CR125/CR250 PWK Air Striker Carb Upgrade: Is It Worth It?

Thinking about replacing the Mikuni TMX carburetor on your Honda CR125 or CR250 with a Keihin PWK Air Striker?

I installed a 38mm PWK Air Striker from a 1999 CR250 on my 2001 CR125, and the bike ran noticeably better afterward.

But there's something I wish I'd done differently: I never fully optimized the original TMX before making the swap. So I can't say how much of the improvement came from the PWK itself versus better jetting.

Since then, I've gained considerably more carb tuning experience, including recently dialing in a customer's 2017 YZ125 with a Mikuni TMX.

Here's what I'd recommend today, including which PWK fits, what to check before buying, and whether the conversion is actually worth the money.

Want to upgrade your CR125 or CR250 without spending $500 on a genuine Keihin? I've compared three options, from a genuine PWK to a $35 budget copy, including what I'd expect from each when it comes to tuning and reliability.

Compare PWK Carburetors & Prices

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PWK Air Striker vs. Mikuni TMX: Which Is Better?

Both the Keihin PWK Air Striker and Mikuni TMX can run well when they're in good condition and properly tuned.

The PWK Air Striker has two distinctive fins on the air-filter side of the carburetor, along with its venting arrangement. It's a popular carburetor on older two-stroke dirt bikes, and one reason riders like it is its clean throttle response.

In my experience, the PWK Air Striker tends to have a slightly sharper response at lower RPM, especially when riding trails where you're repeatedly opening the throttle from small openings.

I've also found it can be somewhat less finicky as riding conditions change, although no carburetor is immune to temperature, elevation or humidity changes.

The Mikuni TMX isn't necessarily a bad carburetor. For example, I recently tuned a 2017 Yamaha YZ125 with a TMX, and it wasn't particularly difficult to dial in.

The Honda and Yamaha applications don't necessarily use the same needles, slides or calibration. Engine characteristics and intake and exhaust design also affect how a carburetor responds.

So I wouldn't assume that every Honda TMX problem requires a carburetor replacement.

PWK vs. TMX at a glance

Consideration	Keihin PWK Air Striker	Mikuni TMX
Throttle response	Can feel particularly crisp at small openings	Can also respond very well when properly tuned
Jetting	Familiar tuning options and broad parts availability	Tunable, but components and calibration vary by model
Changing conditions	In my experience, often relatively consistent	May require adjustment depending on setup and conditions
Installation	Conversion may require fitment checks and new jetting	Already fits if it's the original carburetor
Cost	Carburetor plus any required parts and tuning	Often cheaper to clean, rebuild, and tune the existing carb

My recommendation: If your original TMX is in good condition, try diagnosing and tuning it before assuming you need a PWK. If you want a different carburetor or prefer the PWK's response characteristics, the conversion may still be worthwhile.

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My 2001 CR125 PWK Air Striker Conversion

I installed a used 38mm Keihin PWK Air Striker from a 1999 Honda CR250 on my 2001 CR125.

I paid about $95 for the carburetor at the time.

The bike ran well with the PWK, and I remember it feeling noticeably better than it did with the original TMX. That was almost 15 years ago, though, and I didn't do a controlled back-to-back comparison with both carburetors fully optimized.

I also suspect I could have fine-tuned the PWK further with what I know about jetting today.

That's why I consider my old settings a documented example, not a universal jetting recommendation.

My recorded CR125 PWK jetting

Component	Setting in my notes
Bike	2001 Honda CR125
Carburetor	1999 CR250 38mm PWK Air Striker
Main jet	182
Pilot jet	48
Throttle slide	#5.5
Needle	R1470D recorded
Needle clip	5th position noted, with a plan to move to 3rd

I can't confirm which needle clip position was the final, best-running setting. My notes also contain an earlier R14 needle reference.

Don't copy these settings blindly. Your engine condition, exhaust, fuel, elevation, temperature and riding style can change what jetting works best.

The important takeaway is that the PWK conversion worked well on my bike, not that every CR125 should use a 182 main jet and 48 pilot.

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Looking for a PWK Air Striker for Your CR125?

I used an older-style 38mm PWK Air Striker from a 1999 CR250 on my 2001 CR125.

If you're planning the same conversion, start by checking the genuine Keihin options and used OEM carburetors before deciding whether an aftermarket replacement is worth trying.

• Check Genuine Keihin PWK Availability
• See 38mm PWK Options on Amazon

Remember: For the 2000–2003 CR125 with the original TMX, look for the 91mm long-body screw cap top PWK Air Striker without TPS and verify the fitment before ordering.

Affiliate disclosure: I may earn a commission if you purchase through the Amazon link, at no additional cost to you.

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How to Identify a PWK Air Striker Carburetor

Not every Keihin PWK carburetor is an Air Striker, and not every PWK Air Striker has the same body dimensions or features.

Before buying one, look at these details:

• Air Striker fins: The two fins on the air-filter side help distinguish an Air Striker from a standard PWK.
• Carburetor body length: Different versions can have different overall lengths, which affects how the carb fits between the engine intake boot and airbox boot.
• Top cap: Some versions have a threaded screw-on cap, while others use a cover secured by two screws.
• TPS: Some applications use a throttle-position sensor. Check whether your bike originally had one and whether the replacement is compatible.
• Throttle cable and choke arrangement: Make sure the replacement works with your bike's controls and has sufficient clearance.

A carburetor that looks similar in a listing isn't necessarily a direct replacement.

Long-Body vs. Short-Body PWK: Which Fits a CR125?

One of the biggest things to check when converting a Honda CR125 to a PWK Air Striker is the carburetor's overall body length.

The 2000–2003 Honda CR125 models with the original Mikuni TMX use an approximately 85mm-long carburetor body without a throttle-position sensor (TPS).

For these bikes, the older-style 91mm long-body Keihin PWK Air Striker without TPS is the version I recommend looking for.

That's the style of carburetor I used on my 2001 CR125.

Carburetor	Body length	TPS
Original Mikuni TMX (2000–2003 CR125)	85mm	No
Older long-body Keihin PWK Air Striker	91mm	No
Other PWK versions	Varies	Depends on model

Although the long-body PWK is approximately 6mm longer than the original TMX, it's the version I used successfully for this conversion.

Important: Not every carburetor advertised as a 38mm PWK Air Striker has the same body length or TPS configuration. Verify the actual dimensions and photos of the carburetor you're buying rather than relying only on the model name.

If you're converting a different CR125 or CR250 model year, check the original carburetor and intake dimensions before assuming the same PWK will fit.

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Which PWK Air Striker Fits a Honda CR125 or CR250?

This is where I'd be careful.

Honda used different carburetor arrangements across CR125 and CR250 model years, so there isn't one PWK that should be described as a guaranteed bolt-on replacement for every bike.

Honda CR125

On my 2001 CR125, I successfully used the older-style 38mm PWK Air Striker from a 1999 CR250.

That makes it a useful reference point if you have a similar bike.

However, it doesn't guarantee the same carburetor will fit every CR125 model year without changes to the intake boot, airbox boot, throttle cable or installation procedure.

For the 2000–2003 CR125 models originally equipped with the 85mm (overall length) Mikuni TMX without TPS, look for the older 91mm (overall length) long-body PWK Air Striker without TPS, like the one I used.

Honda CR250

The correct replacement depends on the year and the carburetor already installed.

Some CR250 models came equipped with a Keihin PWK, while other years used different carburetor configurations.

Before buying a replacement, identify your existing carburetor and verify its physical dimensions and electronics.

What about TPS-equipped carburetors?

A PWK with a throttle-position sensor isn't automatically interchangeable with one that doesn't have a sensor.

Some conversions have been performed without using the TPS, but that doesn't establish that the arrangement is correct for every ignition system.

If your original carburetor uses a TPS, confirm the replacement's compatibility before removing or bypassing it.

36mm vs. 38mm PWK Air Striker: Which Should You Choose?

The 38mm PWK Air Striker is a common choice for CR125 and CR250 conversions, but 36mm versions are also available.

As a general rule, a smaller carburetor bore can increase air velocity at lower engine speeds, while a larger bore can provide more airflow potential at higher RPM.

That doesn't mean a 36mm automatically produces more torque or a 38mm automatically produces more horsepower. The result depends on the engine and how it's tuned.

36mm PWK	38mm PWK
Worth considering for lower-RPM response	Common option for higher-RPM performance
May suit a trail-oriented setup	May suit a more aggressive engine setup
Still requires proper jetting	Still requires proper jetting

For a CR125: I know the 38mm worked on my 2001 bike, so that's the conversion I can speak about from experience.

For a CR250: I'd make the decision based on the bike's existing setup, how you ride, and whether the replacement is physically compatible.

I wouldn't choose solely on the assumption that smaller is always better for trails.

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Where to Buy a PWK Air Striker Carb for Your CR125 or CR250

You don't necessarily need to spend $500 on a genuine Keihin PWK Air Striker to get your CR125 or CR250 running well, although it will likely be the most reliable.

There are several options, ranging from a genuine Keihin to inexpensive aftermarket PWK-style carburetors.

My best-value pick for someone on a budget would be the Nibbi Racing aftermarket carburetor, provided the correct size and dimensions are available for your bike.

Here's how I'd compare them.

Carburetor	Approx. price	What I'd expect
Genuine Keihin PWK Air Striker	$500	Best bet for consistent manufacturing quality, predictable tuning and long-term parts support
Nibbi Racing 38mm or 36mm	$130 / $100	Potentially good value with reasonable tuning consistency, but fitment and calibration still need checking
Budget Chinese PWK copy	$35	May work well after tuning, but greater risk of inconsistent calibration, poor fit or premature wear

Prices are approximate and may change.

Option 1: Genuine Keihin PWK Air Striker — Best for Proven Quality

If you want the option I'd have the most confidence in for long-term reliability and predictable jetting, I'd choose a genuine Keihin.

The main advantages are manufacturing consistency, established jetting components, and replacement parts availability.

The downside is the price. At around $500, it's a substantial investment in an older dirt bike.

Check Genuine Keihin PWK Availability

Verify the exact carburetor specifications before ordering. A genuine Keihin PWK isn't automatically the correct Air Striker version for your bike.

Option 2: Nibbi Racing 36mm or 38mm — My Best-Value Aftermarket Pick

If spending $500 isn't realistic, I'd consider a Nibbi Racing carburetor before jumping straight to the cheapest available copy.

At roughly $110 for the 36mm and $130 for the 38mm, it's a much smaller investment.

I would expect the Nibbi to be a more promising starting point than an anonymous $35 carburetor, but I haven't tested these particular models on a CR125 or CR250, so I can't guarantee easier tuning, better performance or longer service life.

Even a decent aftermarket carburetor may need changes to the pilot jet, needle, main jet or float level to run properly.

• Check Nibbi Racing 36mm Carb on Amazon
• Check Nibbi Racing 38mm Carb on Amazon

Before buying, verify the overall body length, spigot dimensions, throttle cable connection and TPS arrangement. Also confirm whether the model is an actual Air Striker-style carburetor or a standard PWK-style design.

Option 3: Budget Chinese PWK Copy — Cheapest Option

If your budget is extremely tight, there are PWK-style carburetors available for around $35.

Check Budget PWK Carb on Amazon

These can sometimes work, but I would expect a greater chance of needing additional setup or troubleshooting.

Potential issues include inaccurate or inconsistent jets, float-level problems, slide fit, machining quality and difficulty finding replacement components that fit correctly.

That doesn't mean every cheap carburetor is bad. It means I'd be prepared to spend extra time checking it before trusting the jetting.

And if you're paying someone else to diagnose and tune it, the cheapest carburetor might not be the cheapest option overall.

What About a Used Genuine Keihin PWK?

A used OEM PWK Air Striker can be a great middle-ground option, especially when you need an older long-body carburetor.

Some donor bikes worth investigating include:

• 1999–2000 Honda CR250: Older long-body PWK Air Striker without TPS
• Certain Yamaha YZ250 models: PWK variants, some with TPS
• Certain Kawasaki KX250 models: PWK variants, some with TPS
• Certain Suzuki RM250 models: PWK variants, some with TPS
• Certain KTM two-strokes: 36mm and 38mm PWK versions, including standard and Air Striker styles

These are possible donor-bike sources, not guaranteed fitment matches. Verify the exact year, carburetor design and dimensions before buying.

For a 2000–2003 Honda CR125 with the original 85mm Mikuni TMX without TPS, look for the older 91mm long-body PWK Air Striker without TPS, like the version I used.

The Air Striker has two distinctive fins on the air-filter side of the carburetor. Don't assume every carburetor advertised as a PWK is an Air Striker.

Where I Buy PWK Jets and Rebuild Parts

For tuning jets, I usually prefer Genuine Keihin or Pro X jets from Rocky Mountain ATV/MC. I'll also check Amazon if the correct genuine replacement jets are available for less.

For carburetor rebuild parts, I compare Rocky Mountain ATV/MC and Amazon based on price, availability and shipping speed.

• Main Jets - Pro X brand on Amazon
• Pilot Jets - Pro X brand on Amazon

Tusk and All Balls Racing are often good-value options for rebuild components, depending on what's available for the specific carburetor.

You can also find carburetor jets, needles and other parts at Jets R Us.

Whichever supplier you choose, verify the parts match your exact carburetor model. Don't assume every PWK-style aftermarket carburetor uses interchangeable Keihin components.

Disclosure: Some links on this page are affiliate links. I may earn a commission from qualifying purchases at no additional cost to you.

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PWK Air Striker Jetting: Where Should You Start?

A PWK conversion is not finished when the carburetor physically fits.

You'll still need to make sure the pilot jet, air screw, needle, slide and main jet work together for your bike.

Starting PWK Jetting for Honda CR250 and CR125

If you're installing a PWK Air Striker on your CR125 or CR250, these are some starting settings to consider.

They're based on the older-style Keihin PWK Air Striker carburetors and approximately 1,000 feet of elevation.

Jetting setting	CR250	CR125
Main jet	175	180
Pilot jet	45	50
Throttle slide	#7.0	#5.5
Needle	Cxx/R13xx family	Dxx/R14xx family
Needle clip	3rd position	3rd position
Air screw	1.5 turns out	1.5 turns out

Important: These are historical starting-point recommendations, not settings I've recently verified on both bikes. The needle descriptions identify broad families, not complete needle part numbers. Exact needle selection matters.

For the CR125, the 1999 CR250 PWK Air Striker with the #5.5 slide is a convenient starting point because that's the carburetor I used on my 2001 CR125.

For the CR250, the 2000 CR250 PWK Air Striker with the leaner #7.0 slide is another useful reference.

A #5.5 slide has a smaller cutaway than a #7.0 slide, which generally makes the mixture richer in the throttle range affected by the slide, assuming the other variables remain the same.

A 125cc and 250cc two-stroke can require different jetting even with the same carburetor, but that doesn't mean every CR125 must use richer jets than every CR250.

Also, my actual 2001 CR125 notes recorded a 182 main and 48 pilot, which differ slightly from the general CR125 starting numbers above.

Don't assume these settings are correct for your particular engine. Fuel, temperature, elevation, engine modifications and the condition of the carburetor all affect the result.

If you're using a Nibbi or another aftermarket PWK-style carburetor, these genuine Keihin settings may not translate directly because the jets, needle profiles and internal calibration can differ.

Different throttle openings emphasize different parts of the carburetor's fuel-metering system, and the circuits overlap.

Symptom or throttle range	What I'd investigate first
Hard starting or poor idle	Pilot circuit, air screw, fuel level and engine condition
Hesitation just off idle	Pilot circuit, air screw, slide and early needle response
Rich or lean behavior through the midrange	Needle diameter, taper and clip position
Poor performance at large throttle openings	Main jet, fuel delivery and overall engine condition
Inconsistent running across several ranges	Float level, intake leaks, carb wear or another mechanical problem

Start with the air screw and pilot circuit

Once the engine is warmed up and mechanically sound, the air screw is a useful way to evaluate the low-throttle mixture.

On a typical PWK two-stroke carburetor, turning the air screw out allows more air into the pilot mixture, making it leaner; turning it in makes the pilot mixture richer.

Don't assume there's one perfect number of turns for every bike.

If the engine only runs well with the screw near the end of its useful adjustment range, that may indicate the pilot jet or another part of the low-speed circuit needs attention.

Free resource: Learn how to adjust your 2-stroke air screw.

Don't tune around a mechanical problem

Before making large jetting changes, check for:

• Dirty or partially blocked carburetor passages
• Incorrect float height or fuel level
• Air leaks at the intake or crank seals
• Worn reeds or poor sealing
• Weak ignition or an incorrectly gapped spark plug
• Low compression or other engine problems

A carburetor swap won't fix a mechanical problem elsewhere in the engine.

For more help identifying the mixture problem, see my rich vs. lean dirt bike symptoms guide.

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Is the PWK Air Striker Upgrade Worth It?

For my 2001 CR125, yes. The 38mm PWK Air Striker conversion worked well, and I remember the bike running noticeably cleaner than it had with the original TMX.

But knowing what I know now, I'd approach the decision differently.

First, I'd make sure the original carburetor and engine were in good condition. Then I'd evaluate whether the TMX could be tuned to deliver the response I wanted.

If the bike still wasn't performing the way I wanted—or I simply preferred the PWK's response and tuning characteristics—I'd consider the conversion.

The PWK Air Striker is a legitimate option, but it's not a shortcut around proper diagnosis and jetting.

Want to make your two-stroke easier to start and smoother off idle? Start with my free 2-Stroke Air Screw Guide.

If you're ready for a more complete process for diagnosing rich and lean symptoms and tuning the carburetor, take a look at 2-Stroke Jetting Made Easy.