't even need more power from mine (I weigh 155 lbs) but it's fun to tinker. I just put on the vforce 4R reed cage and got HGS/Buds exhaust. The exhaust combo dropped just under 3 pounds from the stock system.
Joe Schmoe
Posts
36
Joined
3/23/2017
Location
Lutz, FL, USA
3/24/2017 4:17pm
I have a 55+ hp chart of that bike with a Varner carb, (39.5mm bowl blended PWK quad vent) DEP pipe, and Bud silencer. Laid on top of that radical 3 speed CR that Varner also did, the curves are identical except the entire KTM curve is pushed a few thousand Rs to the right. These bikes have serious potential.

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