Must have YZ125 Mods and Common Issues

sdhuskyrider
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sdhuskyrider
Picking up a new 2020 YZ125 from Langston Motorsports tomorrow. What are some must have mods and common issues to be addressed on these bikes? I'm 5'11", 200 lbs (currently) so I am thinking about changing the shock and fork springs BUT I'm slow too so maybe not? At some point I plan to install a complete HGS exhaust system but beyond that I don't think I'll mess with it.
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FGR01
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FGR01 10/5/2019 9:39am
10/5/2019 9:39am
Yeah, stiffer springs should be the first thing. The forks will be riding too low in the stroke at your weight and you'll be forced to jack too much preload into the shock to get correct sag which will throw off the balance and handling even worse.

The stock jetting is pretty good if you run 32:1. If you run less oil like 40:1 or 50:1 it will richen the jetting and you might need to lean the jetting accordingly.
sdhuskyrider
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sdhuskyrider 10/5/2019 7:25pm
10/5/2019 7:25pm
Rode it today for a few minutes. I can tell its going to be perfect once I get adjustable top clamp on. Awesome bike!
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sdhuskyrider
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sdhuskyrider 10/7/2019 8:06am
10/7/2019 8:06am
Nial_Darragh wrote:
Long rod , vhm piston 12* best up grade wit
I have in stock
Email - nialdarragh176@gmail.com
Thanks I'll keep it it mind but I'm pretty happy with it power wise. Slapping a 49T sprocket on it and an adjustable top clamp for now.
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Schlava
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Schlava 10/7/2019 8:07am
10/7/2019 8:07am
sdhuskyrider wrote:
Rode it today for a few minutes. I can tell its going to be perfect once I get adjustable top clamp on. Awesome bike!
I feel the same way switching be between my 250f and my 125. Does anyone know if the 250f clamp is a direct swap?
Luxon MX
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Luxon MX 10/7/2019 10:04am
10/7/2019 10:04am
sdhuskyrider wrote:
Rode it today for a few minutes. I can tell its going to be perfect once I get adjustable top clamp on. Awesome bike!
Schlava wrote:
I feel the same way switching be between my 250f and my 125. Does anyone know if the 250f clamp is a direct swap?
It is not. Yamaha insists on making everyone's lives difficult and all the bikes have a different clamp setup. More specifically, the 250F top clamp has a 2mm smaller diameter fork tube clamp area and the bottom clamp has a different length steering stem compared to the two strokes.
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blaze 57
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blaze 57 10/7/2019 11:39am
10/7/2019 11:39am
sdhuskyrider wrote:
Who makes an affordable top clamp?
Yeah this ^ I would like to know too and what kind of difference it makes.
Moto Mofo
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Moto Mofo 10/7/2019 1:00pm
10/7/2019 1:00pm
Nial_Darragh wrote:
Long rod , vhm piston 12* best up grade wit
I have in stock
Email - nialdarragh176@gmail.com
How would you describe the change in power with this setup? I’ve seen these kits for sale, but haven’t found any real firsthand info in regards what it offers.
gristle568
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gristle568 11/5/2019 6:47pm
11/5/2019 6:47pm
I ran the 4 stroke triple clamps on one of my old yz 250s, just had a machinist buddy bore the top clamp 2mm and switched the stems. Depending on what year you use the offset is different.
Falcon
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Falcon 11/6/2019 10:38am
11/6/2019 10:38am Edited Date/Time 11/6/2019 10:38am
I had a braided steel brake line and an oversize rotor on a few of my YZ125s from back in the day. I could out-stop ANYONE. Your bike has a better master cylinder and a bigger rotor than my stock bikes did, but the steel brake line might be a good option for you.
X2 on the suspension; you may want to go with heavier springs.
KVA_536
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KVA_536 11/6/2019 12:54pm
11/6/2019 12:54pm
BUD Racing/HGS Pipe and Silencer
BUD Head
BUD Piston
Vortex IGN

Did this set up on my '06 build and its THEE best setup I've tested between all the popular brands.
Tracktor
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Tracktor 11/6/2019 2:25pm
11/6/2019 2:25pm
If you want real obvious power curve gains without any special fuel or reliability issues-

38mm Keihin Airstryker carb
STIC Metering Block

This will blow your mind. I have tested a stock bike with STIC against a full blown $3k mod engine bike. No comparison. Bolt on and enjoy 250f like power........
sdhuskyrider
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sdhuskyrider 11/6/2019 2:28pm
11/6/2019 2:28pm
Tracktor wrote:
If you want real obvious power curve gains without any special fuel or reliability issues- 38mm Keihin Airstryker carb STIC Metering Block This will blow your...
If you want real obvious power curve gains without any special fuel or reliability issues-

38mm Keihin Airstryker carb
STIC Metering Block

This will blow your mind. I have tested a stock bike with STIC against a full blown $3k mod engine bike. No comparison. Bolt on and enjoy 250f like power........
But how well was the TMX 38 dialed before that comparison? Everyone hates on the TMX but I have found that it makes better power than anything as long as you out the time into it. My TC250 went from brutally hard to ride to brutally fast and manageable once the TMX was dialed in.
AJ565
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AJ565 11/6/2019 3:07pm
11/6/2019 3:07pm
Tracktor wrote:
If you want real obvious power curve gains without any special fuel or reliability issues- 38mm Keihin Airstryker carb STIC Metering Block This will blow your...
If you want real obvious power curve gains without any special fuel or reliability issues-

38mm Keihin Airstryker carb
STIC Metering Block

This will blow your mind. I have tested a stock bike with STIC against a full blown $3k mod engine bike. No comparison. Bolt on and enjoy 250f like power........
sdhuskyrider wrote:
But how well was the TMX 38 dialed before that comparison? Everyone hates on the TMX but I have found that it makes better power than...
But how well was the TMX 38 dialed before that comparison? Everyone hates on the TMX but I have found that it makes better power than anything as long as you out the time into it. My TC250 went from brutally hard to ride to brutally fast and manageable once the TMX was dialed in.
I think the key is knowing how to tune the TMX. Most people give up when the main jet and needle clip change doesn't fix their problem.
Tracktor
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Tracktor 11/6/2019 3:27pm
11/6/2019 3:27pm
Tracktor wrote:
If you want real obvious power curve gains without any special fuel or reliability issues- 38mm Keihin Airstryker carb STIC Metering Block This will blow your...
If you want real obvious power curve gains without any special fuel or reliability issues-

38mm Keihin Airstryker carb
STIC Metering Block

This will blow your mind. I have tested a stock bike with STIC against a full blown $3k mod engine bike. No comparison. Bolt on and enjoy 250f like power........
sdhuskyrider wrote:
But how well was the TMX 38 dialed before that comparison? Everyone hates on the TMX but I have found that it makes better power than...
But how well was the TMX 38 dialed before that comparison? Everyone hates on the TMX but I have found that it makes better power than anything as long as you out the time into it. My TC250 went from brutally hard to ride to brutally fast and manageable once the TMX was dialed in.
AJ565 wrote:
I think the key is knowing how to tune the TMX. Most people give up when the main jet and needle clip change doesn't fix their...
I think the key is knowing how to tune the TMX. Most people give up when the main jet and needle clip change doesn't fix their problem.
Nope. I know how to tune carbs. Their isn't even a close comparison. I have 3 TC125's in my garage all with different setups at one time or another. The difference wasn't adding the Keihin it was adding the STIC metering block. It's ok, most don't believe it until they ride one. My oldest went from wanting to sell his 250f and get a 450 to only wanting to ride the 125. It's not a "tuning" difference it's a massive change in overall power and especially power delivery.......I have them on three bikes now and everyone who rides them is amazed. My 96 CR125 barely sat last weekend as kids were damn near fighting over it..........
1
Uncle Tony
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Uncle Tony 11/6/2019 6:12pm
11/6/2019 6:12pm
Tracktor wrote:
If you want real obvious power curve gains without any special fuel or reliability issues- 38mm Keihin Airstryker carb STIC Metering Block This will blow your...
If you want real obvious power curve gains without any special fuel or reliability issues-

38mm Keihin Airstryker carb
STIC Metering Block

This will blow your mind. I have tested a stock bike with STIC against a full blown $3k mod engine bike. No comparison. Bolt on and enjoy 250f like power........
What is STIC?

Pit Row

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AJ565
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AJ565 11/6/2019 6:50pm
11/6/2019 6:50pm
sdhuskyrider wrote:
But how well was the TMX 38 dialed before that comparison? Everyone hates on the TMX but I have found that it makes better power than...
But how well was the TMX 38 dialed before that comparison? Everyone hates on the TMX but I have found that it makes better power than anything as long as you out the time into it. My TC250 went from brutally hard to ride to brutally fast and manageable once the TMX was dialed in.
AJ565 wrote:
I think the key is knowing how to tune the TMX. Most people give up when the main jet and needle clip change doesn't fix their...
I think the key is knowing how to tune the TMX. Most people give up when the main jet and needle clip change doesn't fix their problem.
Tracktor wrote:
Nope. I know how to tune carbs. Their isn't even a close comparison. I have 3 TC125's in my garage all with different setups at one...
Nope. I know how to tune carbs. Their isn't even a close comparison. I have 3 TC125's in my garage all with different setups at one time or another. The difference wasn't adding the Keihin it was adding the STIC metering block. It's ok, most don't believe it until they ride one. My oldest went from wanting to sell his 250f and get a 450 to only wanting to ride the 125. It's not a "tuning" difference it's a massive change in overall power and especially power delivery.......I have them on three bikes now and everyone who rides them is amazed. My 96 CR125 barely sat last weekend as kids were damn near fighting over it..........
Should be easy to test back to back with a LITPro. Maybe one of these days I’ll buy one to try, but car parts are a little more important to me right now lol. My shifter kart uses a ‘96 CR125 engine because that was the best year of them. That would also be a good back to back that I’d like to try too.
Tracktor
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Tracktor 11/7/2019 9:25am
11/7/2019 9:25am
Tracktor wrote:
If you want real obvious power curve gains without any special fuel or reliability issues- 38mm Keihin Airstryker carb STIC Metering Block This will blow your...
If you want real obvious power curve gains without any special fuel or reliability issues-

38mm Keihin Airstryker carb
STIC Metering Block

This will blow your mind. I have tested a stock bike with STIC against a full blown $3k mod engine bike. No comparison. Bolt on and enjoy 250f like power........
Uncle Tony wrote:
What is STIC?
Upated metering block for Keihin Airstryker carbs. It completely changes the way the carb atomizes fuel and does amazing things to the power delivery- Developed by George Boswell.

http://www.sticsupertorque.com/

It's tough to make people believe util you have tried one. We have done a bunch of testing back to back plus did "blind" tests with my boys and every time they were blown away by what it did to the power curve of every 125 I put one on. I've had a few friends try them also with the same results.........
1
Moto520
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Moto520 11/7/2019 9:37am
11/7/2019 9:37am Edited Date/Time 11/7/2019 9:39am
1) go up one tooth on the sprocket
2) go one size fatter on the main
3) Moto Tasinari V-force reeds
4) FMF or Pro Circuit pipe and silencer
5) after riding stock...decide if you want to go stiffer on the suspension. i'm 190lbs and i just ride it with the stock soft shit since it's not my race bike. Soft but good enough

none of these changes are critical except maybe going a little fatter on the main....
yz133rider
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yz133rider 11/7/2019 1:52pm
11/7/2019 1:52pm
Moto520 wrote:
1) go up one tooth on the sprocket 2) go one size fatter on the main 3) Moto Tasinari V-force reeds 4) FMF or Pro Circuit...
1) go up one tooth on the sprocket
2) go one size fatter on the main
3) Moto Tasinari V-force reeds
4) FMF or Pro Circuit pipe and silencer
5) after riding stock...decide if you want to go stiffer on the suspension. i'm 190lbs and i just ride it with the stock soft shit since it's not my race bike. Soft but good enough

none of these changes are critical except maybe going a little fatter on the main....
#4 is kinda a waste of money on the pipe. Look at dynos and while they might gain a tiny bit at peak they fall off hard compared to the stock pipe after peak reducing the usable range.

A shorty silencer is a good move. But for the price of an exhaust and silencer id suggest having it ported 10/10 times. Same price and actually legitamate gains not a tenth of a hp, taking several horsepower gains with porting.

Moto520
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Moto520 11/7/2019 7:57pm
11/7/2019 7:57pm
yz133rider wrote:
#4 is kinda a waste of money on the pipe. Look at dynos and while they might gain a tiny bit at peak they fall off...
#4 is kinda a waste of money on the pipe. Look at dynos and while they might gain a tiny bit at peak they fall off hard compared to the stock pipe after peak reducing the usable range.

A shorty silencer is a good move. But for the price of an exhaust and silencer id suggest having it ported 10/10 times. Same price and actually legitamate gains not a tenth of a hp, taking several horsepower gains with porting.

i totally agree. A pipe does very little. Dont waste the money
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FGR01
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FGR01 11/11/2019 8:55am
11/11/2019 8:55am
I’ve just about every pipe and silencer on the YZ125. I’ve found the shorty to not be so good. You lose a bunch of overrev. I prefer mid-length like the normal FMF. Right now I’m running the Bill’s carbon silencer and Bill’s pipe. Very nice combo.
sdhuskyrider
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sdhuskyrider 11/11/2019 8:58am
11/11/2019 8:58am
FGR01 wrote:
I’ve just about every pipe and silencer on the YZ125. I’ve found the shorty to not be so good. You lose a bunch of overrev. I...
I’ve just about every pipe and silencer on the YZ125. I’ve found the shorty to not be so good. You lose a bunch of overrev. I prefer mid-length like the normal FMF. Right now I’m running the Bill’s carbon silencer and Bill’s pipe. Very nice combo.
Same accept I went with the aluminum silencer. It definitely woke the bike up a bit.
sdhuskyrider
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sdhuskyrider 11/17/2019 1:34pm
11/17/2019 1:34pm
For anyone following the thread and wanting to know about these mods:

49T Sprocket- Big bang for the buck. Makes the bike feel a bit more torquey and helps the rider stay on the pipe.

Bill's Pipes Expansion Chamber and MX2 silencer - I didn't feel a loss of low end but I do feel a little bit more in the middle and even more so up top. The bikes sounds MUCH better and I haven't even sorted the jetting out yet. I'm really happy with the purchase and it's really going to shine with proper jetting. The stock global spec is crap.

Race Tech Fork and Shock Springs - Getting the bike sprung for my fat azz was huge for how the bike handled. I feel much more confident now. I didn't alter the oil volume or clicker settings from stock. Feels awesome as is. It only took me a few hours to swap the springs and they cost about $275 with shipping and tax. A must do.

Next step is getting the head cut to run 50/50 fuel and getting the jetting sorted out. This YZ125 kicks azz. Best bike I've ever owned.
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Uncle Tony
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Uncle Tony 11/17/2019 1:44pm
11/17/2019 1:44pm
The yz125 is a great machine, I love mine, if I had a complaint it’s keeping clutches in it, I drill the hub (boss as Yamaha calls it) and replace the hub and pressure plate whenever I do a clutch, only get about 10 to 15 hours

I girl that I race with gets even worse, probably 6 to 8 hours, she known as captain clutch

I’m probably going full Hinson next season, any suggestions on oil? I use Motul trans oil
1
sdhuskyrider
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sdhuskyrider 11/17/2019 2:40pm
11/17/2019 2:40pm Edited Date/Time 11/17/2019 2:40pm
Uncle Tony wrote:
The yz125 is a great machine, I love mine, if I had a complaint it’s keeping clutches in it, I drill the hub (boss as Yamaha...
The yz125 is a great machine, I love mine, if I had a complaint it’s keeping clutches in it, I drill the hub (boss as Yamaha calls it) and replace the hub and pressure plate whenever I do a clutch, only get about 10 to 15 hours

I girl that I race with gets even worse, probably 6 to 8 hours, she known as captain clutch

I’m probably going full Hinson next season, any suggestions on oil? I use Motul trans oil
I would stop using the clutch. I only use mine when I want to shift up WFO and not let off the throttle.
Uncle Tony
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Uncle Tony 11/17/2019 3:02pm
11/17/2019 3:02pm
sdhuskyrider wrote:
I would stop using the clutch. I only use mine when I want to shift up WFO and not let off the throttle.
I’m riding Tuesday I will try, I ride a lot of sand and like to keep it a gear up

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