TC125 Exhaust Systems

TLD_KTM_13
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TLD_KTM_13
I'm getting a brand new TC 125 and want to get max horsepower out of it. I've always only run FMF, but my contract with them kinda got screwed up this year so I'm a free man, and I want the most horsepower this engine can legally get. Any help? Dynos appreciado
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FGR01
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FGR01 6/30/2021 7:45am
6/30/2021 7:45am
Don't have a dyno and can only give ass-dyno info. On my 2021 TC125 I've tried the Stock, Bill's cone with Bill's carbon MX2, and FMF Factory Fatty with standard length powercore. Generally, I will say I did not notice much difference between any of the pipes. About the only difference is the Bill's MX2 muffler is almost a shorty so it felt punchier than the stock or powercore, which are basically the same length as each other. Holding the Bills pipe and FMF Factory next to each other, they look like copies. Appear to be the same dimensions. Guys are going to get on here and rave about the PC shorty. It sounds like crap to me and the shorties fall off the power on top.

If you want max power, plan to be in the carb. Either use the jetting specs from the long thread in the Mikuni or plan to do a Keihin with a STIC.
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TLD_KTM_13
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TLD_KTM_13 6/30/2021 7:48am
6/30/2021 7:48am
FGR01 wrote:
Don't have a dyno and can only give ass-dyno info. On my 2021 TC125 I've tried the Stock, Bill's cone with Bill's carbon MX2, and FMF...
Don't have a dyno and can only give ass-dyno info. On my 2021 TC125 I've tried the Stock, Bill's cone with Bill's carbon MX2, and FMF Factory Fatty with standard length powercore. Generally, I will say I did not notice much difference between any of the pipes. About the only difference is the Bill's MX2 muffler is almost a shorty so it felt punchier than the stock or powercore, which are basically the same length as each other. Holding the Bills pipe and FMF Factory next to each other, they look like copies. Appear to be the same dimensions. Guys are going to get on here and rave about the PC shorty. It sounds like crap to me and the shorties fall off the power on top.

If you want max power, plan to be in the carb. Either use the jetting specs from the long thread in the Mikuni or plan to do a Keihin with a STIC.
Honestly dude, you're right. Most of these are about the same, so I'll probably go for badass looks, like the Scalvini cone or the Bills cone with some sort of silencer from the same.
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sandman768
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sandman768 6/30/2021 8:21am
6/30/2021 8:21am
I’m in same boat, waiting on a KTM 125 SX . I have always had good results with FmF pipes but would like to see some dyno numbers from the pipe producers. These bikes seem to have a pretty solid package stock, but I like to keep the stock pipe new for when I sell it. I”m guessing gearing & jetting will offer the most performance. It might come down to who actually has a pipe available for purchase….most seem back ordered.
Rickyisms 6/30/2021 8:35am
6/30/2021 8:35am
I run the PC works and R304, my motor is built by PC now but in stock form the system really helped bridge the gap between low to mid and made the mid to top very smooth and linear with a pretty good add-on to the already great pulling power of these bikes. I think the R304 shorty sounds great, reminds me a lot of a 90s 125 with a stinger pipe.
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Rickyisms 6/30/2021 8:40am
6/30/2021 8:40am
Max horsepower though? Send your cylinder to Lynks or PC, run a STIC, jet for good fuel and let it rip. In my experience with these bikes the gains are minimal at best with a full system.
TLD_KTM_13
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TLD_KTM_13 6/30/2021 9:23am
6/30/2021 9:23am
Rickyisms wrote:
I run the PC works and R304, my motor is built by PC now but in stock form the system really helped bridge the gap between...
I run the PC works and R304, my motor is built by PC now but in stock form the system really helped bridge the gap between low to mid and made the mid to top very smooth and linear with a pretty good add-on to the already great pulling power of these bikes. I think the R304 shorty sounds great, reminds me a lot of a 90s 125 with a stinger pipe.
Should I trust someone who claims diesel taste the best?
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FGR01
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FGR01 6/30/2021 9:55am
6/30/2021 9:55am
So, my bike is stock other than the exhaust, jetting, V4, and vented airbox. Recently met a guy at the track with same bike with a full built motor from a very well known reputable builder. And I mean VERY well known. And he had the PC shorty and Keihin, not sure if STIC or not. Anyway, my buddy rode the 2 bikes back to back and so did the owner of the other bike. Both agreed mine ran better. What I take away from this is that proper jetting is by far the most important thing. You'll lose more with slightly off jetting than you'll ever gain with a pipe on these bikes.
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Rickyisms 6/30/2021 11:50am
6/30/2021 11:50am
FGR01 wrote:
So, my bike is stock other than the exhaust, jetting, V4, and vented airbox. Recently met a guy at the track with same bike with a...
So, my bike is stock other than the exhaust, jetting, V4, and vented airbox. Recently met a guy at the track with same bike with a full built motor from a very well known reputable builder. And I mean VERY well known. And he had the PC shorty and Keihin, not sure if STIC or not. Anyway, my buddy rode the 2 bikes back to back and so did the owner of the other bike. Both agreed mine ran better. What I take away from this is that proper jetting is by far the most important thing. You'll lose more with slightly off jetting than you'll ever gain with a pipe on these bikes.
The Mikuni is for sure a better carb once jetted properly, maybe slightly more finicky than the Keihin, but the power difference is there once you get the Mikuni dialed. I stuck with the Keihin due to the Mikuni wanting to be rejetted depending on the humidity down here in FL. I got tired of messing with it and stuck with the Keihin.
Tracktor
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Tracktor 6/30/2021 12:23pm
6/30/2021 12:23pm
No mod will come close to a 38mm keihin Carby with STIC Metering block. We've done a ton of back to back testing pipes/ported cylinders/stuffed cases/etc....I've let quite a few people test them and every one has bought one after using....(no affiliation with them other than believe in product 100%)...
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sandman768
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sandman768 6/30/2021 1:05pm
6/30/2021 1:05pm
Tracktor wrote:
No mod will come close to a 38mm keihin Carby with STIC Metering block. We've done a ton of back to back testing pipes/ported cylinders/stuffed cases/etc....I've...
No mod will come close to a 38mm keihin Carby with STIC Metering block. We've done a ton of back to back testing pipes/ported cylinders/stuffed cases/etc....I've let quite a few people test them and every one has bought one after using....(no affiliation with them other than believe in product 100%)...
Who are you getting that from?
fredmotokx 6/30/2021 1:55pm
6/30/2021 1:55pm
Tracktor wrote:
No mod will come close to a 38mm keihin Carby with STIC Metering block. We've done a ton of back to back testing pipes/ported cylinders/stuffed cases/etc....I've...
No mod will come close to a 38mm keihin Carby with STIC Metering block. We've done a ton of back to back testing pipes/ported cylinders/stuffed cases/etc....I've let quite a few people test them and every one has bought one after using....(no affiliation with them other than believe in product 100%)...
For the price, it did cost me to get the jetting right from @AJ565 thread, not seeing myself spend 800 bucks to get the combo your saying. The bike is awesome now.
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Tracktor 6/30/2021 2:25pm
6/30/2021 2:25pm
Tracktor wrote:
No mod will come close to a 38mm keihin Carby with STIC Metering block. We've done a ton of back to back testing pipes/ported cylinders/stuffed cases/etc....I've...
No mod will come close to a 38mm keihin Carby with STIC Metering block. We've done a ton of back to back testing pipes/ported cylinders/stuffed cases/etc....I've let quite a few people test them and every one has bought one after using....(no affiliation with them other than believe in product 100%)...
sandman768 wrote:
Who are you getting that from?
Getting what from?.........
Tracktor
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Tracktor 6/30/2021 2:32pm
6/30/2021 2:32pm
Tracktor wrote:
No mod will come close to a 38mm keihin Carby with STIC Metering block. We've done a ton of back to back testing pipes/ported cylinders/stuffed cases/etc....I've...
No mod will come close to a 38mm keihin Carby with STIC Metering block. We've done a ton of back to back testing pipes/ported cylinders/stuffed cases/etc....I've let quite a few people test them and every one has bought one after using....(no affiliation with them other than believe in product 100%)...
fredmotokx wrote:
For the price, it did cost me to get the jetting right from @AJ565 thread, not seeing myself spend 800 bucks to get the combo your...
For the price, it did cost me to get the jetting right from @AJ565 thread, not seeing myself spend 800 bucks to get the combo your saying. The bike is awesome now.
Why spend $800? Used Airstrykers all over Ebay for $150 or less + STIC $300. It's tough to believe the difference without riding it however. Best description is a 4-stroke 2-stroke.

On our 18 TC125's we ran Mikuni then Keihin and it was better. Then put STIC in and my kid flipped at the difference. Back to back blind testing. Then bought another TC with $3500 into the engine with $0 hours on it. Stock bike with STIC still blew it away. Much broader powerband plus substantial over-rev.

To each their own but every time I've let someone borrow one they have gone out and paid the $$ right away. I've bought 6 so far personally and running them in everything from my 87 Cr250 to my 96 Cr125 & our TC's.........
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FGR01 6/30/2021 4:14pm
6/30/2021 4:14pm
Rickyisms wrote:
The Mikuni is for sure a better carb once jetted properly, maybe slightly more finicky than the Keihin, but the power difference is there once you...
The Mikuni is for sure a better carb once jetted properly, maybe slightly more finicky than the Keihin, but the power difference is there once you get the Mikuni dialed. I stuck with the Keihin due to the Mikuni wanting to be rejetted depending on the humidity down here in FL. I got tired of messing with it and stuck with the Keihin.
After getting my Mikuni dialed with the jetting from the thread and then my small tweaks it is very stable, not finicky at all. I've had the bike a year now and have ridden it from 40-108 degrees, and from 600 - 5,000ft and from 2% - 65% humidity. The only adjustments I need to make for the extremes are between a 35 and 37.5 pilot and fine tune with either the 42-74 or 42-73 needle on 2nd or 3rd clip. As we've started to get stupid hot here lately, I expected it to get rich and blubbery but it just keeps ripping. Still running a 540 main, same as when it is cold out.
sandman768
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sandman768 6/30/2021 4:36pm
6/30/2021 4:36pm
Tracktor wrote:
Getting what from?.........
The carb with the stic?
Bruce372
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Bruce372 6/30/2021 4:58pm
6/30/2021 4:58pm Edited Date/Time 6/30/2021 4:59pm
Most companies won't show dynos since their parts actually loose power over stock. For sure, aftermarket stuff rarely fits properly.

one exception is the stic, where independent dyno shows much bigger improvement over many other bolt on parts, both with pick up and over rev.

The port timing on the 125 vs 150 should be similar, given they run the same crank, so pipes should work the same on either engine... however, where I've found it come undone is the silencer....

I buikt a rm265, and it was a dog, like a rag in the airbox. Swapped put thr PC shorty for the stock silencer back on and it transformed it.

On the other hand, I supplied a bunch of parts to a friend with dyno access... the pc shorty on th 150 was the only silencer that didn't loose power over stock! So I bought that and didn't try others.

Nonetheless, it's silly, 125s don't make a lot of power, so spending all that money for 1HP gain isn't going to change much. Get the bike jetted crisp and hold it wide open. If it's still too slow, get a 450 lol
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FGR01 6/30/2021 9:26pm
6/30/2021 9:26pm
Bruce372 wrote:
Most companies won't show dynos since their parts actually loose power over stock. For sure, aftermarket stuff rarely fits properly. one exception is the stic, where...
Most companies won't show dynos since their parts actually loose power over stock. For sure, aftermarket stuff rarely fits properly.

one exception is the stic, where independent dyno shows much bigger improvement over many other bolt on parts, both with pick up and over rev.

The port timing on the 125 vs 150 should be similar, given they run the same crank, so pipes should work the same on either engine... however, where I've found it come undone is the silencer....

I buikt a rm265, and it was a dog, like a rag in the airbox. Swapped put thr PC shorty for the stock silencer back on and it transformed it.

On the other hand, I supplied a bunch of parts to a friend with dyno access... the pc shorty on th 150 was the only silencer that didn't loose power over stock! So I bought that and didn't try others.

Nonetheless, it's silly, 125s don't make a lot of power, so spending all that money for 1HP gain isn't going to change much. Get the bike jetted crisp and hold it wide open. If it's still too slow, get a 450 lol
Exactly. Also, been said many times.. we race/ride on the track, not on the dyno. Or put another way, Dyno pulls are done in 4th gear, WFO from the bottom of the rev range to the top. How many times do you do this on a track? Almost never. So, even if a certain pipe/muffler adds 1HP, that is only at WFO at the peak of power. The dyno doesn't tell you part throttle differences nor does the dyno care about a lean bog or rich blubber at the crack of the throttle but you will care coming out of every corner on the track.
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Bruce372
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Bruce372 6/30/2021 9:46pm
6/30/2021 9:46pm
Bruce372 wrote:
Most companies won't show dynos since their parts actually loose power over stock. For sure, aftermarket stuff rarely fits properly. one exception is the stic, where...
Most companies won't show dynos since their parts actually loose power over stock. For sure, aftermarket stuff rarely fits properly.

one exception is the stic, where independent dyno shows much bigger improvement over many other bolt on parts, both with pick up and over rev.

The port timing on the 125 vs 150 should be similar, given they run the same crank, so pipes should work the same on either engine... however, where I've found it come undone is the silencer....

I buikt a rm265, and it was a dog, like a rag in the airbox. Swapped put thr PC shorty for the stock silencer back on and it transformed it.

On the other hand, I supplied a bunch of parts to a friend with dyno access... the pc shorty on th 150 was the only silencer that didn't loose power over stock! So I bought that and didn't try others.

Nonetheless, it's silly, 125s don't make a lot of power, so spending all that money for 1HP gain isn't going to change much. Get the bike jetted crisp and hold it wide open. If it's still too slow, get a 450 lol
FGR01 wrote:
Exactly. Also, been said many times.. we race/ride on the track, not on the dyno. Or put another way, Dyno pulls are done in 4th gear...
Exactly. Also, been said many times.. we race/ride on the track, not on the dyno. Or put another way, Dyno pulls are done in 4th gear, WFO from the bottom of the rev range to the top. How many times do you do this on a track? Almost never. So, even if a certain pipe/muffler adds 1HP, that is only at WFO at the peak of power. The dyno doesn't tell you part throttle differences nor does the dyno care about a lean bog or rich blubber at the crack of the throttle but you will care coming out of every corner on the track.
The problem with dynos, they don't care you spent $400 on a new pipe and reeds, humans feedback will be subjective and influence by many factors. I am willing to bet, if you don't like the sound of the silencer it will influence whether you feel it performs better. On the 150, the dyno didn't say the PC shorty is better than stock, but it did say that others were worse!

It's funny, the runs my tuner did showed the mikuni have best carburettion and afr, you can feel it, that carb is so crisp and clean when setup. That said, the stic makes significantly more power at partial throttle and you can definitely feel that when riding.

If I bought a new stock 2022 sx125tc, the only mod I would do would be the stic keihin.
Bruce372
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Bruce372 6/30/2021 9:48pm
6/30/2021 9:48pm
Btw, I just put new graphics on my bike. It looks amazing and I know it's gonna ride even better 😀
FGR01
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FGR01 6/30/2021 9:56pm
6/30/2021 9:56pm
Bruce372 wrote:
Most companies won't show dynos since their parts actually loose power over stock. For sure, aftermarket stuff rarely fits properly. one exception is the stic, where...
Most companies won't show dynos since their parts actually loose power over stock. For sure, aftermarket stuff rarely fits properly.

one exception is the stic, where independent dyno shows much bigger improvement over many other bolt on parts, both with pick up and over rev.

The port timing on the 125 vs 150 should be similar, given they run the same crank, so pipes should work the same on either engine... however, where I've found it come undone is the silencer....

I buikt a rm265, and it was a dog, like a rag in the airbox. Swapped put thr PC shorty for the stock silencer back on and it transformed it.

On the other hand, I supplied a bunch of parts to a friend with dyno access... the pc shorty on th 150 was the only silencer that didn't loose power over stock! So I bought that and didn't try others.

Nonetheless, it's silly, 125s don't make a lot of power, so spending all that money for 1HP gain isn't going to change much. Get the bike jetted crisp and hold it wide open. If it's still too slow, get a 450 lol
FGR01 wrote:
Exactly. Also, been said many times.. we race/ride on the track, not on the dyno. Or put another way, Dyno pulls are done in 4th gear...
Exactly. Also, been said many times.. we race/ride on the track, not on the dyno. Or put another way, Dyno pulls are done in 4th gear, WFO from the bottom of the rev range to the top. How many times do you do this on a track? Almost never. So, even if a certain pipe/muffler adds 1HP, that is only at WFO at the peak of power. The dyno doesn't tell you part throttle differences nor does the dyno care about a lean bog or rich blubber at the crack of the throttle but you will care coming out of every corner on the track.
Bruce372 wrote:
The problem with dynos, they don't care you spent $400 on a new pipe and reeds, humans feedback will be subjective and influence by many factors...
The problem with dynos, they don't care you spent $400 on a new pipe and reeds, humans feedback will be subjective and influence by many factors. I am willing to bet, if you don't like the sound of the silencer it will influence whether you feel it performs better. On the 150, the dyno didn't say the PC shorty is better than stock, but it did say that others were worse!

It's funny, the runs my tuner did showed the mikuni have best carburettion and afr, you can feel it, that carb is so crisp and clean when setup. That said, the stic makes significantly more power at partial throttle and you can definitely feel that when riding.

If I bought a new stock 2022 sx125tc, the only mod I would do would be the stic keihin.
Yes, I agree.. dyno is objective and rider is subjective (mostly.. if you notice a lean bog.. it is there for a fact. That is not subjective).

But the point is, even if a dyno objectively proves something makes more (or less) power, that does not mean that it is necessarily better or worse on the track. Good example is the YZ250F and 450F. Everyone who rides them raves about how powerful they are. But their dyno numbers are actually not that impressive. Usable power that actually works on the track is what matters and is not what the dyno necessarily quantifies.
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FGR01 7/1/2021 6:46am
7/1/2021 6:46am
Another thing to add to this thread for all you guys messing with your exhaust and jetting, make sure you get a PV adjustment tool and play with the PV adjustment after you've made all your other changes.

Basically, every bike seems to come with a different setting on the PV adjustment and it is tailored to the stock jetting and stock exhaust in that bike. Once you change something, it is best to re-adjust your PV to get this matched/synched to the changes you've made. It has a big impact on power delivery. 3/4 - 1 turn in either direction can be the difference between power that is really punchy and lights up the rear tire on hardpack or power that is smoother and pulls much broader and longer. It's kind of a personal preference thing. No single setting is absolutely best for everyone or every track.
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Tracktor 7/1/2021 1:00pm
7/1/2021 1:00pm Edited Date/Time 7/1/2021 1:02pm
Hammer 663s wrote:
https://www.tokyooffroad.com/product/stic-keihin-pwk-38mm-air-striker-s…
sandman768 wrote:
Thanks
I buy used carbs off Ebay usually. The 38mm Airstryker was a hugely popular OEM carb on many bikes in late '90's until today. If has TPS or powerjet they are easy to modify so not used. Best bet is a newer YZ250 carb or 16-older (not sure what year they started short body) KTM 125. You just want a short body (although I've used a long body on a TC125 for awhile with a couple mods) 38mm not 36mm. You can tell those two apart by the intake. 38mm is symmetrical while 36 is offset.............STIC I buy straight from George at http://www.sticsupertorque.com/ he sells carbs also if just want whole thing. And a wealth of info too if you get him on phone....
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FGR01 7/1/2021 3:16pm
7/1/2021 3:16pm
If you're putting a Keihin on the 2017 and newer 125/150, I suggest also using the rubber manifold from the 2016 bike. If you look a the sealing grooves on the front of a Keihin versus the Mikuni you'll see they are not the same. The rubber manifold is molded according to the carb it was intended for. The Keihin will go in the newer manifold, and it might seal somewhat OK. and I'm sure there are folks running like this long term, but it's not ideal and seems like a potential point to leak.
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