49t sprocket on a TC125?

JB28
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JB28
Edited Date/Time 5/13/2019 1:42pm
I have a 2017 tc125. Stock engine and stock front sprocket. Will going down a tooth in the rear make maintaining the power band harder or easier, as the bike goes in and out of it quick
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Falcon
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Falcon 4/29/2019 4:14pm
4/29/2019 4:14pm
Smaller rear sprocket = faster top speed but less acceleration. It's like riding in half a gear higher. It will make it more difficult to keep the bike on the pipe.
If you want to make it slightly easier to get on the pipe and enjoy more instant acceleration, go larger on the rear sprocket. This would reduce your top speed.

Changes to the front sprocket would have the reverse effect. A smaller front is like downshifting (easier to get on the pipe,) and a larger front is like upshifting (more top speed).

A one tooth change in the front is equivalent to about three teeth on the rear.
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BR8ES
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BR8ES 4/29/2019 4:37pm
4/29/2019 4:37pm
I really enjoy a 49 on my 19 TC125, just more spread for the gears.
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Bruce372
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Bruce372 4/29/2019 7:19pm
4/29/2019 7:19pm
For $40 on a new sprocket, you might as well.just try it
CarlinoJoeVideo
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CarlinoJoeVideo 5/2/2019 6:19am
5/2/2019 6:19am
I think a 49 would be too small on the 125. Personally I have more problems with not enough torque and being in the wrong gear in a corner. But if you could be thru the corners with 49 maybe shift less?

51 would make it easier to be always on the pipe but maybe shift sooner.
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ThatOneKid
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ThatOneKid 5/2/2019 7:05am
5/2/2019 7:05am
Not quite apples to apples, but my 150 came with a 48t sprocket and I went up to a 49t which made carrying 3rd in corners much easier without so much clutch. If you want it to be easier to stay on the pipe i'd try a 51t on your 125.

Don't forget to mess with the powervalve adjuster too, you can shift your power a bit that way as well.
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JB28
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JB28 5/2/2019 2:28pm
5/2/2019 2:28pm
ThatOneKid wrote:
Not quite apples to apples, but my 150 came with a 48t sprocket and I went up to a 49t which made carrying 3rd in corners...
Not quite apples to apples, but my 150 came with a 48t sprocket and I went up to a 49t which made carrying 3rd in corners much easier without so much clutch. If you want it to be easier to stay on the pipe i'd try a 51t on your 125.

Don't forget to mess with the powervalve adjuster too, you can shift your power a bit that way as well.
I’ve always been curious as to how to adjust the power valve. In regard to how much, in what direction, does what? Maybe I’ll start messing with that a bit to to maybe get the spread I want, with the early hitting power. Its hard enough trying to keep up with the Loretta guys on modded 250s our of corners. I just want the power to be there. It has enough. Just hard to maintain even when pinned and riding high rpm. I can’t quite pinpoint where the adjustment needs to be made. Carb tuning? Gearing? Power valve? Or a combination of all. It’s my first two stroke since the minis. And I got it to train on.
CarlinoJoeVideo
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CarlinoJoeVideo 5/2/2019 9:43pm
5/2/2019 9:43pm
On the right side case there’s a square bolt. If you turn it all the way counter clockwise it will stop. At that setting the power valve will open sooner so it will feel like more bottom end, but you don’t have as much on the top end. The more you turn it clockwise the the later it will open and start giving you farther pull on the top end.

I typically run 1.5-1.75 turns in. Try adjusting yours .5 turns until you get the right feel.

I also run a JD Jet kit.
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ThatOneKid
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ThatOneKid 5/3/2019 7:16am
5/3/2019 7:16am Edited Date/Time 5/3/2019 7:18am
ThatOneKid wrote:
Not quite apples to apples, but my 150 came with a 48t sprocket and I went up to a 49t which made carrying 3rd in corners...
Not quite apples to apples, but my 150 came with a 48t sprocket and I went up to a 49t which made carrying 3rd in corners much easier without so much clutch. If you want it to be easier to stay on the pipe i'd try a 51t on your 125.

Don't forget to mess with the powervalve adjuster too, you can shift your power a bit that way as well.
JB28 wrote:
I’ve always been curious as to how to adjust the power valve. In regard to how much, in what direction, does what? Maybe I’ll start messing...
I’ve always been curious as to how to adjust the power valve. In regard to how much, in what direction, does what? Maybe I’ll start messing with that a bit to to maybe get the spread I want, with the early hitting power. Its hard enough trying to keep up with the Loretta guys on modded 250s our of corners. I just want the power to be there. It has enough. Just hard to maintain even when pinned and riding high rpm. I can’t quite pinpoint where the adjustment needs to be made. Carb tuning? Gearing? Power valve? Or a combination of all. It’s my first two stroke since the minis. And I got it to train on.
In addition to Joe's powervalve advise, putting an FMF fatty and powercore 2.1 silencer (its shorter than stock but longer than a shorty) defintiely woke up the bottom end on my bike, and added some power on top. It pulls noticeably harder in 3rd coming out of turns and i need minimal clutch as long as i don't come to a dead stop.

I've also heard of Husky guys drilling holes in the left side number plates since the airbox is a bit more restricted and choked up than the KTMs. That also wakes the bike up.
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JB28
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JB28 5/5/2019 9:39am
5/5/2019 9:39am
CarlinoJoeVideo wrote:
On the right side case there’s a square bolt. If you turn it all the way counter clockwise it will stop. At that setting the power...
On the right side case there’s a square bolt. If you turn it all the way counter clockwise it will stop. At that setting the power valve will open sooner so it will feel like more bottom end, but you don’t have as much on the top end. The more you turn it clockwise the the later it will open and start giving you farther pull on the top end.

I typically run 1.5-1.75 turns in. Try adjusting yours .5 turns until you get the right feel.

I also run a JD Jet kit.
Thanks man. I’ll definitely do that. The power valve seemed like a useful tool. I just never touched it because of the lack of knowledge I have for it and there’s nothing in the manual about it. That’s exactly what I wanted to know. Thanks
JB28
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JB28 5/5/2019 9:46am
5/5/2019 9:46am
ThatOneKid wrote:
Not quite apples to apples, but my 150 came with a 48t sprocket and I went up to a 49t which made carrying 3rd in corners...
Not quite apples to apples, but my 150 came with a 48t sprocket and I went up to a 49t which made carrying 3rd in corners much easier without so much clutch. If you want it to be easier to stay on the pipe i'd try a 51t on your 125.

Don't forget to mess with the powervalve adjuster too, you can shift your power a bit that way as well.
JB28 wrote:
I’ve always been curious as to how to adjust the power valve. In regard to how much, in what direction, does what? Maybe I’ll start messing...
I’ve always been curious as to how to adjust the power valve. In regard to how much, in what direction, does what? Maybe I’ll start messing with that a bit to to maybe get the spread I want, with the early hitting power. Its hard enough trying to keep up with the Loretta guys on modded 250s our of corners. I just want the power to be there. It has enough. Just hard to maintain even when pinned and riding high rpm. I can’t quite pinpoint where the adjustment needs to be made. Carb tuning? Gearing? Power valve? Or a combination of all. It’s my first two stroke since the minis. And I got it to train on.
ThatOneKid wrote:
In addition to Joe's powervalve advise, putting an FMF fatty and powercore 2.1 silencer (its shorter than stock but longer than a shorty) defintiely woke up...
In addition to Joe's powervalve advise, putting an FMF fatty and powercore 2.1 silencer (its shorter than stock but longer than a shorty) defintiely woke up the bottom end on my bike, and added some power on top. It pulls noticeably harder in 3rd coming out of turns and i need minimal clutch as long as i don't come to a dead stop.

I've also heard of Husky guys drilling holes in the left side number plates since the airbox is a bit more restricted and choked up than the KTMs. That also wakes the bike up.
I currently have a bills mx2 silencer and love it. Sounds crispy and woke my bottom end up. I forgot about the air box thing. It was on my to do list when I got the bike. And simply never got around to it. With the combination of the powevalve adjustments, more airflow, and smaller sprocket in the rear I should be able to find usable power when I want it now. thanks guys.
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AJ565 5/5/2019 5:29pm
5/5/2019 5:29pm
I rode a 150 and a 125 today both with a 50t sprocket. I think a 49t would be much better on both to help not have to shift so much. It took me a few laps to get used to down shifting at least 2 gears going into a corner lol.
BR8ES
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BR8ES 5/5/2019 6:08pm
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AJ565 wrote:
I rode a 150 and a 125 today both with a 50t sprocket. I think a 49t would be much better on both to help not...
I rode a 150 and a 125 today both with a 50t sprocket. I think a 49t would be much better on both to help not have to shift so much. It took me a few laps to get used to down shifting at least 2 gears going into a corner lol.
yep...49t works great. Can't imagine going the other way.
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IanMac138 5/12/2019 10:00pm
5/12/2019 10:00pm
CarlinoJoeVideo wrote:
On the right side case there’s a square bolt. If you turn it all the way counter clockwise it will stop. At that setting the power...
On the right side case there’s a square bolt. If you turn it all the way counter clockwise it will stop. At that setting the power valve will open sooner so it will feel like more bottom end, but you don’t have as much on the top end. The more you turn it clockwise the the later it will open and start giving you farther pull on the top end.

I typically run 1.5-1.75 turns in. Try adjusting yours .5 turns until you get the right feel.

I also run a JD Jet kit.
JB28 wrote:
Thanks man. I’ll definitely do that. The power valve seemed like a useful tool. I just never touched it because of the lack of knowledge I...
Thanks man. I’ll definitely do that. The power valve seemed like a useful tool. I just never touched it because of the lack of knowledge I have for it and there’s nothing in the manual about it. That’s exactly what I wanted to know. Thanks
The power valve is incredible for tuning the delivery of power. I installed the Slavens HV Lectron with 2.1 Powercore silencer and 49 tooth rear sprocket (13/48 stock) on my 19 150SX and reset the power valve to 1.75 turns in and wow...made all the difference in the world. Stock power valve setting was at 3 in and was just way too gnarly of a hit at what seemed like the worst time approaching the faces of jumps out of corners. Now my bike is dialed and my confidence on it instantly transformed.
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BR8ES
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BR8ES 5/13/2019 3:14am
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CarlinoJoeVideo wrote:
On the right side case there’s a square bolt. If you turn it all the way counter clockwise it will stop. At that setting the power...
On the right side case there’s a square bolt. If you turn it all the way counter clockwise it will stop. At that setting the power valve will open sooner so it will feel like more bottom end, but you don’t have as much on the top end. The more you turn it clockwise the the later it will open and start giving you farther pull on the top end.

I typically run 1.5-1.75 turns in. Try adjusting yours .5 turns until you get the right feel.

I also run a JD Jet kit.
JB28 wrote:
Thanks man. I’ll definitely do that. The power valve seemed like a useful tool. I just never touched it because of the lack of knowledge I...
Thanks man. I’ll definitely do that. The power valve seemed like a useful tool. I just never touched it because of the lack of knowledge I have for it and there’s nothing in the manual about it. That’s exactly what I wanted to know. Thanks
IanMac138 wrote:
The power valve is incredible for tuning the delivery of power. I installed the Slavens HV Lectron with 2.1 Powercore silencer and 49 tooth rear sprocket...
The power valve is incredible for tuning the delivery of power. I installed the Slavens HV Lectron with 2.1 Powercore silencer and 49 tooth rear sprocket (13/48 stock) on my 19 150SX and reset the power valve to 1.75 turns in and wow...made all the difference in the world. Stock power valve setting was at 3 in and was just way too gnarly of a hit at what seemed like the worst time approaching the faces of jumps out of corners. Now my bike is dialed and my confidence on it instantly transformed.
PV set from where? Full out, flush with housing, etc?
Glad someone else runs a 49t besides me.
CarlinoJoeVideo
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CarlinoJoeVideo 5/13/2019 7:35am
5/13/2019 7:35am
JB28 wrote:
Thanks man. I’ll definitely do that. The power valve seemed like a useful tool. I just never touched it because of the lack of knowledge I...
Thanks man. I’ll definitely do that. The power valve seemed like a useful tool. I just never touched it because of the lack of knowledge I have for it and there’s nothing in the manual about it. That’s exactly what I wanted to know. Thanks
IanMac138 wrote:
The power valve is incredible for tuning the delivery of power. I installed the Slavens HV Lectron with 2.1 Powercore silencer and 49 tooth rear sprocket...
The power valve is incredible for tuning the delivery of power. I installed the Slavens HV Lectron with 2.1 Powercore silencer and 49 tooth rear sprocket (13/48 stock) on my 19 150SX and reset the power valve to 1.75 turns in and wow...made all the difference in the world. Stock power valve setting was at 3 in and was just way too gnarly of a hit at what seemed like the worst time approaching the faces of jumps out of corners. Now my bike is dialed and my confidence on it instantly transformed.
BR8ES wrote:
PV set from where? Full out, flush with housing, etc?
Glad someone else runs a 49t besides me.
I might try the 49 now. Hahaha!

PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out.

I agree with Ian, at that 1.75 (turns in) its very ridable.
BR8ES
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BR8ES 5/13/2019 10:47am
5/13/2019 10:47am
IanMac138 wrote:
The power valve is incredible for tuning the delivery of power. I installed the Slavens HV Lectron with 2.1 Powercore silencer and 49 tooth rear sprocket...
The power valve is incredible for tuning the delivery of power. I installed the Slavens HV Lectron with 2.1 Powercore silencer and 49 tooth rear sprocket (13/48 stock) on my 19 150SX and reset the power valve to 1.75 turns in and wow...made all the difference in the world. Stock power valve setting was at 3 in and was just way too gnarly of a hit at what seemed like the worst time approaching the faces of jumps out of corners. Now my bike is dialed and my confidence on it instantly transformed.
BR8ES wrote:
PV set from where? Full out, flush with housing, etc?
Glad someone else runs a 49t besides me.
CarlinoJoeVideo wrote:
I might try the 49 now. Hahaha! PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out. I...
I might try the 49 now. Hahaha!

PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out.

I agree with Ian, at that 1.75 (turns in) its very ridable.
Thanks for the PV info, gonna try that this weekend!
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IanMac138 5/13/2019 11:08am
5/13/2019 11:08am
BR8ES wrote:
PV set from where? Full out, flush with housing, etc?
Glad someone else runs a 49t besides me.
CarlinoJoeVideo wrote:
I might try the 49 now. Hahaha! PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out. I...
I might try the 49 now. Hahaha!

PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out.

I agree with Ian, at that 1.75 (turns in) its very ridable.
BR8ES wrote:
Thanks for the PV info, gonna try that this weekend!
Awesome. You'll be amazed at how much the power valve can change the bikes power to exactly how you want it. Just remember, even quarter turns either way can drastically effect the way the power feels so its fun to go in or out quarter turns and spin a few laps. You'll know right away what feels best for you. The 49T rear really helps me carry more momentum into a corner in 3rd gear with just a tap of the clutch rather than have to constantly shift down to 2nd. 1.75-2 turns out helps 3rd gear smooth out a lot with the hit so you can pull it smoothly especially when approaching booters coming out of corners. Good luck!
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BR8ES
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BR8ES 5/13/2019 11:58am
5/13/2019 11:58am
CarlinoJoeVideo wrote:
I might try the 49 now. Hahaha! PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out. I...
I might try the 49 now. Hahaha!

PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out.

I agree with Ian, at that 1.75 (turns in) its very ridable.
BR8ES wrote:
Thanks for the PV info, gonna try that this weekend!
IanMac138 wrote:
Awesome. You'll be amazed at how much the power valve can change the bikes power to exactly how you want it. Just remember, even quarter turns...
Awesome. You'll be amazed at how much the power valve can change the bikes power to exactly how you want it. Just remember, even quarter turns either way can drastically effect the way the power feels so its fun to go in or out quarter turns and spin a few laps. You'll know right away what feels best for you. The 49T rear really helps me carry more momentum into a corner in 3rd gear with just a tap of the clutch rather than have to constantly shift down to 2nd. 1.75-2 turns out helps 3rd gear smooth out a lot with the hit so you can pull it smoothly especially when approaching booters coming out of corners. Good luck!
Yep, 49t works very well. Appreciate the test riding and settings, will definitely report back. Testing new SC2 carb as well, should tie the potting and Vortex CDI together nicely.

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JB28
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JB28 5/13/2019 1:41pm
5/13/2019 1:41pm
BR8ES wrote:
PV set from where? Full out, flush with housing, etc?
Glad someone else runs a 49t besides me.
CarlinoJoeVideo wrote:
I might try the 49 now. Hahaha! PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out. I...
I might try the 49 now. Hahaha!

PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out.

I agree with Ian, at that 1.75 (turns in) its very ridable.
BR8ES wrote:
Thanks for the PV info, gonna try that this weekend!
( First off yes my chain is loose. It’s new and stretched now and I will adjust it) So this weekend I went back to the same place, Breezewood proving grounds,so I could get the best feel for the adjustments made. I did 49t sprocket, PV adjsted 1.5 turns in, and drilled airbox holes on the left side (pictured) and on the right side 3 more 7/8” holes behind the side plates and out of the way for water and dirt to come in from the rear wheel. Let me tell you that is a totally different bike to ride!! Night and day! Like I slapped it around a bit and woke her up. She is very easy to ride and power is there immediately, while also being able to make power for longer in each gear. It is snappier and just all around way more responsive and powerful. Thanks guys. Gonna make trading her in on a 250 a lot harder to do in a few months.

I also switched from regular motor oil (10-40 or whatever) to bell ray 80w-85 transmission oil. That in combination with moving the shifter down one position, completely eliminated the false neutrals that happened 3-5 times every ride day, mid moto. (They sucked)
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BR8ES
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BR8ES 5/13/2019 2:03pm
5/13/2019 2:03pm
CarlinoJoeVideo wrote:
I might try the 49 now. Hahaha! PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out. I...
I might try the 49 now. Hahaha!

PV is from full out. It stops when you turn counterclockwise so don’t worry about it falling out.

I agree with Ian, at that 1.75 (turns in) its very ridable.
BR8ES wrote:
Thanks for the PV info, gonna try that this weekend!
JB28 wrote:
( First off yes my chain is loose. It’s new and stretched now and I will adjust it) So this weekend I went back to the...
( First off yes my chain is loose. It’s new and stretched now and I will adjust it) So this weekend I went back to the same place, Breezewood proving grounds,so I could get the best feel for the adjustments made. I did 49t sprocket, PV adjsted 1.5 turns in, and drilled airbox holes on the left side (pictured) and on the right side 3 more 7/8” holes behind the side plates and out of the way for water and dirt to come in from the rear wheel. Let me tell you that is a totally different bike to ride!! Night and day! Like I slapped it around a bit and woke her up. She is very easy to ride and power is there immediately, while also being able to make power for longer in each gear. It is snappier and just all around way more responsive and powerful. Thanks guys. Gonna make trading her in on a 250 a lot harder to do in a few months.

I also switched from regular motor oil (10-40 or whatever) to bell ray 80w-85 transmission oil. That in combination with moving the shifter down one position, completely eliminated the false neutrals that happened 3-5 times every ride day, mid moto. (They sucked)
Good feedback! I ran ATF this past weekend, shifted great, but could not find neutral while it was running 5o save my life. Looking forward to putting more time on my 125 after reading what you guys have done!

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