2017 Kawasaki Z125 Pro Yoshimura RS-2 Exhaust Install With Dyno Video

Kawasaki’s adorable Z125 sounds like a sewing machine in stock form, so we slapped on one of Yoshimura’s new RS-2 Mini exhausts. In this vid we go through the installation, flog the bike on the dyno, and let you hear what it sounds like.
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If you've watched this walkaround video of the Kawasaki Z125 Pro, you know that the Z sounds like a sewing machine. It's so quiet! And while we like the look of the under-engine exhaust, there's surely room for improvement. Lucky for us (and all the actual Z125 Pro owners out there) Yoshimura recently released its RS-2 Mini exhaust system for the 2017 Kawasaki Z125 Pro (click here to see our First Ride review).
First up, some background. The Yoshimura RS-2 Mini is mandrel-bent from brushed stainless-steel tubing and has a carbon-fiber-clad muffler. It's a beautifully crafted piece and sells for $499. For that stack of cash Yoshimura says your Z will lose 3 pounds and get a 5 percent boost in peak horsepower. Well we've got tools, a scale, and a dyno, so we decided to bolt the thing up and see what it's like.
The installation was pretty easy and took all of 30 minutes. The hardest part was mounting the Yosh muffler bracket. It bolts to the right-side passenger footpeg assembly (instead of to the underside of the swingarm pivot as on the stock system) via two U-clamps, and getting the hardware installed takes some dexterity and patience.
On our scale the stock pipe weighed 8.4 pounds. By comparison, the Yoshimura system weighed just 5.3 pounds. That’s a 3-pound savings, just like Yosh claims. On the dyno the bike’s peak output jumped from a pavement-rippling 8.69 horsepower to 9.14. That’s an increase of 0.45 horsepower, which doesn’t sound like much, but equates to a hair over a 5 percent increase. If your 100-horsepower bike gained 5 horses with a 30-minute bolt-on (and no fueling changes), you’d be pretty stoked, right? Besides bumping peak figures, the RS-2 adds thrust across the rev range.
Now the sound. The RS-2 is LOUD. It sounds decent at idle and partial throttle, but when you get on it (and let’s admit it, the Z is going to spend a lot of time wide open) the pipe is obnoxiously loud. Even with the included quiet tip installed, your neighbors will still hate you. I guess that’s one of the reasons this is a race-only exhaust!
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[@sachinmb6479]

Probably only people to do a dyno video of Z125 on KZbin... Cool

[@YoshimuraUSA]

That pipe is beautiful!

[@R1Anto]

His reaction for both pulls on the dyno really gave me a chuckle. Been in hospital for 4 days now. I needed that chuckle. 😀😀😀

[@gbner9991]

Im liking this channel more, good job guys!!

[@stevemack389sm]

I love the sound!!!!

[@keysandcarbs3654]

love the channel! keep them coming!

[@MackGully]

I finally found your new channel. Jesus christ I've been looking for it ever since you guys left Motortrend. You should really hire a digital marketer or if you have one they're not doing very well.

[@MackGully]

It's good to be back!

[@evan002]

What does a stock Grom dyno at? Have you guys put a Grom on the dyno yet? If not that would be really interesting to see.

[@czierwo]

I love mine. Bone stock. Over 6k this season only :D

[@jonsjs1]

Motorcyclist Magazine: did you get a check engine light on & stayed on after the exhaust install? If so, how did you get rid of it?I installed the same exhaust on my z125 pro but my check engine light stays lit. I double checked my installation, checked and re-checked the o2 sensor and connections but no luck. I even took out the o2 sensor and re-installed it, rode the bike for some time but the check engine light is still on. Disconnected the negative cable from the negative terminal of the battery for a few minutes and still no luck. Any ideas? As much as possible I don't want to take it to a Kawasaki dealer yet as they may charge me for diagnosis. Your feedback is appreciated.

[@pokefiendc3405]

do you have any maps you can sell for intake and exhaust

[@SestoElomenTo11]

good for pudding around on track days..or beginners confidence.

[@MJT-DA]

People don't realize that these 125cc bike weight a fraction of what a full size bike is. Firstly you don't need alot of power and they can do things that other bikes can't (off roading, skate park, elevator, tight spots, bicycle trails and much more!). These bike don't seem like much but they are going to be fun to customize and mess around on! XD

[@Astrothunderkat]

Not true, only 90 lbs lighter than a z500

[@MJT-DA]

@@Astrothunderkat still significantly smaller than the z500 so you can do more things with it.

[@Astrothunderkat]

@@MJT-DA yes, thats why i'll have both soon

[@MJT-DA]

@@Astrothunderkat lucky you only had enough for an older 600cc I wanted the z125 to just do dumb things on while saving fuel.

[@StrainXv]

and did you guys do the fuel adjustment?

[@markynzon]

Sir good day! Can i ask? Is it possible or is it okay to replace the centrifugal clutch assembly to a primary drive gear but still in an automatic clutch? In z125/klx110. Thank you.

[@dariohernandez1989]

Do a video for the grom with the same exhaust upgrade.

[@okoklorokoklor144]

yoshimura 14120AB250？or yoshimura 14120AB251 ?

[@Doogerauoy]

The Yoshi system looks and sounds great on the z125, but then you have to add a fuel module and things gets expensive. :)

[@adambomb9452]

o2 bung on the pipe?

[@diopork3904]

So Yoshimura wasn't lying on their page when they listed the horsepower gains as 4.9% increase to peak horsepower. 8.69 to 9.14 that's exactly 4.9%. I wonder if Akropovic routinely yields better improvements.

[@TerribleTimes]

That Yoshi didn't come with a DB killer...?

[@hommebizzare]

Why does the pipe coil around under the belly? I don't know anything about exhaust technology, but i can't see the benefit of having a longer pipe?

[@BambiOnDayZ]

The engine needs a certain amount of back pressure. If it just went straight out it would probably be too short and not create enough.

[@hommebizzare]

I have heard that before, but tests like this: /watch?v=_PVXvHkr-Vs seem to show that you don't need back pressure at all. As far as i remember, they had a small change in air/fuel mixture due to the increased air flow, but with electrically controlled injectors, i can't see why that would be a problem with the Z125

[@frosty-dogs]

Even with EFI there is not enough "trim" to compensate for having "no" back pressure. EFI systems have a very limited amount of correction values to compensate for atmospheric changes and load demands placed upon it by the rider. Not only that, but having "no" back pressure with today's fuel available at the pump would promote poor combustion or worse, detonation. Motorbike engines don't last too long under those conditions. An exhaust system is an integral component of the internal combustion engine.

[@hommebizzare]

Haha :) Okay, i won't discuss this anymore then

[@nicktimar3037]

I believe with a longer pipe it gives more back pressure to the engine which gives it a little more torque and a hair more top end speed.

[@nicktimar3037]

Why do I feel that there is no exhaust packing in the Yoshi?!?!?!

[@BruceMoolee]

is it true that with engine this small, there's no need to mess with the ECU if you put full exhausts on it?

[@CactusJack252]

MagickMaxX full exhaust you should. Just muffler you don’t. Because of the EPA you should anyways

[@joshuaalonzo8777]

Good video when are you going to review the z650 kawasaki

[@MotorcyclistMag]

This week! The press launch is this Thursday, so look for a First Ride report at Motorcyclistonline.com on Friday.

[@Deyquil_]

@motorcyclist magazine was that tuned?

[@Deyquil_]

Thanks for the quick reply. I think it's time to throw a Dynojet Power Vision on that bad boy!!

[@stevemack389sm]

but I WAS hoping for some more reasonable gain in power what else can be done to get more HP out of these bikes???

[@stevemack389sm]

***** thanks for the info THAT is something that I'll be watching for!!!!

[@ElDeLa883Iron]

nice

[@marurider69]

kawakhana : the Z escape ? no..ok 😭😭😂

[@sscarcello]

That's a bad little green bike. Have you seen the Honda Grom Scrambler Concept? Particularly the Gray one. Man, this bike will sell like mad. Ari, I am in San Pedro, can you guys DDyno my bike for a standard fee?

[@RobertKwolek]

That's at least 1 hp down from the Grom isn't it?

[@RedseTGaming]

nop, stock grom 8bhp

[@MJT-DA]

+Martin S grom makes 8.96 this z125 makes 8.69.

[@vstev3472]

sounds a LOT BETTER than the crappy Yoshimura wannabes fart cannon here (hell, they even just costs $199 for the ninja 300 and $99 for this bike)

[@Knivee1441]

Can it be installed on ninja 250 2010? reply please

[@sscarcello]

Google "Honda Grom 50 Scrambler Concept"

[@stenic2]

Mean

[@keabetsoe1998]

We miss the dreadlocks

[@Matttchew5]

go cart on two wheels

[@GIGABACHI]

All Single/Mono cylinder bikes are pretty loud, even when equipped with the OEM muffler...i personally don't like the sound.

[@mr.z5546]

$500 I can get that

[@RastaRider]

Incredibly small numbers hahahaha

[@A7XBilly]

benelli tornado 125 is waaay better!

[@tron121]

The can cost more than 5% of the bike

[@FPSdaybreaK]

paid 1300 for my bike. and it's getting a Yoshi rs3 cut in half.

[@broody2801]

j

[@rigging1377]

500 dollar pipe for a 3 grand bike lol

[@painville]

waaaay over priced.... and that noise is irritating!

[@TheHellokitty71]

boi

[@MrKitty-zv3dl]

$3,000.00 for a mini bike and $500.00 for an exhaust to make 1/2 HP? Where does the insanity end? Save your money... You'd be better off buying a used full sized road bike for $3,500.00.

[@FP541]

It only makes sense in europe where with the basic driving license (for cars) you can only drive 125cc bikes

[@mfbgaminghd2276]

Why would someone race than thing

[@ilovelimpfries]

cool bike, but $500 for a fart can!!? pass.

[@jivert1258]

Lol

[@d-nice2866]

They have cheaper ones

[@jaiburlingham2615]

Bike itself is only $3300, not spending 500 on the exhaust

[@ModDangFc]

$500? I'll stick with the stock exhausts.

[@CitizenJournoTN]

Not worth $500, wth? Maybe exhaust, and an air filter as far as power gains. I say get a slip on save the money and still get the sound. Take the leftover money and get an aftermarket air filter.

[@StrainXv]

Kinda hard to mount a slip on.

[@ele_motovlogs5798]

I do not have a grom or a z125 but I would rather have a grom because parts are less and there are alot of groms out there .

[@DaBrute]

Jesus $500!? I can get a twin exhaust catback for a car at that price

[@spiritbuu]

So basically a useless mod.

[@TheKamar2]

Do not buy 125cc bike just get a bicycle.

[@johnathanyinger]

What a waste of money! For $1400 more, you can buy a cbr300r instead of this hunk of garbage.

[@KonorSacks]

that is not the point

[@johnathanyinger]

Konor Sacks I know, but a scooter would be more functional. Or even an old 2 stroke enduro for a 1/3 of the price.

[@KonorSacks]

+Johnathan Yinger I guess it is more of a fun, not a practical thing...more of a social thing?

[@MadnessOfMarmots]

You're missing the entire point of these bikes.

[@KonorSacks]

+thinkpol me?