best engine mods for 2018 TC125?

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12/16/2018 10:01 AM

Hi, looking at making it faster. I already installed the Vforce,,and dialed the stock carb in with modified slide. Looking at pipes,silencers,porting,,or big bore and stroker crank? I also see new ECU from Athena. I'm an older c/b rider. I'm not looking for 2 hp gain in last 500 rpms and loose midrange pull. Looking for rider friendly increase as can be for 125. Thanks!

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12/16/2018 10:10 AM
Edited Date/Time: 12/16/2018 10:11 AM

I have the Vortex CDI, SXS head insert, Smart Carb, red PV spring and 49t rear sprocket on my 19 and it rips pretty good.

I wouldn't mind a long rod kit from F1, but that can wait till a full rebuild.

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12/16/2018 11:07 AM

The bike is pretty good stock, I am sure there is a little room for improvement but not a lot!

If you really want more power, just do the big bore. Once you start doing strokers or long rods etc. It can start getting complicated getting them to run properly

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12/16/2018 11:28 AM

FMF factory fatty and Shorty silencer. The 2.1 silencer is not as good. This combo adds 1.3 to peak and actually makes a little more torque. I've seen all the aftermarket pipes dyno'd and this combo was the only one significantly better than stock. HGS system was close but not as good.

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12/16/2018 12:21 PM

DynoDan22 wrote:

FMF factory fatty and Shorty silencer. The 2.1 silencer is not as good. This combo adds 1.3 to peak and actually makes a ...more

That's really good to know Dan, thanks.

What jetting was best on the dyno? Would you be able to post the chart?

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12/16/2018 2:04 PM

BR8ES wrote:

I have the Vortex CDI, SXS head insert, Smart Carb, red PV spring and 49t rear sprocket on my 19 and it rips pretty good.

I ...more

You mean the SXS Extreme Head Insert from the KTM Powerparts Katalog??

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12/16/2018 2:17 PM

riv187 wrote:

Hi, looking at making it faster. I already installed the Vforce,,and dialed the stock carb in with modified slide. Looking at ...more

Why you don’t buy the 150 Big Bore Zylinder from KTM, easy and simple modification

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12/16/2018 2:23 PM

What does the vortex CDI do?

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12/16/2018 3:00 PM

BR8ES wrote:

I have the Vortex CDI, SXS head insert, Smart Carb, red PV spring and 49t rear sprocket on my 19 and it rips pretty good.

I ...more

KTM Two Stroke wrote:

You mean the SXS Extreme Head Insert from the KTM Powerparts Katalog??

yes, that is the piece.

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12/16/2018 3:01 PM

opyguy wrote:

What does the vortex CDI do?

more flexibility with tuning and such. (different maps)

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12/16/2018 3:38 PM

BR8ES wrote:

I have the Vortex CDI, SXS head insert, Smart Carb, red PV spring and 49t rear sprocket on my 19 and it rips pretty good.

I ...more

KTM Two Stroke wrote:

You mean the SXS Extreme Head Insert from the KTM Powerparts Katalog??

BR8ES wrote:

yes, that is the piece.

Think about to buy one for my 150
Does it make any difference??

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12/16/2018 3:59 PM

Bruce372: I can't post the dyno graphs as the bike was dyno'd by a pipe manufacturer studying all the other pipes. The results were surprising. Some well known pipes actually lost a decent amount of power compared to stock. The shorty actually smoked all the standard length silencers and actually increased rev and over-rev (seems counterintuitive). We tried a ton of jetting but ended up on leaner on the main, two leaner on the pilot and stock needle position. The cylinder is very optimized from the factory and ever attempt to port it actually lost a tad bit of torque and the revs weren't worth it. Squish height is also pretty optimal from the factory. No huge gains unless you want to run uber-expensive MRX-02. For the average guy the KTM/Husky is pretty well optimized. My only suggestions are a Keihin carb from a '16 (factory jetting chart is very close if you mix at 40:1) the Keihin is just so stable and consistent and it makes more torque than the Mikuni. A Vforce 4 and FMF factory fatty/shorty is all that is needed to be close to 38hp on a Dynojet. That's pretty stout for a 125 on pump fuel and reasonable compression.

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12/16/2018 4:08 PM

KTM Two Stroke wrote:

You mean the SXS Extreme Head Insert from the KTM Powerparts Katalog??

BR8ES wrote:

yes, that is the piece.

KTM Two Stroke wrote:

Think about to buy one for my 150
Does it make any difference??

Definitely stronger than stock and cheap enough.

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12/16/2018 5:07 PM

Hey Dan, many thanks for that write up!

We are on the fatty with shorty and the V4 on our 2018 tc125 and a few holes in the airbox. On vp T2 ready mixed oxy fuel at 40.1 we went leaner on the pilot and least on the needle... northern cali summers. On the main, I actually went up one size I think.

The bike runs amazingly crisp and clean, I've rode it and my only complaint is that it looses a little overrev compared to other bikes (rm144 with mega top end porting).

I've heard similar reports about the kehin carb, but right now the bike runs so clean I've got no reason to start messing around. Kids these days dont know how lucky they are.

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12/16/2018 5:09 PM

Oh FWIW, I sent an fmf fatty and the buds hgs pipe to the dyno shop... on the 150 the hgs was a lot worse apart from the very top end. Fatty is a good pipe on the 150 also.

V force did nothing for power but we run it for reliability.

Squish gap on ours is 1.3mm, I might narrow it slightly on the next top end.

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12/16/2018 5:15 PM

These bikes are so well optimized to make the power they do, I am not surprised there isn't much room to improve them and its easy to make them worse with too much meddling.

There are many people that buy into the MXA BS that a 58mm piston 144 engine wont rev it makes me laugh. The ktm 150sx makes more power than the Japanese 250f, we have a 2005 ktm copy rm144 and it runs like an old motogp 125!

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12/16/2018 6:16 PM

Thanks so far for all the input! I was thinking of tightening squish to 1mm. I run straight 110 sunuco race gas. I also have searched for pictures of 19s “machined” power valve to see if I could duplicate it. Dynodan , was the fatty/shorty power better in the 8-11 range? That’s where I’ll gain on track. I saw a carb mod that cost a lot,,and claimed 2hp gain... whooo hooo 2hp!! ... but looking at dyno showed the motor was softer until 11,, then the stock carb tailed off last 500 rpms, and the modified carb stayed flat finishing 2 hp more at final same rpm. I can scream and fan clutch like next 125 rider,,, but realize I want broader power delivery.

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12/16/2018 6:19 PM

I’ve also thought about adding power jet. I don’t think it’s magic hp,, but tweaking it for max power before rolling up to start gate maybe beneficial.

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12/16/2018 6:28 PM

I have a old rm144, and know the 58mm piston gives some but takes away too..the new TM144 uses a 58mm stroke and the feedback is it has a wider , longer power delivery ... made me wonder if that’s a different direction to find power. It would be challenging to do,,, but I maybe able to do it myself,, and get Someone to port it to optimize.

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12/16/2018 7:05 PM

Riv187, the FMF gave nothing up on the front side and was better than stock from 8.5k on. The peak was up 1.3hp over stock and had the exact shape from peak to over-rev. The only way we got to 40.2hp was an ignition and MRX-02. We went through a few cylinders with slight porting to see what it liked and stock seemed the best overall.

Bruce372: we ran the squish at 1.15-1.20mm and the piston was barely below the deck at TDC (around 0.05mm or .0025". We didn't have an SXS head to try so I can't comment on that. The single ring piston only gained a little peak but made the power a tad narrower. We were surprised.

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12/17/2018 8:09 AM

DynoDan22 wrote:

Riv187, the FMF gave nothing up on the front side and was better than stock from 8.5k on. The peak was up 1.3hp over stock and ...more

Thanks, for the honesty. Which ignition picked up your bike?

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12/17/2018 12:45 PM

Riv187: Vortex

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2/8/2019 6:33 PM

Updates to my 2018 TC125. I got a new head insert from RK Tek. It's for race gas,,and boosted cranking compression stock from 153 up to 185lbs. I also picked up a used Buds HGS pipe and shorty style Buds silencer. A few blasts around the back yard and she felt different for sure. Being warned both changes would need richer jetting,,,I dug up a Power Jet kit I had for another project. The TMX is short body,,and little room to put it,,,and instructions said use JB weld to build up a spot for it. I TIG welded a mound and machined it off as a better solution to mounting the Power Jet. I have more confidence in the threads in aluminum. I dropped main from 490 to 460. Then opened the needle 3 turns and started ripping up the back yard. It's AWESOME. The needle is easy to reach down and twist to make tuning a breeze. I just kept making hits and turning in till the rich blubber cleaned up. My final setting adds up to a 540 total main size!!!! The pull from bottom up feels like a smooth steady power..I could trail ride at low revs,,,or scream this thing. It feels so linear and controllable. The bottom end is even nicer than before. Mine has the v force already,,,but the new additions of RK head, Buds exhaust, and Power jet feel like I got it all. Thanks Kelsey for the head in record time. I get to race this weekend and see how it goes in competition.

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2/8/2019 8:03 PM

riv187 wrote:

Updates to my 2018 TC125. I got a new head insert from RK Tek. It's for race gas,,and boosted cranking compression stock from ...more

Nice work, good to know about the RK insert. Thought he was only doing the 150s and above. Interesting about that Power Jet, I wouldn't mind trying a set up like that.

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2/8/2019 9:00 PM

Also for best performance don't run anymore octane then u have to. If you use too high of octane you'll lose power too

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2/9/2019 6:06 AM

ktm-5 wrote:

Also for best performance don't run anymore octane then u have to. If you use too high of octane you'll lose power too

I understand. This maybe the first 125 insert he done. I told it was for 110 race gas. Tore it down to give him exact deck height of piston. There isn't alot of jets over 500...my bike came with 500,520,540. Rather than order ones I'm missing I thought now was good time to use that PJ sitting on shelf.

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2/9/2019 9:39 AM
Edited Date/Time: 2/9/2019 4:55 PM

Is this the Lectron power jet adapted for the Mikuni? How is the other end attached? Pretty interested in this for experimentation.

edit- I see it is a Vito Power Jet Kit, I may give this a shot.

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2/11/2019 6:29 AM
Edited Date/Time: 2/11/2019 6:40 AM

BR8ES wrote:

Is this the Lectron power jet adapted for the Mikuni? How is the other end attached? Pretty interested in this for ...more

I do not have a lectron,,,but the adaption should work. The fuel is drawn from a nipple in bottom rear corner of bowl, up through line to the jet. The jet needs to be 10 oclock-2 oclock positioned. The lectron already is adjustable so this maybe overkill.

I like the ease at adjusting this...I can just reach under like I'm turning the choke while riding,,,make a adjustment,,and gas it again and feel the change,,,and repeat till I feel the ideal top end. I'm not running through all the gears either,,,just 1st/2nd is enough to know.

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2/11/2019 11:14 AM

Do you have a 250 also? I'm trying to find the stock compression range for a '18 250 so I can see what mine is currently at.

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2018 KTM 250sx
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2/12/2019 3:14 PM

AJ565 wrote:

Do you have a 250 also? I'm trying to find the stock compression range for a '18 250 so I can see what mine is currently at.

Yes AJ565 I have a 17 TC250 as well as the 18 TC125. I checked the 250 compression today and it is 192psi cold ,here at 200 ft,,,and with a Lisle compression gauge. My 250 has 12.5 hrs,,,and not been apart. I was surprised at the high number! Let me know what yours measures and hrs on your motor.

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