The Last Factory YZ125

Yeah, Don't get me started on that Tim Taylor 718 character....You can add me to the list of victims

Back to the good stuff.

The factory clamps were a little difficult. I bought all new pivot works bearing kits for this build, but the headset bearings are not standard. The stem has different dimensions and the top and bottom bearing I.D. are nearly the same whereas the stock set up has a bigger differential in diameter on the bottom bearing than the top. Basically there is nearly no taper on the factory stem compared to the stocker. I sent the bearings, races and seals to pivot works to have them matched and they said I'd have to send them to Japan if I wanted to replace them. Evidently Yamaha uses different bearings and stem combinations to tune handling, which is interesting.

Luckily the bearings and races were still in good shape so I just cleaned them up and re greased them. If they were worn, I'd go through the hassle of tracking down a new set in Japan, but there's no need.

The Suspension bolted up nice with Ti top shock bolt and linkage bolts. Looks a lot cooler with the kashima and TiNi tubes and two piece shock body. Mettec had one Ti YZ front axle left so I checked fitment with the front wheel/axle/spacers off my 06 YZ250 before buying it. I wasn't sure if the lugs on these forks would be the same, but they are.

Thanks for checking it out!

I did find out some history on the engine. In 2005 the AMA had implemented those oxygenated fuel rules that made it harder for two stokes to compete. YOT's former engine guy said they had a pretty extreme engine package that required very expensive VP fuel. He said it was like $80/gal, but I find that hard to believe. The compression and port timing wouldn't allow using even C-12 so they replaced the cylinder on this bike with a stocker so it could be run with pump gas. The cases were the original race modified parts, just the cylinder and head were replaced.

I brought the engine to John Mitchell of JM Racing here in Houston. He has a good porting package for the YZ125 that I've heard people rave about so I asked him to port it and match it to the cases.

On dissassembly, I noticed right away how much material was removed from the cases. It was left rough for atomization of the fuel/air mixture.



Here's a view of the modified intake.



Some cool Ti Pieces throughout the engine





Cutting the cylinder and head





The Ignition is a Vertex unit set to "no 1".

I just cleaned and addressed a couple scratched areas on the swingarm with out removing the anodizing. If the swingarm was in bad shape I would have removed the anodizing with EZ Off oven cleaner. There's probably other methods out there, but that's what I use. Wear gloves though because it's caustic stuff. I prefer to keep swingarms anodized if possible because the surface is more durable and doesn't require so much maintenance to keep looking nice. Lots of factory teams remove the anodizing to give it that cool, raw-aluminum factory look though.

The throttle tube is a black anodized aluminum piece. I didn't think to compare the diameter of the cam but I will now that you bring it up. I can tell you the spring on the slide has been modified by shortening it so it snaps real nice.

So around this point I started to ask myself if I really wanted to build this bike back exactly like it was. I really want to ride it rather than make it a garage queen so I am veering off from building it back to OG YOT form. For example, I'm a big fan of Honda front brakes. They just feel better than the Yamaha calipers and Master cylinders. Honda's Nissin components are lighter than Yamaha's as well. The Levers they used were those ARC unbreakable type. The clutch perch was the Sunline billet one. It had Ti Hardware, which is cool, but you can get Works Connection Elite perches with the pivot bearings and more functional quick adjust. Works Connection sells a Ti bolt kit too. I think they are the best available so I'm going that route.

I'm going to keep all the original stuff, so when I'm done I can always return it to 2005 Metcalfe trim if I want to. I found these original Plasticwerks Venturi front number plate and front disc guard as well as a set of GYTR blue side number plates.



I put a new airbox on as the old one had a crack in it.



If your concerned about the weight of the stock steel air filter bolt, don't be. This baby has a factory two-piece titanium one with an aluminum wing nut threaded on! Its those little nuggets of trickness that makes you smile.

How do you move this thread to the new bike builds section?

I've been hoping that a of original 2005 Yamaha of Troy Graphics would pop up on Ebay, but no luck. They have holographic inlays so I don't want to get them reproduced. Years ago I bought a couple of the first year JGR graphics kits that were made by N-Style on ebay cheap. I put a set on my YZ250 and had N-Style make print up some matching number plate backgrounds.



I think I'm going to use them on this YZ125 as well and have matching YZ's. Here's the 125 backgrounds:



Think! Technology made a run of YZ125/250 seat foam awhile back. They were expensive, but wow, they are light. Throw it up in the air and it floats down like a feather. Over a pound lighter than stock. I brought it to a local upholstery shop so I could use their air staple gun.

Thanks RJ! I appreciate you looking.

I'm riding this one so I am glad I went the direction I did rather than just restoring it to original YOT.

Maybe we can do some trading if you find those graphics for those KX parts.

Hey thanks for the link Blake! Did you ever listen to that PulpMX podcast with Rich Taylor where he talks about his 96 CR250 that had the Boswell carb? He holeshot the Washougal national that year and claimed his stock CR with the Boswell was faster than the factory Honda. He was testing for Honda at the time so I guess he would know.

Braaphole: Send me an email at flesche917@gmail.com. I'll let you know when I'm riding, or your welcome to come check it out at my shop. I live 15min from Three Palms.

DJ

Here's a pic with the engine installed along with new plastic and airbox. I don't like the updated plastic as much as the old stuff so I went original OEM. I'm pleasantly surprised with OEM Yamaha parts prices!

You can see the Vertex ignition off to the side. It mounts up in the space between the radiators with a Ti bracket. There is a connection plug that I learned is for a handlebar mounted mapping switch on the handlebar. The bike didn't come with this switch, though.



The bike came with a FMF factory pipe that was dented. It's just a standard issue FMF pipe so I could just get a new one to go with the trick Ti FMF silencer which has a really cool Ti bracket welded on.



I think this bike screams for one of those Ti/carbon PC silencers, though! As with the front brake, PlasticWerks number plate/front disc guard, Clutch perch, etc; I'll hold on to these parts if/when I return it to original.

Check out MXA's Two Stroke Tuesday! Basher had some good timing featuring Metcalfe's YZ just as I am finishing this bike.

http://motocrossactionmag.com/news/two-stroke-tuesday-the-last-works-12…

So here's the nearly finished product after I fired it up and took it for a rip. It's crisp, but after riding 450's for so long, its hard to gauge. Still, for a 125 it is pretty fast I guess. I need to meet up with my buddy Rob who still rides his 125 and compare. I'll get some pics and maybe a video. I need to weigh it up, too.

They are Renthal 997 bend, which has the same dimensions as the 971 7/8" bar that comes stock on Hondas these days. The magnesium bar mounts are high, forward and solid mounted. There is a "10" stamped into the bar mount, so I assume it means they are 10mm higher. There is multiple mounting holes so you can adjust the bar mount location front to back. In pics it looks like Metcalfe rolled them way back. I'm taller so I keep them neutral and they feel good like that.

I updated the bike with the correct Yamaha of Troy 2005 graphics seat cover and the rest of the bits I collected. Plasticwerks front number plate and front disc guard, carbon ignition cover and returned to the the FMF pipe and silencer, ymc clutch perch and front brake, etc.

Rolled it outside and took some pics: