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.JC-Yamaha-YZ250-b3Like 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.

The motor was blown up and we did not calculate the total rebuild cost, but at least it wasn’t a four-stroke! It was as tight and fresh as a brand new bike and ran a crisp and strong as the 2016 we had along with us.

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.JC-Yamaha-YZ250-b2

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.JC-Yamaha-YZ250-6

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.

JC-Yamaha-YZ250-b4We 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.

The bike was pretty blinged out but the powder coated frame and swingarm definitely helped get the bike looking fresh. The black color made it look heavy but tough! Tusk Impact wheels are an affordable complete wheel replacement and we have been testing them on other bikes with positive results.

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. JC-Yamaha-YZ250-b5

Here is how Jay explains the building of the bike:
The Yamaha YZ250 has been a main stay for the last ten years and a top choice of many off-road enthusiasts. The bike has remained mostly unchanged from Yamaha until 2015 when the bike got some style upgrade points but no performance improvements.   There any many riders who feel this is a great all-around bike for moto and trails. Until the new 2016 YZ250X there was no purpose built trail two-stroke from any of the Japanese manufactures.
So, we set out to build yet another YZ250 to see how good we could get it.
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.JC-Yamaha-YZ250-7
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.JC-Yamaha-YZ250-9
We had Race Tech go through and put all new Pivot Works parts in our forks and shock. The valved and set up the suspension for a larger rider to do off-road racing and a little motocross.
For fuel we ran straight AV Gas since the pump gas nowadays is not very consistent.    We used jetting that is just a bit leaner than stock:
Needle stock in #2
Here is Jay’s parts list. Just about every part listed below can be purchased from Rocky Mountain ATV/MC.
Rocky Mountain ATV/MC  800-336-5437

Wrench Rabbit        515-473-9647

Full rebuild kit includng:
Hot Rods Complete Bottom end kit  Includes complete crankshaft, main bearing seal kit and complete engine gasket kit. Also includes transmission bearings.
Vertex Pistons Pro Replica Piston kit  (ring, pin and clips)


Millennium Tech          920-893-5595
Strip, re-pair damage and re-plate to stock size
Radiator straightening and bracing


Uni Filter                714-535-6933
Two-Stage air filter


Hinson Clutch Components         909-946-2942
Fibers, steels and springs clutch kit


FMF Racing        310-631-4363
Fatty exhaust
Shorty Factory 2.1 Silencer                               


MotoTassinari       603.298.6646
V-Force Reed Cage


Pivot Works               515-402-8000
Steering stem bearing kit
Fork Rebuild kit
Shock rebuild kit
Linkage rebuild kit
Swing arm rebuild kit


Renthal                 877-736-8425
Front Sprocket 14T
Rear sprocket  49T
604 Fat bars
Dual compound grips
Front and rear brake pads


AT81 90/90-21 Front
AT81 100/100-18 Rear


DeCal Works                    815-784-4000
Semi-Custom Graphics kit
Pre printed number plates backgrounds


Moto Seat                 951-258-5229
Custom Cool seat cover
Updated firmer seat foam


Works Connection    1-800-349-1475

Elite Clutch Perch
Radiator braces
Brake Caps
Oil filer Plug
Chain Blocks

Tusk                  800-336-5437

Impact wheel set with 18 Inch rear

270mm Oversized Rotor

Front Steel braided brake line

Rear rotor

Rear Brake Pedal


Brake bolts kit  Sprocket Bolts kit
Kick it Kickstand
Applied Racing      800-853-0555
Triple Clamp with 2015 mounting for front fender
Top bar mount for Scotts Stabilizer
San Diego Powder Coating   619-956-0987
Sandblasting, Powder coating black frame and swing arm, with superdurable clear, and “race prep masking’


Klotz Synthetic Lubricants                800-242-2489
R-50 Two-Stroke Pre-Mix


Suspension rebuild and service
Cycra Racing        740-929-0188
Full Plastic Kit in blue – New 1015 look
Impact Hand Shields
Chain guide and chain block
O-Ring Chain
Stock Yamaha Misc parts
Oversized Fuel Tank
Stabilizer (used and refurbished by Scotts)JC-Yamaha-YZ250-b6

Support Dirt Bike Test by buying through the links below: