Yamaha YZ250FX / WR250F Long Term Wrap-Up

A Year With Yamaha’s New 250F Off-Road Bikes

At Dirt Bike Test we take bike testing serious. And we go the extra steps to stay on top of the curve and pass the information we have onto you. Learning all the time. So when Yamaha agreed to let us keep the 2015 YZ250FX and 2015 WR250F for a year, we rode them like we owned them intending to put 100-plus hours on each. We got really close. Ninety nine on the FX and approximately 125 on the WR. Both bikes were raced, trial ridden, used for course set-up at events and generally just having a fun time riding.

Our first tests spell our how we feel the bikes perform (http://dirtbiketest.com/bike-tests/2015-yamaha-yz250fxhttp://dirtbiketest.com/bike-tests/2015-yamaha-wr250f/) and over the course of some updates (easily searched here on DBT) we talked about some modifications we did and how the bikes were holding up during the year. Then as a finale for the FX, we raced it in the 24-Hours of Glen Helen and then tore it all apart to see how the bike really looked, from the inside out.15-wr250f-teardown-41

The captions on the photos below will give you the details but the plain and simple fact is that Yamaha 250cc four-stroke racer is extremely durable and we have nothing but high praise for the condition it was in. Even after some abusive conditions. After all that riding and racing the measurements listed below will give you an indication of how good of shape some of the wear items were in.

Yamaha’s Gerrad Capley helped with the tear down and was tasked with putting it all back together. Now he is a YZ250FX expert.

The only part that we felt really needed to be replaced after 100-hours was the rod and wrist pin even though it was not quite out of spec just yet, it felt looser than we like. The piston, ring, cylinder and valves were all in the middle of the range when measured and they looked just as good. In reality, since the engine was all apart, a smart owner would go ahead and replace most of the wear items. Had we not disassembled the head for inspection, after seeing it there is really no reason to touch the valves aside from a clean up.

The engine is actually very easy to work on and came apart easily.

Inside the bottom end and transmission the gears were pristine. It appeared some debris had made a trip through the oil pump but there was no loss of pressure or aftereffects from this. Even the clutch basket looked great with very little wear on it’s fingers.

We inspected each piece as the bike came apart before laying it all out in a photo studio.

The chassis, like most aluminum framed bikes was in excellent condition and had no signs of stretching nor were any cracks visible. We did not pull the suspension apart as it had just been serviced before the 24-Hour and everything looked fine, we just replaced the fork seals as preventative while doing a slight revalve for the smaller riders who would be racing the bike. The seals on the bearings in the headset, swingarm and suspension were all in great shape and the grease inside still present and in good shape. This after a year of pressure washing too. In reality any of the chassis damage was purely cosmetic and with a set of new plastic this bike would be ready for another 100-hours and looking good doing it.

We weighed a lot of the components to see how much they weigh. It is interesting to compare between bikes when you have this information.



1) Valve Clearance: Intake – 0.12mm (Both Intake Valves) (Spec – 0.12 – 0.19mm)
Exhaust – 0.17mm (Both Exhaust valves) (Spec – 0.17 – 0.24mm)
2) Piston Skirt O.D. 76.968 mm (Spec = 76.955 – 76.970mm)

3) Cylinder Bore: 77.000 mm (Spec = 77.000 – 77.010mm)

4) Piston Ring End Gap: 0.15mm (Spec = 0.15mm – 0.25mm)

The cylinder head was in excellent shape including the cam bearing surfaces and the valve guides and seats. Of note was the casting imperfections inside the intake tract which would indicate a good tuner should be able to get some additional power and performance out of this engine with head flowing. Carbon buildup was minimal for the amount of time on the bike and the general poor quality of gas these days.
The cylinder showed the normal polishing and some very small imperfections from debris getting in, but it was minimal and it was still in spec.
The piston had a light coating of carbon but very little wear for 100-hours. The skirts were minimally polished for the time and the ring grooves still tight. Even the piston pin was tight on the piston.
The only concern inside the engine was a slightly loose piston pin in the small end of the rod. There was no visible sign of wear or an indication of a lack of oil on the parts but it felt a little loose in a twisting motion. A new pin would likely tighten it up enough but a smart owner would replace the rod as well.
This picture shows the ring end gap which was well within spec. Not letting dirt get into the engine has a lot to do with long service intervals on wear parts that should be protected from outside elements.
The cam looked beautiful. Even the cam chain and its sprockets, specifically the smaller one on the crank was in great shape.
The Yamaha’s valves had normal carbon deposits but really looked like they had been living a stress free life. Typically a source of concern on modern high-performance four-strokes, it looks like the YZ’s design does not put too much strain on these parts from the close inspection we took of them. In our estimation they could easily go another 100-hours. Not floating the valves or over-revving the motor really helps but we also had fast young riders on the bike a lot of the time.

Here is the complete engine all all laid out and pretty. There were no surprises lurking inside. With a few parts and a gasket kit the bike would be fresh like new and ready for 100-more hours. For such a compact engine the parts appeared as if they were overbuilt based on the little wear we saw. this is a great thing for riders who like to keep their bike for more than a year or two and reaffirmed our high praise for Yamaha’s durability.
The most worn out part on the bike? The neglected chain guide. It was ripe for some replacement parts here.
Coming in a close second was the countershaft sprocket. It was time for a chain as well.
The suspension was serviced three times during the bike’s year and fork seal life isn’t the best. A revalve for lighter riders before the 24-Hour gave the bike some added plushness and a little more bottoming resistance for our younger and faster riders.
It was time for brake pads for sure. Even the lubrication on the caliper pivots was still in good shape after a year and never being serviced.
There was still sufficient grease on all of the different sealed bearings on the bike and we have seen a noticeable improvement from Yamaha in this area in recent times. Our bikes do not get the excessive wet riding nor the humidity of some areas but we tend to make up for it with aggressive pressure washing. We did not expect the bearing to be so pretty and greasy.
The chassis on the FX gets pretty busy, especially the wiring harness and all of its sensors spread across the bike. The spaghetti octopus of a wiring harness could spell a nightmare diagnostic issue but Yamaha painstakingly routes it away from danger and hooks it to safe places. That isn’t to say you’d better take pictures and make notes on it’s routing if you frame your bike so you don’t run into issues. Chassis hardware was in excellent condition even if the tools required (different sizes) seemed a little excessive.


Our bikes spent a year getting used in most every environment we could put it through. We have only positive things to say about the bike from a durability standpoint which is great since that is a big concern for riders as soon as they are sold on the performance. The FX as a racer and the WR more as a trail bike positions Yamaha right there with KTM in this competitive off-road arena. Getting 100 hard hours out of a 250F speaks volumes about the build of the bikes and we are glad we go to do this.

If you have any specific questions about the our Yamaha YZ or WR 250FXs, ask away in the comments and we will do our best to answer the good ones.