Kawasaki Z125 Forum banner

1 - 20 of 125 Posts

·
Registered
Joined
·
557 Posts
Discussion Starter #1 (Edited)
Write-up, July 2020 updated

Well, picked up a little something to ride around town and the kart track. It started out green but I swapped out to my normal race colors.

25332


As part of this update, here and there I may provide links to discussions about build options.

Some background. I've been exclusive to big race tracks and fast bikes for about 5 years. It's been fun, but it's been expensive as ****, with race tires, fixing crashed bikes and medical bills. Since 2014 I broke 11 bones and have 3 titanium plates with 50 screws. I've crashed at the kart track 3 times and the worst I ever got was a slightly sprained thumb. (Remember to make a fist when you fly like superman off a high side) But anyway, some other medical issues are forcing me out of the big track and back to the little track. I rode supermoto bikes there maybe 6-7 years ago and I missed it.

This bike is a track tool only. Though I am still keeping it street legal for various services, like pit bike duty and running to the YMCA to work out, etc. In this build, price is important. My last race bike, a Ninja 300, I ended up dropping $10K into. I don't want to do that again, especially on a 125. This is really a budget build.

I picked the Z125 over the Grom for a couple primary reasons - way better suspension from the factory, more lean angle with the pegs 2" higher, and it just looks better. Picked it up for $2626 at Southeast Sales (Milwaukee) during a sale they had with no additional fees beyond TTL. OTD for a few bucks less than $3K. Good timing, the 2018's go up to $3200 or $3400 if you want the "special" paint job with the bold new graphics. (no thanks) Ok on to the mods:

Yoshimura RS-2 Full Exhaust & Bazzaz Z-Fi - The Bazzaz was a much better value. I have some good options for dyno tuned maps to load up in the Bazzaz. I am accepting the Bazzaz over a Power Commander only because I don't have a plan to run race fuel. The Bazzaz does not allow for ignition adjustments like a power commander. Running race fuel? Don't get the Bazzaz. There are lots of exhaust options for this bike so far, but the Yosh is one of the better horsepower options. The Comp Werkes system looks nice with the way it tucks under the bike, but I believe the exhaust is so short that midrange power would suffer. The Yosh curls around and makes a loop under the bike for a longer effective length. Ordered by calling Riders Discount directly, which is their business model - their price on both items was WAY lower than anyone else. RD Is the bane of other vendors. I save well over 3 digits on these items buying from them. Make sure you have your rear preload cranked up or the Yosh will drag during hard cornering.

Chimera Z125 Short Stack Ram Air Intake - Chosen mainly because it has a crankcase breather connection. Ordered from HardRacing.

PMT Soft Race Tires - No questions, the best track tires you can get, and don't fall for anyone trying to tell you anything different. Mitas are almost as good. The next level are the street based DOT race tires like the Kenda KD1 or Dunlop TT93. I ran the TT93's before. They are decent and will last a long time. The main concern with PMT softs for me was tire life. Some people would say you get 2 days out of them. It depends on where you run them. If you run on rough crappy asphalt in a desert climate, yes, 2 days. Run on quality asphalt in Wisconsin like me, I get 6-8 days. I buy PMT from Minimob in Canada.

Woodcraft front and rear axle sliders - Decent sliding protection for the axles, at least the fronts, and the non-exhaust side rear. Many tracks require some axle protection. Both of the track I got to do, and you can't blame them - their asphalt is perfect.

Motodynamic tail light - Purchased directly from Motodynamic in case I need to exercise the warranty rights. This bike might spend a bit of time on the street, and I don't want the heavy beaver tail (4.5 lbs), so I had to have this. The price was decent and I liked the look of it more than the TST or Mnnthbx options. As a bonus, it appears to have all the correct plugs, so no wire stripping is required. Has a load resistor too. I installed it right away to rid the bike of that massive beaver tail. I have one or two license plate brackets laying around that I can use. Easy installation. I believe this is the best integrated option out there. Update: 3 years later, same tail light, no issues.

Gcraft Shift Shaft Guide - VERY important modification, with the DIY linkage below. Purchased from Webike in Japan because the majority of vendors in the states are just not with the program. The Z125 has sloppy notchy shifting for several reasons. This resolves one major reason - the shift shaft extends too far out and under load it flexes. [link] Very hard to get and rarely in stock. Was once in stock at Steady Garage 3 years ago and never restocked, and their "Sign up to get notified when this product is back in stock" is seemingly some kind of sick joke. It IS restocked occasionally at Webike Japan.

Custom shift linkage with McMaster parts - Another very important modification. [link] Dig into the OEM shift linkage and you will see some garbage that looks like it came off a lawn mower. A bent rod sticking through a hole? Really? No wonder it doesn't feel very good. This mod, along with being sure your motor frame bolts are fully tight improves shifting feel.
25336


EBC Contour Front Rotor EBC-1032 - The best rotor you can buy for the Z125 and it's not even that expensive. I first had a Galfer rotor and it was generally low quality and had some issues. It had grinding from poor grade machining and it had pulsing from machining errors. It took a bit to figure this out as it didn't show up in a runout test to check for warpage. But along the edge there was a small section on one side that was machined to a slightly deeper depth than the rest of the rotor so it never contacted the pad. Pulsing came from that. Grinding just came from rough machining all around. What utter garbage. Stay away and get the EBC. They never let me down. Note: I need to keep the front caliper, so no Brembo mods for me. There is a chance that I may someday race in a Grom/Z125 class with supersport rules that requires the OEM calipers.

Vesrah RJL Brake Pads (imported from Japan) - There are no good brake pads available for the OEM caliper, even 3 years later, in the United States. So I had to custom order Vesrah pads from Webike in Japan. They feel soooo good with the EBC rotor. Finally, good braking on the bike. Now, Webike Japan stocks them. [link] There are a few Vesrah options there now, but what you want are the model number ZV-SD186, and based on the SD in there and Vesrah's description in the street pad lineup, they appear the be RJL ceramic. With these there is an increase in initial bite, exactly what the OEM system needs.

Galfer SST Line, Front - While I didn't like the rotor, Galfer lines have never let me down. Front only, I'm not touching the rear brakes on this. I don't use the rear brake EVER unless I blow a turn and start off roading. To me, the Galfer kits available are somewhat wasted money with rear rotors, pads and stainless lines. Get just the line, and just the front. It's where you need the feel improvement. [link] Bought from Drow sports because they sell the front individually.

Bikers Front Fork Preload Adjusters - From Webike in Japan, lacking good options in the US at the time. There was some discussion on the forum if these actually do anything besides raise the front end. It felt like they helped, but I did these at the same time as the fork oil so I don't know. So then I did a test - I took a low range industrial crane scale with a winch strap and measured the force required to bottom the forks when the preload adjusters are up vs down. It does take more pounds to bottom the forks when the preload caps are cranked down, so they appear to be doing something. I consider these preload adjusters to be a cheap bottoming resistance tool. BTW, don't be afraid of Japan.webike.net, they aren't shipping garbage like Ebay, Amazon or AliExpress. [link] Price has doubled since I bought these... might as well just buy Takegawa sets in the states if you want preload adjusters. (and you think they work)

Bel-ray 15W fork oil - Important for OEM forks. Compression is a little weak in the OEM forks. Going up to 15W fork oil helps. There is some talk amongst track dudes that 20W works well too, or at least after the oil warms up. I might give that a try next. Note that this is a budget build and to keep the cost down I don't intend to do any suspension mods. I will run OEM suspension. So far, stock feels pretty good (ok I'll just say good enough) with 15W front fork oil, which was surprising for a bike at this price point. Strong springs too. The Grom felt mushy and sloppy in comparison. I think a lot of people don't realize that fork oil weight can be a significant adjustment.
Soap box speech time: One thing I'm tired of is vendors telling everyone that their big dollar suspension parts are "required" for your bike and they will "transform" the performance. Don't fall for it. You don't need to blow that much money. Geez, these few cheap parts in my list and I'm already past the +$2K mark. I don't need to double the cost of the bike. It's not going to make me any faster. All that's going to make me faster is skill, and I can't go to MNNTHBX, get out my credit card, click some buttons and get it sent to me in a box. There's nothing wrong with buying suspension parts for your bike, or $5K worth of other parts for that matter. Just recognize that you buy it to make yourself feel good and you generally don't need it.
Billet annodized brake and clutch Levers - I picked up a set of cheap chinese levers off ebay because I feel like I need the adjustability. DON'T buy cheap chinese levers, especially brake levers, unless you are willing and able to check fitup tolerances. These are hit and miss, and some people have crashed because of a brake lever that binds at the plunger pin. Then the rotors and pads heat up, brake fluid boils and expands and the front end locks up. I will check these prior to installing. If measurements don't fall within reasonable tolerance range of the originals, I throw them in the garbage and get a set of ASV levers.

Protaper SE Handlebar, Honda Mini bend - This is the 2nd set of bars I tried. I originally got the Schoolboy Low but they were too low and hit my legs in sharp turns. (I'm 5'-11") - This Honda Mini bend works well, fits me, and will go full lock to full lock with just enough upward rotation. I think one of the important things here is that the OEM bars are weak. The first time you go down, they are getting bent into an unusable shape. The Protapers are strong enough to survive a downer, and the position is more sporty and forward, which feels better for track riding. OEM is pure upright which feels awkward at the track.

T-Rex Racing Bar End sliders - Lacking handguards, I got bar end sliders. Note that bar end sliders that fit aluminum dirt bike style bars like Protaper are hard to find. They need a smaller 14mm insert. T-Rex is one of them. Look for the model advertised as fitting the KTM SMR 450. [link]

Ebay Adjustable footpegs (25mm rotating) - I call this the large foot mod. This type of footpeg can be rotated 360 degrees. All the way down for less knee bend, all the way up for way more cornering clearance. But I have them configured all the way back and up 5mm. What that does is gives my foot a little more shifting room, the bike a tiny bit more cornering clearance, and the position allows my knees to tuck into the gas tank better. Another benefit for the position I chose is that the bracket works as additional foot support. I had to grind the stops down a bit so the pegs would sit flatter.

The Ebay Auction is long gone but I'm sure there are still similar items out there. [link]
25337


Endplate swingarm spools (Area 22 clone) - There are a couple versions of this. You can get the Area 22 version for $70 [link], proper clones for $30 or less, or incorrect clones. Proper clones have a set screw top and bottom that holds the end plate in place once the rear axle is removed, but these are hard to find in the states because Area 22 stomps out counterfeits. They are all over AliExpress if you want to take the chance there. [link] The set screws are important or these are useless for changing rear tires. Incorrect clones don't have the set screws. Link provided for info - do not buy. [link] They will fall out as soon as you loosen the rear axle. Note: do not sit on the bike when up on rear stands with these swingarm spools. It applies excessive stress to the set screws that hold the end plates on and could loosen them.

Motul RBF600 brake fluid - total overkill for the bike. You can buy any cheap brake fluid. RBF600 is what I needed to keep my brakes from boiling when heading into turn 5 at Road America on a middleweight and I need to scrub 100 mph in 3 seconds.

TST Fender Eliminator - I think I had this laying around. Easily removed for track duty.

Carbon fiber license plate frame - Adds 5 HP! Ok, I had this laying around too.


Miscellaneous parts

Red plastics to replace green
- Surprisingly cheap at cheapcycleparts.com. Made cheaper when I dropped my green plastics on ebay after. I think my net expense was $100. Red and white have been my race colors for a decade. I only got green because it was discounted.

Z125 decals from seventysevendecals.com - OEM decals however are super stupid cost. When you buy new plastics they come without OEM decals. I went here to get them and they had some nice color options too. Looking at their web site, I don't think they sell these any more.
25338

My first set I got from them were rose gold, but ended up looking more metallic pink, so I then order normal gold. I still have the metalic pink decals. Would probably look good on a gray bike.

Custom cut white vinyl side trim
My old Zaph Racing decals and various others

Formed Aluminum Mobius Camera fork mount
- Needs work drilled mounting hole too big and the camera doesn't sit flat so it vibrates a bit.
25339


Mobius 2 action cam for video - just upgraded from my old Mobius original


Parts I got rid of

Kemimoto CNC Adjustable Rearsets
(not mounted - garbage) - Had a fun "discussion" with old forum blow-hard Jim G about these. [link]

Protaper SE Handlebar - Schoolboy Low bend (too low for my size) - Too low for my size but if you are 5'-6" or so, might work.

Moose Racing Aluminum handguards (did not fit) - Most normal dirtbike style handguards will not fit. If you want hand guards you need the "stubby" kind that bolt closer to the grip. Like the Acerbis Tri-Fit models. [link]
 

·
Vendor
Joined
·
681 Posts
Looks good. You should have hit us up on that braking package, as we're able to group it at a deeply cut price. Our ASV levers aren't even comparable to the import stuff if you decide you need them. Have fun on the track!
 

·
Registered
Joined
·
557 Posts
Discussion Starter #3
Let us know when the good pads are coming. I really want Vesrah RJL's for this. They worked so great on my Ninja 300 build with their crappy OEM caliper, and they are favorites with the SV650 racing crowd too, It's a pad that by design brings out the best of old caliper tech.
 

·
Registered
Joined
·
557 Posts
Discussion Starter #5
Yeah I got it a little cheaper than that.

I heard a rumor though that the Yosh RS2 might have a right side cornering clearance issue for serious racers. I have to look into it. The solution might just be to add some ride height or tweak the installation.

Mostly, I just have to start getting the rest of my parts bolted up, take a run at the track and see where things stand.
 

·
Vendor
Joined
·
681 Posts
Sintered pads are coming, but I'll say the Galfer organics we use are a solid improvement.
The Yosh could touch down right side, but honestly no more than any other system. It's tucked tight to the bike.
If you're pushing hard enough to be concerned with the pipe, upgrade the forks with the Ohlins inserts. Night and day from a performance standpoint. Faster lap times for sure, and it will keep the bike riding higher in the stroke, increasing ground clearance in the turns. We have a how-to video in our section.
Keep an eye out for for coming posts. We're currently building a turn-key track bike for corporate Kawasaki, and will document all of it.
 

·
Registered
Joined
·
315 Posts
Yeah I got it a little cheaper than that.

I heard a rumor though that the Yosh RS2 might have a right side cornering clearance issue for serious racers. I have to look into it. The solution might just be to add some ride height or tweak the installation.

Mostly, I just have to start getting the rest of my parts bolted up, take a run at the track and see where things stand.
That would suck if true. I haven't heard anything like that yet. Even if true I'm still getting the yosh. Haven't found another pipe with the loop besides the zoom.
 

·
Registered
Joined
·
557 Posts
Discussion Starter #8 (Edited)
Does anyone else think that many of the exhaust options are too short? I just think back at a little of my history of trying to get good power out of short exhausts and ending up with a gutless bike.

The Comp Werkes is highly crashable the way it's tucked under, but I would like to see a real dyno curve with it.

The Yosh on my 300 never came close to touching down. But that was like a 7/8 size bike while the baby Z is a 2/3 size bike. In any case, I bought it and I'll find out. Worst case I think it will be fine if I get new springs more suitable to my massive mass. (215 lbs) Probably going to need them in the front anyway. The rear seems stiff enough with full preload cranked up.

Maybe it just might be good enough to improve my body position a bit. I mean, Grom riders with stock footpegs practically have to sit on the sides of their bikes in turns, Lol.
 

·
Registered
Joined
·
64 Posts
Does anyone else think that many of the exhaust options are too short? I just think back at a little of my history of trying to get good power out of short exhausts and ending up with a gutless bike.

The Comp Werkes is highly crashable the way it's tucked under, but I would like to see a real dyno curve with it.

The Yosh on my 300 never came close to touching down. But that was like a 7/8 size bike while the baby Z is a 2/3 size bike. In any case, I bought it and I'll find out. Worst case I think it will be fine if I get new springs more suitable to my massive mass. (215 lbs) Probably going to need them in the front anyway. The rear seems stiff enough with full preload cranked up.

Maybe it just might be good enough to improve my body position a bit. I mean, Grom riders with stock footpegs practically have to sit on the sides of their bikes in turns, Lol.
You check out the Comp S from Two Bros? There was a guy selling those for like $300. Sits a little higher than the Yosh.
 

·
Registered
Joined
·
162 Posts
Well, I'm one of those who has dragged the Yoshimura pipe while track riding. I chose their pipe because of their excellent reputation and the design of the pipe shows a lot of thought went into it. But it's not perfect. It comes with the smaller 14mm bung for the OEM O2 sensor so an 18mm wideband sensor for the Autotune won't fit. Having to cut up a brand new pipe kinda sucks. Once installed everything fits well and it's a good looking pipe. But on the track the pipe will touch down just as you drag the stock pegs. On the street this will only be an issue on some very steep driveways but it's sold as a "race" exhaust and it's disappointing that it doesn't work for the track. When I called them about it they seemed surprised and sent out a replacement pipe section so their customer service is responsive. The R&D guys should have done just a little more testing.

After looking at other pipes I chose the TBR Comp exhaust since the ground clearance was better and it comes with an 18mm sensor bung installed. So far it has not touched down and there is no difference in the bike's performance on the track. It might be slightly shorter and heavier than the Yosh but it's just as loud. And it was $100 cheaper which is about what a 12" racing slick costs.
 

Attachments

·
Registered
Joined
·
64 Posts
Well, I'm one of those who has dragged the Yoshimura pipe while track riding. I chose their pipe because of their excellent reputation and the design of the pipe shows a lot of thought went into it. But it's not perfect. It comes with the smaller 14mm bung for the OEM O2 sensor so an 18mm wideband sensor for the Autotune won't fit. Having to cut up a brand new pipe kinda sucks. Once installed everything fits well and it's a good looking pipe. But on the track the pipe will touch down just as you drag the stock pegs. On the street this will only be an issue on some very steep driveways but it's sold as a "race" exhaust and it's disappointing that it doesn't work for the track. When I called them about it they seemed surprised and sent out a replacement pipe section so their customer service is responsive. The R&D guys should have done just a little more testing.

After looking at other pipes I chose the TBR Comp exhaust since the ground clearance was better and it comes with an 18mm sensor bung installed. So far it has not touched down and there is no difference in the bike's performance on the track. It might be slightly shorter and heavier than the Yosh but it's just as loud. And it was $100 cheaper which is about what a 12" racing slick costs.
Yep, and also you can grab a baffle for it if you choose to pop one in during street rides.
 

·
Registered
Joined
·
557 Posts
Discussion Starter #13
Thanks for the pic Lobot. Did you still have the feeler pegs on the footpegs? If you have them off, maybe leaving them on is a good warning that you're about to drag stuff.

I'll be taking several steps to ensure I have the most ride height I can get, along with tweaking the installation in a couple ways to get a little bit more clearance. I'll report back if I find a solution.
 

·
Registered
Joined
·
162 Posts
Yes, the stock feelers were on but since the pegs can pivot out of the way, eventually something else will touch down and it was the Yosh pipe. With the Two Bros pipe I was able to cut the feelers down in half so we get a bit more lean angle before they hit. This was while running Dunlop TT93 tires which have pretty good grip for the money. Since they are DOT rated they are a bit heavier and have slightly less grip than the PMT slicks we have now. We also have those preload adjusters up front with 20w fork oil so it doesn't dive under braking anymore. I think heavier springs might be a step better but they will upset the balance unless we pop for a better shock. That's not in the budget at the moment. Someday...
 

·
Registered
Joined
·
315 Posts
Well, I'm one of those who has dragged the Yoshimura pipe while track riding. I chose their pipe because of their excellent reputation and the design of the pipe shows a lot of thought went into it. But it's not perfect. It comes with the smaller 14mm bung for the OEM O2 sensor so an 18mm wideband sensor for the Autotune won't fit. Having to cut up a brand new pipe kinda sucks. Once installed everything fits well and it's a good looking pipe. But on the track the pipe will touch down just as you drag the stock pegs. On the street this will only be an issue on some very steep driveways but it's sold as a "race" exhaust and it's disappointing that it doesn't work for the track. When I called them about it they seemed surprised and sent out a replacement pipe section so their customer service is responsive. The R&D guys should have done just a little more testing.

After looking at other pipes I chose the TBR Comp exhaust since the ground clearance was better and it comes with an 18mm sensor bung installed. So far it has not touched down and there is no difference in the bike's performance on the track. It might be slightly shorter and heavier than the Yosh but it's just as loud. And it was $100 cheaper which is about what a 12" racing slick costs.
Stock tire size?
 

·
Registered
Joined
·
162 Posts
I think they were the 100/90-12 front and the slightly taller 120/80-12 rear Dunlop TT93s. They have decent grip and wear pretty well. Not the best track tire out there but a good compromise for the money. And they are street legal so they will do double duty unlike the racing slicks.
 

·
Registered
Joined
·
557 Posts
Discussion Starter #17
Lobot, we have a lot of questions for you. When you went to 20 w fork oil, did you notice any chatter in bumpy turns? Seems like an agressively heavy oil.

I'm just thinking of the last time I used 20 w fork oil, (different bike) it practically locked up the front suspension and I had to get it out right away. Maybe I'll start at 15 and see how that feels, unless you're super confident about that weight.
 

·
Registered
Joined
·
162 Posts
The front forks are pretty decent on the street but they dive under hard braking. The Service Manual says 10w oil is standard so I tried 15w which was better until it warmed up and then it's back to front end dive. I added some preload adjusters and that seemed to stiffen it a little but it still would dive more than I liked. Once I tried 20w oil it felt like the dive was under control even when hot but it never felt harsh to me. I have not upgraded the brakes yet as I'm waiting for better pads for the stock caliper. Better braking might require further work on the forks but I'm happy with them now.
 

·
Registered
Joined
·
557 Posts
Discussion Starter #20
Here's the brake upgrade for everyone until we get some good pads, hahah.



The preload adjusters I ordered from Japan at Webike came in only 3 days, WTF. Seriously, I ordered on the 7th. Shipping cost $17.50 not too bad for international air.
 
1 - 20 of 125 Posts
Top