Rebuilding a Yamaha YZ250 To New

How To Restore A 2006 Yamaha YZ250 To Almost Better Than New.   

When DBT got our brand new 2016 Yamaha YZ250X it wasn’t a week later we got a call from Jay Clark. Well known to those in motorcycle journalism, Jay will spoon feed editorial outlets hopped-up bikes of about any variety. Some magazines are catalogs of Jay’s bikes. He told us he bought a $1000 10-year old YZ250 and had made it better than the brand new bike.Like usual we didn’t believe him but who are we to pass up on am excuse to go ride someone else’s bike for a little while, with brand new Dunlop tires, none the less. We met up in the high desert for some riding and to see just how possible it is to make an old bike new. We have been doing a similar story with a much more novice bike builder and a YZ125 in a box so this will give readers some perspective when that bike is almost done. Here is a link to that story ongoing. We brought along our 2016 Yamaha YZ250FX as a target to see not only the differances in new and only but how the changes Yamaha made to the YZX (transmission, power delivery, suspension) compare to the aftermarket alternatives.

Jay’s YZ motocrosser converted to off-road definitely looked a lot more trick than our mostly stock bike and we’re pretty sure it would actually weigh a few pounds more on the scale. The bike fired right up and it was as tight sounding as a brand new bike. This is easy to do on a two-stroke when you replace the right parts (or all of the wear parts) and we have plenty of experience from doing this on many different bikes. But even with the simplicity of the two-stroke there are a lot of little things that can cause havoc if you are not aware of them. Jay knows what to look for and knows what is easy to replace and fix. Worn cases and missing components in the clutch or transmission can backfire the whole budget very quickly.

The first thing we notice was how tight the bike felt. Brand new in fact. Why? Because it was basically re-manufactured. When you take the time to replace the bearings in things like the swingarm, suspension and headset, all the areas of vibration are minimized or eliminated. Changing out worn levers and footpegs tighten things up as well. It isn’t cheap when it is all added up but it combines to produce a tight ride. A smooth pulling clutch and light throttle twist, like new, go a long ways in how a bike is perceived because this is how the rider reacts to it.

When we quickly found out it was set up for a 220+ pound rider so we were prevented from making any direct suspension comparisons except that the Race Tech valving wasn’t so stiff that it made riding the bike unbearable even with the very heavy springs. For us it gave the bike a slightly heavy feeling too as the wheels bounced on the small bumps instead of absorbing and being plush. The owner was very happy with how the bike worked and was confident it would handle his off-road riding and even some moto when asked to do so. Suspension is very personal and although spring rates are easy to figure based on weight, the internal valving is where communication with your tuner is important. We have been blown away with most of Yamaha’s standard suspension settings for average riders using the bikes for their intended purpose. But it only took one ride (another time) on a YZ250 off-road to show how much better the X is for that use.

We rode the bike along side our then-new Yamaha YZ250X on some GP-style tracks and then on a mountain single-track loop switching between the new and old bike as well as comparing them to a 2016 KTM 450XC just for kicks.

Where the project YZ was different was in the motor. Basically stock with an FMF exhaust and a Moto Tassanari reed system it felt like it had a heavier flywheel off the bottom when in reality it didn’t. The bike was not as smooth as the standard bike but it felt like it had more power when it came on and then it pulled with a lot more gusto in the mid-range. When you were moving and flowing this was great and it is more of a motocross powerband. In the tight you can feel the taller first gear ratio but the excellent Hinson clutch components never whimpered. For the heavier rider with more weight on the tire, the boosted power will not be an issue, only a plus.

So the question is, was the project bike better than the stock 2016 YZ250X? For the bike’s owner, for sure it was. Even if you calculated the costs between starting with the new bike and this $1000 basket case, there will still be a lot of mods the new bike would need jut in set-up for weight. It showed the advantages of the transmission ratios and there is no reason a mechanic with the cases split couldn’t change out some of those parts too. It shows how in depth you can get in rebuilding a bike or it is a warning about what it will take to get a basket case running again. Maybe the best lesson is in how keeping your already OK working bike fresh can save you in the long run and how to fix it up if something goes wrong. 

This bike in a basket was purchased for right under $1000 so we had some budget to make a full custom bike that would be close to new. The bike was pretty beat so rather than try to buff out the frame we thought we would just powder coat the frame and the swingarm black for a very custom look. Since the motor was blown up we went through it completely with an all new Wrench Rabbit kit. This has all of the parts for the full rebuild in one box. The cylinder had to be repaired by Millennium so they matched up the new Vertex Piston to the cylinder when it was replated.

We didn’t do any extra engine modifications—no cylinder porting or head mod— we wanted this thing to run good and be as durable as stock. The V-Force reed and FMF pipe are the extent of the real performance mods. On about any old bike the radiators have to be repaired as new ones cost way to much and can be over $300 in many cases. ICW does a reasonable cost repair and they are like new.

Wrench Rabbit www.wrenchrabbit.com        515-473-9647

Works Connection  www.worksconnection.com    1-800-349-1475

Tusk  www.tuskoffroad.com                  800-336-5437

Impact wheel set with 18 Inch rear

270mm Oversized Rotor

Front Steel braided brake line

Rear rotor

Rear Brake Pedal

Shifter

Stabilizer (used and refurbished by Scotts)

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