Yz 125 vs Sx 125 project bike

I haven’t “built” either of these bikes but I’ve worked on a ton of YZ125s and a good amount of KTM 125/150s. 

YZ has virtually been the same motor forever, tons of videos, parts are everywhere and cheap, and anybody who does any kind of motor work knows how to set them up and make them pretty good for cheap. Suspension is great as well and most tuners can dial it in easily. 
 

The 2008 KTM 125SX isn’t an incredible bike, a lot better than the previous generation but was still PDS and just had that KTM feel. The forks on those bikes are arguably the best production WP forks, and the KTM 125s always were fast despite their odd handling. Parts are pretty available, the 125 motor was pretty similar for a number of years. 

I’d say if you want an easier/cheaper project to learn and build then go for the YZ, if you want to be different go for the KTM, nothing mechanically is very different between the two, but a lot easier to find information for the YZ IMO, if it’s going to be your main rider, I’d pick the YZ in that situation. 

They both have pluses and minuses. 

That style ktm engine like the yz where used for a long time. 

Yz125 05 thru 21.

Ktm roughly 98 thru 15 some variation in cylinders and crankshafts. Plus the engine was shared with the 200. 

I owned a 06 yz125 for 15 years from New. The ktm engine is a lil bit stronger. Yz is lighter weight. The ktm engine is bigger heavier is part of why. 

Yz is like 202lbs the ktm 208 lbs 

I rode my friends 05 125sx when I got my 06 yz125. They were very close in power his ktm had a lil more on the top end. 

I like the hydraulic clutch more myself but the yz's cable setup is simplistic. 

Unless you are a sensitive to suspension pro. You might not notice the difference between the linkage n the pds. The rear pds is a bit more sensitive to proper spring rate for rider weight. 

The yz might be a lil easier cheaper good bike. I wouldn't hesitate to get another one. 

The ktm is equally as good it has at least an oem way of making it a 200. And the engine can be put into ktm 125 chassis up to 2015. 

Ultimate decision factor is what one is in better condition. Both can be something awesome. 

Between those two bikes? The Yamaha all the way. Parts are readily available and cheap. That era KTM was from before they became such a powerhouse.

I would choose the Yamaha all day every day... tons of parts everywhere, and still pretty awesome bikes.

Project bike has to be the yamaha.... unless you want a more difficult and expensive project!

If you could get a KTM with linkage without breaking the bank too much... I'd go for that

I raced the 08 KTMs are they were great bikes, a progressive spring on the rear gets pretty close to mimicking linkage.

But for the price and simplicity of the 06+ YZ, its really hard to beat. I believe with only plastic and airbox you can convert to up to 2021 plastic, and with subframe seat and tank you can convert to 22 plastic, but don't quote me on that.

YZ. 

Agree with the others on the YZ. Cheaper, tons of parts and lots of info.

Motor is still easy to work on. The steel frame YZs are great bikes. If you can get a hot deal I would jump on it!

YZ all day, more parts availability means more directions you can take your build in.