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2019 300xc to 300sxs?

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Does anyone have experience using a 300sxs cyldiner/head/cdi on a 300xc? I have 60hrs on a 2019 ktm 300xc and overall I am unimpressed with the motor characteristics. Moderate low end torque -> a quick punch of midrange -> falls flat on its face all while feeling a bit rough. Not like a crisp 2stroke I am used to riding over the years.  I added Lectron carb and oem mod head from Slavens and didn't find the upgrades to be worthy of the monetary investment. 

I am thinking of going to a PWK 38 and the SXS kit to bring back some pep and aggression to the motor. I really want to make this bike right as I do enjoy many of the other attributes. I ride AA / 30a at NEPG TSCEC and local offroad events. 

Feedback would be appreciated. 

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The lectron smoothed the motor so went the wrong way to what you wanted

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2 hours ago, ctb108 said:

i am thinking of going to a PWK 38 and the SXS kit to bring back some pep and aggression to the motor. I really want to make this bike right as I do enjoy many of the other attributes. I ride AA / 30a at NEPG TSCEC and local offroad events. 

Feedback would be appreciated. 

Current setup ('17 300 XC)

  • Reeds:  Boyesen RC2 Rad valve
  • Head: 300 SX, shaved 0.5mm
  • Exhaust:  PC
  • Silencer:  PC Shorty
  • Carb:  PWK 38 AG
  • Red PV spring
  • Fuel:  VP / Sunoco 110
  • Oil:  Yamalube 2R @ 40:1

I was unimpressed stock, but the shaved 300 SX head really woke this thing up.  It runs like a scalded ape now.

Haven't tried the SX ignition yet but I've read good reports here on it.

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My current setup (2017 XC 300)

-Head: RK-Tek

-Reeds: VForce4

-Pipe: Pro-Circuit

-Silencer: FMF Turbine Core

-Carb: Lectron

-PV setting: Yellow Spring one turn in from flush

-Fuel: 91 Ethanol Free

Oil: Amsoil Saber 80:1

CDI: SX 300 (SXS14300390)

 

My bike rips. Especially after I put the SX 300 CDI. It made it an animal with a monster mid range hit. I dialed the pv spring out to smooth out the hit.

Now it has gobs of power and torque off idle and just keeps on pulling. I hardly ever fan the clutch to get it to rip. Just twist the throttle more. I even like to run it a gear high and it just pulls like crazy.

I ride in deep soft sand the majority of the time and really appreciate the power.

I would first try getting the SX 300 CDI for trying anything else.

We have two bikes setup the exact same way and they both rip.

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Also one of the two bikes started out with a Slavens modded head as well, but ended up switching it to a RK-Tek.
Both heads produced good power, but the RK-Tek head was a bit cleaner right off the bottom making jetting easier to produce that crisp clean response.

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Hey everyone thanks for the feedback, this is very helpful. 

Farmboybunk do you have the specs on your lectron? Which slide are you using? MM out on the metering rod? I am definitely after that crisp response. 

Sounds like I either need a sxs / rk head and the 300sx cdi. Ill see if I can get my hands on these and report back. 

Thanks again. 

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Already given lots of good advice. I have the same bike. My 2 cents:

1st - Different CDI. 2016 and older 300 SX CDI can and has been run on 2017 and up bikes. Hotter than 2017 and up SX CDI. You can use 250 SX CDI also. Russell Bobbit ran a 250SX CDI on his 2019 300 when he got top 3 at a national Enduro early this year. 

2nd - Sell the Lectron. Buy a Keihin 38 and a STIC metering block. I have run Mikuni, Lectron, Smart Carb, and now Keihin with STIC on my 2017 300 XC. All purchased by me and tested. STIC has best throttle response and top end of all by far. 

3rd - Misc. info. I am fan of RK Tek stock head re-shape. $150. Play with the Power Valve to get motor characteristics you like. I am running the Red spring with a Kreft PowerDial. On the fly adjustment. http://www.kreftmoto.com/powerdial/powerdial-20

Don't give up, this year 300 can be made into a monster with small changes. Most of all, don't be afraid to throw fuel at it. 

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Hey everyone thanks for the feedback, this is very helpful. 

Farmboybunk do you have the specs on your lectron? Which slide are you using? MM out on the metering rod? I am definitely after that crisp response. 

Sounds like I either need a sxs / rk head and the 300sx cdi. Ill see if I can get my hands on these and report back. 

Thanks again. 

I have the 4-2M meter rod. I know they now recommend a 5-1 for our bikes, but my bikes running so good I have no desire to switch and try it. I’ll have to check what mm I have the rod set at.

I’ve adjust as needed until I had it just right for my bike and oil ratio and never paid attention to where it’s set at.

I’m just noticing now that when I installed the SX CDI that it leaned out my bottom end.

I hadn’t noticed at first because it’s been so darn hot that I’ve been riding at elevation, but now that I’m riding at lower elevation I can tell I need to richen up the meter rod a 1/4 turn.

When I do I’ll check and see what the setting is at.

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On 9/28/2019 at 9:48 PM, farmboybunk said:

I have the 4-2M meter rod. I know they now recommend a 5-1 for our bikes, but my bikes running so good I have no desire to switch and try it. I’ll have to check what mm I have the rod set at.

I’ve adjust as needed until I had it just right for my bike and oil ratio and never paid attention to where it’s set at.

I’m just noticing now that when I installed the SX CDI that it leaned out my bottom end.

I hadn’t noticed at first because it’s been so darn hot that I’ve been riding at elevation, but now that I’m riding at lower elevation I can tell I need to richen up the meter rod a 1/4 turn.

When I do I’ll check and see what the setting is at.

All great advice so far... nothing to add besides I highly recommend Keihin 38mm pwk airstyker short body. I had the mukuni on my 19' and it was good...but had fueling issues down low and it doesn't adjust to temp elevation etc as well as the keihin can.  After some guys like redrider helped point me in the right directions this 19' is a monster. Rk Tek head is also a great investment. 

Farmboybunk:

funny you say that i was just going to ask what did you notice from stock xc cdi to sx300 cdi?

I just got one from slavens and wanted to get my carb tuned 100% before I switched so i could truly feel the difference. 

I have my carb super close to where I want it so im wondering if i need to go up in pilot or not... Thanks

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Farmboybunk:

funny you say that i was just going to ask what did you notice from stock xc cdi to sx300 cdi?

I just got one from slavens and wanted to get my carb tuned 100% before I switched so i could truly feel the difference. 

I have my carb super close to where I want it so im wondering if i need to go up in pilot or not... Thanks

Here’s two threads where I give my thoughts on the SX CDI.

The first one is early on after my first couple of rides and the second is after I get more time on it.

 

SX CDI for 300s

https://thumpertalk.com/applications/tapatalk/index.php?/topic/1289914-SX-CDI-for-300s

 

 

SX CDI in 17+ 250’s

https://thumpertalk.com/applications/tapatalk/index.php?/topic/1305116-SX-CDI-in-17%2B-250%E2%80%99s

 

After spending more time riding with the SX 300 CDI I have found that I needed to slightly richen the jetting on the bottom end. I’ve only just recently noticed it as the temperatures have become cooler in the lower elevation causing my bike to run slightly lean. Approximately 30 degree temperature change from when I installed during the hot summer months. It’s ever so slightly running lean now.

I did have it jetted spot on to slightly lean before adding the SX CDI. So if you are currently on the rich side, you may not have to touch jetting after installing a SX CDI.

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I have the 4-2M meter rod. I know they now recommend a 5-1 for our bikes, but my bikes running so good I have no desire to switch and try it. I’ll have to check what mm I have the rod set at.

I was mistaken on which meter rod I have. I check my meter rod last night and it’s stamped 4-2 and not 4-2M.

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when you have Kels on the phone ordering the RK Tek stuff, ask him his thoughts on what you need to do.  I would do that FIRST, before ordering any new carbs or anything else.  

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Im waiting on the sx300 head. Didnt want to use race gas because i ride too much and build mansions, dont own one. Am interested in the cdi also....just a 250sx cdi? And other changes?

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2 hours ago, hondaman331 said:

Im waiting on the sx300 head. Didnt want to use race gas because i ride too much and build mansions, dont own one. Am interested in the cdi also....just a 250sx cdi? And other changes?

There's a 300 SX CDI from past years that several have reported working fine on the '17+ bikes.  It's the same one that Slavens sells.

https://www.ktm-parts.com/SXS14300390.html

May end up a step richer on pilot jet.

Edited by redrider144
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There's a 300 SX CDI from past years that several have reported working fine on the '17+ bikes.  It's the same one that Slavens sells.
https://www.ktm-parts.com/SXS14300390.html
May end up a step richer on pilot jet.
I just dont want to run race gas. I can do 100ll avgas if necessary but I havent so far because i didnt want a yellow tank. Im thinking about sending the sx head and my cylinder to eric gorr racing for a pumpgas port/head job. If the ports are fine and i have to split or run straight avgas i think i could balance it....that stuff burns slow.

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21 minutes ago, hondaman331 said:

I just dont want to run race gas. I can do 100ll avgas if necessary but I havent so far because i didnt want a yellow tank. Im thinking about sending the sx head and my cylinder to eric gorr racing for a pumpgas port/head job. If the ports are fine and i have to split or run straight avgas i think i could balance it....that stuff burns slow.

You asked about the 250SX CDI.  It is not recommended to use that.  As far as I know there have been people running the 300SX CDI on pump gas.   Like @farmboybunk for example.  

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You asked about the 250SX CDI.  It is not recommended to use that.  As far as I know there have been people running the 300SX CDI on pump gas.   Like [mention=405699]farmboybunk[/mention] for example.  

Correct running 91 octane ethanol free with the SX 300 CDI (Part# SXS14300390). It’s the model Slaven’s sales.

Running RK Tek head set-up for 1,500 ft elevation and pump gas.

Have two bikes with the exact same set-up on 2017 XC 300’s.

Both bikes run great. Really impressed with power delivery and output.

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Correct running 91 octane ethanol free with the SX 300 CDI (Part# SXS14300390). It’s the model Slaven’s sells.
Running RK Tek head set-up for 1,500 ft elevation and pump gas.
Have two bikes with the exact same set-up on 2017 XC 300’s.
Both bikes run great. Really impressed with power delivery and output.
And that same cdi fits the 19 then? Any need for jetting changes? Im tuned extremely well as is currently.
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With the Jarvis mods I'm really happy with the oem carb in my 19.  I'm running an rk head specifically setup for my altitude, fuel, and lower curve preference (wide power band with lots of revs).  As part of the head setup it's intended to be installed with the cylinder spaced up to raise the ports slightly.  The results were great.  Power comes on a little stronger and earlier than stock and pulls longer.  I'm running the stock pv spring with very little preload.

Note I run race gas only.  I've found its more consistent and lets me really dial in jetting without having to worry about preignition.

Note th jarvis mods are critical, my bike was almost unrideable without them. Not enough signal over the pilot jet so it won't run right down low and not enough fuel to the main jet so it fell on its face up top.

I haven't tried a different cdi yet.  Mine is the tx so I have a map switch and in the aggressive map it's about all I want I think.  Super effective power, crisp and clean, pulls great but not out of control.  For reference I'm an A-ish rider riding Colorado single track primarily.  

Edited by bikepilot1

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