Honda XR250 BAJA Fork Springs: Measuring the Free Length Before WPC Treatment

Hello everyone.

Rust on the inner tubes of my Honda XR250 BAJA (the Japan-market XR250 / MD30) front forks led me to rebuild the forks. Along the way, I've had the inner tubes re-plated and looked into the fork springs.

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Hello everyone.Today I'd like to share a mistake I made: running XR250R (ME08) front fork springs on my XR250 Baja.First, please note that this article is just my personal impression. I don't expect it to apply to everyone. Many owners of the XR Baja or the XR250 (MD30, the Japanese-market model) consider fitting parts from the ME08, the XR250R racer, to improve off-road performance. Swapping the front fork springs comes up often, but on my Baja, forks with ME08 springs inside were not a good match. In this article, I describe how forks with ME08 springs felt on my Baja, ...

: Honda XR250, BAJA, & XR250R Fork Springs: Real-World Measurements Reveal the "Model-Year Trap"

In this article, we’ll be pulling the front fork springs from three of Honda’s iconic dual-sport and off-road machines—the XR250 (MD30), the XR BAJA, and the competition-only XR250R (ME08)—to perform a thorough side-by-side comparison of their specs, free length, and internal structures. We’ll also dive deep into the "model-year trap" hidden within the factory service manuals regarding subtle spec changes over the years. Hey everyone! Today, we’re doing a deep dive into the suspension setup of the Honda XR series, a lineup that still commands a massive cult following among off-road enthusiasts. Right now, I have three different sets of ...

I also wet-blasted the bottom brackets (axle holders).

: Wet Blasting Fork Axle Holders with Glass Beads and a Karcher (Honda XR250)

Wet blasting the aluminium fork axle holders of a Honda XR250 (XR250 BAJA) with #120 glass beads and a Karcher: masking the anodised tubes, baking soda vs glass bead results, and why the clean-up put me off.

So, just as I was thinking, "Right, time to finally assemble the forks," I checked the fork springs I'd kept in storage, and...

The XR250 BAJA front fork springs laid out before sending them for WPC treatment

Rust...

I removed the rust with Scotch-Brite.

Then I measured the free length of the springs.

Measuring the free length of the short spring A from the XR250 BAJA forks with a digital calliper

Spring A (the short spring that sits at the top when fitted) measured 44.31 mm.

Measuring the second spring A to compare it with the service limit in the service manual

The other spring A measured 44.4 mm.

When I checked the service manual, both were past the service limit (they had shortened)...

Spring A	Free length (new)	Service limit	My springs
1	45.6mm	45.1mm	44.31mm
2	Same	Same	44.40mm

I looked for new genuine springs just in case, but they've been discontinued...

Measuring the free length of the long spring B before WPC treatment

Pulling myself together, I also measured spring B (the spring that sits at the bottom when fitted).

Measuring spring B against a steel rule to check it is within the service limit

This one was 390.5 mm.

Measuring the second spring B against a steel rule

The other one was 390.5 mm too.

Spring B	Free length (new)	Service limit	My springs
1	390.3mm	386.4mm	390.5mm
2	Same	Same	390.5mm

I only read these off a steel rule by eye, but the free length came out the same as new.

For both springs A and B, the service limit seems to be about 99% of the new length.
As there are no genuine A springs left, new ones would have to be made as one-offs. Looking online, that seems to cost around 20,000 to 30,000 yen per spring. Because they're short (less material), it might be a little cheaper, but a one-off isn't a realistic option for me on cost.

But if I keep using them as they are, they'll obviously keep sagging, so I decided to send them in their current state for WPC treatment (a Japanese micro shot-peening surface treatment). WPC treatment is said to help prevent springs from breaking and sagging.

That's all for today.
Once the WPC treatment is done, I can start assembling the forks! Or so I hope...

I've also written a guide to overhauling the XR250 / BAJA front forks, from disassembly to oil, springs and re-plating, with the steps and costs.

: Honda XR250 / BAJA Front Fork Overhaul Guide: Steps, Costs and Model-Year Differences

A summary of my XR250 BAJA (MD30) front fork overhaul: the order of the work, re-plating costs, spring differences between the XR250, BAJA and XR250R, mixing fork oil to match Honda's viscosity, and axle thread sizes by year.