ISO 2020 KTM 250 SX Tips

Teej317
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Teej317
Picking up a new old stock '20 this weekend and looking for tips on dialing this bike in....

Carb....I've done my research on the Mikuni situation and opinions are high and wide on that topic. I look forward to messing with it based on what I've learned and seeing if I can't dial it in (i'm at around 3500 ft here in Montana). I'm open to suggestions here.

Fuel.....I've always had great success with Motul 800. 60:1 seems crazy but that's what the manual says. It also calls for "95 super unleaded". Highest octane around here is 91...am I okay to boost it a little with 110 race fuel?

I appreciate the info!
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opyguy
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opyguy 3/2/2021 3:53pm
3/2/2021 3:53pm
Had a 17
Used motorex synthetic 60:1
100 hours 0 issues, piston done at 50 and was perfect
Just got a 21, stock jetting seems fine, much better than the 17
Bike could use a bit more over rev, but light as shit and handles great...point and shoot
2
Teej317
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Teej317 3/2/2021 3:59pm
3/2/2021 3:59pm
opyguy wrote:
Had a 17 Used motorex synthetic 60:1 100 hours 0 issues, piston done at 50 and was perfect Just got a 21, stock jetting seems fine...
Had a 17
Used motorex synthetic 60:1
100 hours 0 issues, piston done at 50 and was perfect
Just got a 21, stock jetting seems fine, much better than the 17
Bike could use a bit more over rev, but light as shit and handles great...point and shoot
Thanks for that report 👍
Brent_KS
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Brent_KS 3/2/2021 6:20pm
3/2/2021 6:20pm
18 TC250 been mixing 60:1 as well and zero issues at 105hrs and pistons always look good when changed. My highest fuel is also 91 and no issues at all just get your jetting dialed in and you will love the bike!
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JohnMatrix
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JohnMatrix 3/2/2021 9:48pm
3/2/2021 9:48pm
Awesome bikes. I took my 19 out this past weekend after not having ridden it for a few months. The 19+ shock is really good. You might need to go up 1-2 spring rates depending on your weight. Once you dial in the mikuni it runs much better and throttle response is great. The long pro circuit silencer does add some noticeable over rev in my opinion. Basic ktm things I always change...the bars are too low and flat for me at 6’. I always put a Fasst co rear brake spring conversion on. I also always put a cheap eBay extended brake tip on my ktm’s. Enjoy the bike, they’re fantastic.
sandman768
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sandman768 3/3/2021 6:04am
3/3/2021 6:04am
Curious to see what the stock jetting is? Close to what we have been doing to our 17-19”s ?
opyguy
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opyguy 3/3/2021 6:07am
3/3/2021 6:07am Edited Date/Time 3/3/2021 6:10am
35 pilot 450 Main 4371 needle and the S1 needle jet
I had a 17 that I struggled with. I used AJ’s jetting as well as trying that 1762 Suzuki needle. I’ve only got eight hours on my 21 but I’m telling you the thing runs crisp and mint
1
timobijnen84 3/3/2021 7:11am
3/3/2021 7:11am
The 95 octane fuel is european spec RON95. RON95 is around 85MON so there is no problem with running 91.
1
YZed250
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YZed250 3/3/2021 11:56am
3/3/2021 11:56am Edited Date/Time 3/3/2021 2:36pm
The only thing I'd like is a little bit more top-end and hook-up (hard pack) compared to the four-strokes, IMHO.
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JK714
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JK714 3/3/2021 1:30pm
3/3/2021 1:30pm
If you've got the carb off the bike and apart, go ahead and check the jetting block gasket. They're very thin rubber, and if/when they fail the bike will run terribly no matter what you do. It's under a little oval plate inside the bore, with two torx screws.JD Jetting makes a metal replacement that solves the issue. Plenty of videos out there on this.
JohnMatrix
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JohnMatrix 3/3/2021 1:53pm
3/3/2021 1:53pm
opyguy wrote:
35 pilot 450 Main 4371 needle and the S1 needle jet I had a 17 that I struggled with. I used AJ’s jetting as well as...
35 pilot 450 Main 4371 needle and the S1 needle jet
I had a 17 that I struggled with. I used AJ’s jetting as well as trying that 1762 Suzuki needle. I’ve only got eight hours on my 21 but I’m telling you the thing runs crisp and mint
Yes this, I switched over to the suzuki needle that you recommended and it's working great with the 5.75 slide. I had tried the S4 needle jet and supporting changes first and they were also great. Decided to try the S1 with the 1762 needle and supporting changes for the heck of it. I haven't found any real seat of the pants difference between the two settings, which is good, meaning that there are several ways to skin this cat.

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