2003 Yamaha YZ 125 Revival

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9/23/2018 10:59 AM
Edited Date/Time: 3/8/2019 5:27 PM

A few months ago I was lucky enough to score a semi-rebuilt 2003 Yamaha YZ125. The previous owner replaced most, if not all of the wear parts and even had the old parts for proof. In addition he added a rebuilt 1997 YZ125 motor, which he preferred for more torque. I gotta say this motor probably has the most torque of any 125 I've ever ridden. The bike supposedly has 20 hours since the previous owner freshened it up, which I believe is true. The powdercoated frame and swingarm only had one ride when I picked the bike up.

I'm currently in the process of finishing this build with the goal of creating a fast, reliable 125 that I can use to have have fun, race, and get more seat time.

Here is where the build started. A lot of nice aftermarket parts were previously installed that I plan to keep such as the Excel Takasago rims, a fresh set of Michelin Starcross tires, Pro Taper bars and clutch perch, and a few other minor pieces.Photo




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9/23/2018 11:47 AM
Edited Date/Time: 3/8/2019 5:31 PM

I had some spare time, so I decided to polish the FMF exhaust and silencer even though it will be replaced with a Pro Circuit system for more top end power.Photo

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I had ridden the bike once around our property to get a feel for it, and then raced it at MxExpress-Toledo's Two Stroke Shootout. I went into the day with little expectations as I had yet to ride it on a track, and I finished around 7th in my class. Not bad, but certainly room for improvement with both myself and the bike. The motor comes on strong off the bottom with lots of torque, but falls flat on top. Setup wise I could tell the balance and clickers were a bit off for my preferences, especially on a track that develops lots of chop and deep ruts. Still had a blast and can only imagine how much better I'll be able to ride once I more time to make adjustments.

After the Two Stroke Shootout I started with the first round of parts including a Boyesen ignition cover, Motoseat cover and foam, Cycra restyled plastics, Pro Taper grips, and carb vent hoses.

I also noticed a few scratches on the freshly powder coated frame so after researching the options for frame guards, Light Speed's carbon guards seemed like the way to go.

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9/23/2018 11:55 AM
Edited Date/Time: 3/8/2019 5:31 PM

After these pictures were taken, I rode our local practice track and the reeds gave out on me during the first moto. I took the bike to my mechanic for a fresh top end, V-Force reeds and a Pro Circuit exhaust. I'm lucky to have a local and very experienced mechanic who will get this bike running crisp and tuned to my liking.

I also have a carbon skid plate on order from Light Speed for added protection and durability.

I'm excited to see the improvements once I get the bike back. My plans going forth are to fine tune the suspension, install graphics, and let 'er rip! Hopefully I'll be healed up in time to ride before winter whistling

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3/8/2019 6:35 PM

Missed out on riding the bike before winter, so we're currently trying to get the bike finished up while the weather is still cold.

Upgraded the rear brake pedal to a Hammerhead Designs setup. I previously had a Hammerhead brake pedal tip when I had a KTM, and thought that it provided a better feeling than stock. Nice upgrade from a functionality and looks standpoint.

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One issue I wanted to get fixed during this build was the front brake line setup. The previous install looked sloppy, and I noticed that the line was rubbing on the rotor and it was only a matter of time before a failure happened.

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For whatever reason, the bike came with a 1997 YZ 125 front master cylinder installed, so we upgraded back to the 2003 OEM setup. The main reason being that it's much easier to adjust the front brake lever on the 03 and the fitment between the master cylinder and the throttle housing is improved.

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3/8/2019 6:53 PM

Headed back to the shop for the final pieces of the build. I never touched the clickers prior to riding the bike, and my mechanic discovered that the adjusters on the left fork don't engage. Going to have this fixed, and get the forks and shock rebuilt.

Also time to get the top end changed, some porting, and hopefully Pro Circuit and the distributors pull through with getting the pipe in. Been on back-order for 6+ months.

Here's a sneak peek of the graphics. My brother designs custom graphics, so he hooked me up with a clean design.
More of his work can be seen on Instagram: @dabaum_designs

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Some Vital members have probably seen his work on Zesiger 112's YZ 250. Zesiger 112 provided the design and he helped bring them to life.

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1/20/2020 8:45 AM
Edited Date/Time: 1/20/2020 8:49 AM

Little update on the YZ build. Since the last post, I've made quite a few changes.

Graphics installed and scored an FMF 2.1 Ti silencer.
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Turbo Speed Tuning rebuilt and revalved the suspension for my weight and fixed the clicker issue. Bike works so much better now. 🤘
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While the suspension was off, I greased all the bearings and surprisingly they looked like they were recently packed. Also replaced all of the OEM bolts that I removed during the process with Specbolt pieces.
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From here, finished the 2019 year off putting some time on it.
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This past month, GBR Performance did a complete rebuild on the motor. Fresh piston, Hinson clutch, rebuilt crank, and replaced all the bolts with a Bolt Hardware engine kit. If you are around the Ohio area and need some work done I highly recommend Gary at GBR. Very clean and organized shop. Can tell he takes a lot of pride in his work.
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Before & after of the head.
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New pipe mount.
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Ready to shred in 2020! 

Upcoming plans are to replace the OEM rear caliper and brake disc guard with Light Speed Carbon and a fresh set of Dunlop MX33 tires. At some point, I'd like to get the brake calipers and master cylinders cerakoted and add an oversized rotor kit on the front.

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1/20/2020 9:02 AM

I like the adapter bracket for using an older pipe on the newer frame. Is that custom or something you can buy? I have an 02 with 98 cylinder and mating Bill's pipe but haven't come up with a bracket yet.

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1/20/2020 9:19 AM

450exc115 wrote:

I like the adapter bracket for using an older pipe on the newer frame. Is that custom or something you can buy? I have an 02 with 98 cylinder and mating Bill's pipe but haven't come up with a bracket yet.

He said the mount was from a CR250 and it bolted right up. I'm not sure what year the mount is from though.

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1/24/2020 8:38 PM

450exc115 wrote:

I like the adapter bracket for using an older pipe on the newer frame. Is that custom or something you can buy? I have an 02 with 98 cylinder and mating Bill's pipe but haven't come up with a bracket yet.

DaBaum44 wrote:

He said the mount was from a CR250 and it bolted right up. I'm not sure what year the mount is from though.

Looks like a 02-07 CR250 exhaust mount. Found one on eBay and should have it next week, hopefully it works.

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2/10/2020 12:19 PM

Finally scored a Pro Circuit pipe. Has some small dents and scratches but the plan is to have my local plating shop strip the nickel plating and then I'll send it to Pipe Repair in Oregon. Will pair it with a Pro Circuit Ti2 silencer. Looking forward to testing it against the FMF system in the spring and seeing how good Pipe Repair can make it look.
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2/10/2020 1:35 PM

I believe the best pipes were the Noleen or the Bills pipe for the 96-04 YZ125 motors. I have a Bills on mine I just need to finish it. Lol

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2/10/2020 2:27 PM

450exc115 wrote:

I believe the best pipes were the Noleen or the Bills pipe for the 96-04 YZ125 motors. I have a Bills on mine I just need to finish it. Lol

Thanks for the insight. I've never heard much about Noleen but heard good things about Bill's. My only thing with the FMF is it doesnt want to rev out as far as I think it should. Otherwise its great. I've been told from some folks who raced back in the day that a Pro Circuit will rev farther.

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2/11/2020 6:40 AM

You want to find a FMF SST for mid top. The fatty was more of a mid pipe. Challenge with the SST is tended to run a little leaner so you have to jet a little fat in the middle.

Noleen was a big part of Yamaha's success in the 90s to early 00s when they switch to MB. Pipes were considered the best for the YZ. I'm still trying to find a 97/98 for my old 250 (which was ported by Noleen back in the day).

Bills pipes are just good pipes, I think he supported Suzuki a fair amount but they tend to wake up most brands.

PC was always a mid/top pipe but some felt they were a little flat on top compared to the Noleen and Bills.

Another option is a dynoport pipe who makes a mid top specifically.

Cool bike and can't wait to get my 02 done.

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2/11/2020 8:35 AM

Nice clean looking bike ! And you race it also !!

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2/11/2020 8:48 AM

Bike looks great!

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2/11/2020 3:51 PM

450exc115 wrote:

You want to find a FMF SST for mid top. The fatty was more of a mid pipe. Challenge with the SST is tended to run a little leaner so you have to jet a little fat in the middle.

Noleen was a big part of Yamaha's success in the 90s to early 00s when they switch to MB. Pipes were considered the best for the YZ. I'm still trying to find a 97/98 for my old 250 (which was ported by Noleen back in the day).

Bills pipes are just good pipes, I think he supported Suzuki a fair amount but they tend to wake up most brands.

PC was always a mid/top pipe but some felt they were a little flat on top compared to the Noleen and Bills.

Another option is a dynoport pipe who makes a mid top specifically.

Cool bike and can't wait to get my 02 done.

That's good to know. Thank you for the info. I called Bill's at one point and they don't make them anymore, which isn't surprising. Said they could make one if I took my bike to their shop but I'm in Indiana.

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2/11/2020 3:55 PM

RAD60 wrote:

Nice clean looking bike ! And you race it also !!

Thanks! I definitely try to ride or race any bike I have for a fair amount of time before having them modified.

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2/12/2020 6:03 AM
Edited Date/Time: 2/12/2020 6:11 AM

DaBaum44 wrote:

Headed back to the shop for the final pieces of the build. I never touched the clickers prior to riding the bike, and my mechanic discovered that the adjusters on the left fork don't engage. Going to have this fixed, and get the forks and shock rebuilt.

Also time to get the top end changed, some porting, and hopefully Pro Circuit and the distributors pull through with getting the pipe in. Been on back-order for 6+ months.

Here's a sneak peek of the graphics. My brother designs custom graphics, so he hooked me up with a clean design.
More of his work can be seen on Instagram: @dabaum_designs

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Some Vital members have probably seen his work on Zesiger 112's YZ 250. Zesiger 112 provided the design and he helped bring them to life.

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2/12/2020 6:05 AM

DaBaum44 wrote:

Headed back to the shop for the final pieces of the build. I never touched the clickers prior to riding the bike, and my mechanic discovered that the adjusters on the left fork don't engage. Going to have this fixed, and get the forks and shock rebuilt.

Also time to get the top end changed, some porting, and hopefully Pro Circuit and the distributors pull through with getting the pipe in. Been on back-order for 6+ months.

Here's a sneak peek of the graphics. My brother designs custom graphics, so he hooked me up with a clean design.
More of his work can be seen on Instagram: @dabaum_designs

Photo


Some Vital members have probably seen his work on Zesiger 112's YZ 250. Zesiger 112 provided the design and he helped bring them to life.

He also did another bike I built with a friend.
Plan on using him again this year for helmet wrap, updated graphics for yz, and maybe sticker sheet of small decals. Photo
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2/12/2020 4:29 PM

Zesiger 112 wrote:

He also did another bike I built with a friend.
Plan on using him again this year for helmet wrap, updated graphics for yz, and maybe sticker sheet of small decals. Photo
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Sounds good! Both of those bikes are super clean!

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3/29/2020 5:19 AM

I forgot how good these bikes are. Here is my 02 that was a buddies bike that was stolen and returned missing wheels, topend, pipe and other various parts.
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I sourced a good 98 top end, wheels, Bill's pipe, radiators, new plastic, and probably a couple hundred bucks of odds and ends to get it back together.

Took it for a warm up ride yesterday and man is it quick. My last race bike was a KTM 450 and the past few years I've been racing vintage big bores so I wasn't expecting much out of the 1/4 liter but it is quite zippy on the pipe! Not quite the show quality you guys have built but not bad for a low budget rescue! smile
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3/30/2020 7:09 PM

I noticed you went back to am 03 from brake. I had an 03 yz anfew.years back and swapped out for the master off of an 08 model and its a.big improvement

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"If you feel in control, you're not going fast enough" ~Mario Andretti

3/30/2020 7:18 PM

Phillip_Lamb wrote:

I noticed you went back to am 03 from brake. I had an 03 yz anfew.years back and swapped out for the master off of an 08 model and its a.big improvement

I can't remember the exact year, but I'd definitely agree that it makes a big improvement.

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8/3/2020 9:57 AM

Installed new Renthal chain and sprockets, Works Connection axle blocks and Bolt sprocket bolts. The rear sprocket I removed had some rub marks from an aftermarket UFO chain block I installed. Had to cut a few millimeters from the rubber block surface to resolve that.

Still waiting on a rear rotor/caliper carbon fiber cover from Light Speed. If anyone knows another carbon manufacture that makes them for a 2003 YZ125 please let me know! Been 6+ months since I ordered one and Light Speed always tells me they are still waiting to produce more of them. To be fair, they did say I wouldn't get charged until the part ships.

Other than that the entire bike has basically been gone through besides the rear brakes. Might tackle those as a winter project with some coatings.
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