Tillotson 225 vs 236 vs Wildcat 240: Which Engine Setup Makes the Most Power?

Updating the Tillotson 225 and Billet Cylinder Head for Performance

In a recent video, Red Beard revisits testing of the MoFlow billet cylinder head, this time evaluating how the engine responds to increased displacement along with updated valvetrain components. This includes a different camshaft and rocker arm combination, both critical factors in maximizing small engine performance for kart racing and mini bike applications.

In the original test, Red Beard used the Tillotson 225 platform. At the time, this engine was considered a major upgrade over the common 212cc clone engines used in kart racing and mini bikes. The Tillotson 225 gained popularity due to its strong value, featuring a factory billet connecting rod and a lightweight, racing-style piston—components that made it ideal for performance builds right out of the box.

Since then, many builders have pushed the platform further by increasing displacement to 236cc. This configuration has become a common and affordable setup in the 14.5ci open class in kart racing, offering a noticeable gain in torque and horsepower while maintaining reliability when properly assembled.

For the original test, Red Beard used the Tillotson 225-based platform to dyno the MoFlow billet cylinder head, which features a 32mm intake valve and a 25mm exhaust valve. The setup included Gage 1.3 ratio roller rockers paired with a 356 camshaft, resulting in a total valve lift of .462”.

While the engine produced strong power numbers, it encountered valve float just above 7,000 RPM. Further inspection revealed that the issue was caused by interference between the Gage roller rockers and the valve retainers—a critical clearance issue that limited high-RPM stability.

This serves as an important reminder for anyone building performance small engines for kart racing or mini bikes: most aftermarket components are not truly “plug and play.” Proper setup, measurement, and clearance checks are essential to prevent performance loss—or worse, catastrophic damage to expensive engine components.

Updating to the Tillotson 236cc: Camshaft and Valvetrain Changes

In the updated test video, the entire engine combination has been revised. The platform is now based on a Tillotson 236cc engine, increasing overall displacement, piston speed, and compression compared to the earlier 225 setup. These changes alone significantly impact torque production and overall small engine performance, especially in kart racing and mini bike applications.

The valvetrain has also been reconfigured. The billet cylinder head is now paired with EC 1.4 ratio Rev roller rockers and a .308 camshaft, resulting in a total valve lift of .431”. Compared to the previous .356 camshaft (.462” total lift), the .308 features reduced duration and less overlap.

This change was intentional—aimed at creating a more street-friendly power curve. By reducing duration and overlap, the engine benefits from improved idle quality, stronger low-end torque, and better throttle response, which are all critical for mini bike performance and recreational riding applications.

The .308 camshaft has become a staple in the small engine performance world. It is one of the most widely used, tested, and documented camshafts available today. Popularized across multiple builds, it has been featured extensively by Red Beard’s Garage on projects such as the “Road to Horsepower” Predator 212, Predator 224, and now the Tillotson 236.

Using the same camshaft across different engine platforms provides valuable insight into how a single component performs under varying conditions. In this case, the .308 cam helps highlight how camshaft selection influences power delivery, rideability, and overall engine behavior across multiple displacements and combinations.

Overall, the updated 236cc combination performed well, particularly in improving low- to mid-range power characteristics.

Comparing Three Engine Setups: Budget vs Billet Performance

Before directly comparing the Tillotson 225 and Tillotson 236 billet head combinations, it’s important to introduce a third engine into the discussion—the Wildcat 240 Stage 4 build.

The Wildcat 240 represents a budget-friendly performance engine, designed for riders who want solid gains without stepping into a full billet setup. Unlike the Tillotson builds, this engine uses a cast cylinder head along with more basic valvetrain components, including stock push rods and 26 lb single valve springs. It also runs a smaller 24mm carburetor and a milder .268” camshaft.

By comparing all three engines, we can better understand the performance differences between a budget-oriented build and more advanced billet cylinder head combinations used in kart racing and mini bikes.

Engine Specification Comparison

How Does the Tillotson 236 Compare to the Original 225 Test?

When comparing the original Tillotson 225 billet head test to the updated Tillotson 236 combination, the peak numbers alone can be misleading.

Original Tillotson 225 Billet Head

• Peak Torque: 15.5 lb-ft @ 7,100 RPM
• Peak Horsepower: 21.23 HP @ 7,200 RPM

Note: Estimated 22–23 HP without valve float limitations

Updated Tillotson 236 Billet Head

• Peak Torque: 15.7 lb-ft @ 5,800 RPM
• Peak Horsepower: 19.57 HP @ 6,900 RPM

Peak Numbers vs Real-World Performance

At first glance, the 225cc engine appears to outperform the 236cc. It produces slightly less peak torque (only 0.2 lb-ft difference) but delivers approximately 1.6 more horsepower at a higher RPM.

However, peak numbers don’t tell the full story.

When analyzing the entire power curve, the 236cc engine produces more torque—and therefore more usable power—from the start of the pull up to approximately 6,500–6,600 RPM. After that point, the 236 begins to fall off, while the 225 continues to pull stronger into higher RPM ranges

Tillotson 225: Horsepower/Torque - Tillotson 236: Horsepower/Torque - Wildcat 240 Stage 4: Horsepower/Torque

Why the Power Curves Are Different

The primary reason for this difference comes down to camshaft profile and overall engine combination.

The 225cc engine used a larger camshaft (.356 with .462” total lift) and 1.3 ratio rockers. This combination provides:

• More valve lift
• Increased duration
• Greater overlap

These characteristics improve airflow at higher RPM, allowing the engine to “breathe” better as RPM increases. However, they are less effective at lower RPM, where airflow velocity is lower.

Because the 225cc engine has a shorter stroke, it relies more heavily on RPM to achieve higher mean piston speed and improved volumetric efficiency. Around 7,000 RPM (roughly 2,500 feet per minute piston speed), airflow through the head, cam, and valvetrain becomes highly efficient—this is where the engine really comes alive.

On the other hand, the 236cc engine benefits from:

• Increased displacement
• Higher compression
• Greater piston speed at the same RPM

These factors allow the engine to generate stronger cylinder fill earlier in the RPM range.

Combined with the .308 camshaft (.431” lift) and 1.4 ratio rockers, which feature less duration and overlap, the result is:

• Stronger low- and mid-range torque
• Improved throttle response
• Earlier peak torque

This is why the 236cc engine outperforms the 225cc from the beginning of the run up to the mid-range, making it ideal for mini bikes, recreational riding, and kart racing applications that require a broad powerband.

Choosing the Right Setup: High RPM vs Broad Powerband

This comparison highlights a key trade-off in small engine performance:

Tillotson 225 Setup (.356 cam)

• Better for high-RPM racing applications
• Strong top-end horsepower
• Requires higher engagement RPM (clutch or stall)
• Increased stress on valvetrain components

Tillotson 236 Setup (.308 cam)

• Stronger low- and mid-range torque
• More usable, “street-friendly” power delivery
• Better suited for mini bikes and recreational builds
• Broader, more forgiving powerband

Reliability Considerations

Engines designed to make peak power at higher RPM inherently place more stress on internal components—especially the valvetrain. Increased spring pressure, higher lift, and sustained RPM can lead to accelerated wear or failure if not properly supported.

For builds similar to the high-RPM 225cc setup, pushrod selection becomes critical. We recommend upgrading to 1/4” or 5/16” push rods instead of 3/16” chromoly push rods. The larger diameter helps reduce deflection under load, improving valvetrain stability and minimizing the risk of valve float or component failure.

How Does the Wildcat 240 Compare to the Tillotson Billet Head Engines?

Both Tillotson engines used the same billet cylinder head but produced two very different results due to camshaft and valvetrain changes. That raises an important question:

How do these high-end billet combinations compare to a more budget-friendly Wildcat 240 build?

Cost vs Performance: The Real Difference

Before working with Red Beard’s Garage, our goal has always been to develop engine combinations that deliver the best possible performance at the lowest cost, without sacrificing durability. That philosophy started with the Tillotson platforms and continues with the Wildcat series.

One of the biggest barriers for most builders is the cost of a billet cylinder head setup.

A typical MoFlow billet head combination includes:

• Billet cylinder head: $650
• Intake: $75
• Valve cover: $90
• Chromoly pushrods: $30
• Roller rockers: $200

That puts the total at $1,045 before even adding a camshaft, carburetor, or short block.

And that’s just the beginning.

As we’ve discussed in previous builds, once you move into larger camshafts, you also introduce:

• Dual valve springs (requiring proper install height setup)
• Stronger billet rocker arms
• Additional head modifications
• Potential port work and larger valves

These upgrades quickly compound the total cost of a high-RPM performance engine.

The Wildcat 240 Approach: Smarter Performance Gains

Instead of chasing peak numbers with expensive components, we took a different approach with the Wildcat 240 platform—focusing on efficient power gains using simpler, more affordable parts.

The Wildcat 240 Stage 4 build includes:

• Reaper camshaft
• Billet flywheel
• WC200 72mm forged piston with long rod
• CNC-ported WC946-3 cast cylinder head
• PWK24 carburetor

This complete setup comes in at around $1,200 total, which is nearly the same cost as just the billet head setup and valvetrain components used on the Tillotson 236.

Wildcat 240 Performance Numbers

• Peak Torque: 15.71 lb-ft @ 5,400 RPM
• Peak Horsepower: 18.49 HP @ 7,100 RPM
• Head-to-Head Performance Comparison

What makes these results impressive is how closely the Wildcat 240 competes with the billet head engines:

• The Wildcat 240 produces virtually identical peak torque to the Tillotson 236 (15.7 lb-ft), but reaches it 400 RPM sooner, improving low-end responsiveness.
• Peak horsepower is only about 1 HP lower than the 236, and occurs at a very similar RPM.
• Compared to the Tillotson 225 billet head setup, the Wildcat 240 actually produces more torque and power throughout most of the curve up to approximately 6,400 RPM.
• What This Means for Real-World Performance

This comparison highlights a critical takeaway in small engine performance:

You don’t need a billet head to make strong, usable power.

The Wildcat 240 delivers:

• Strong low- and mid-range torque
• Competitive peak performance
• Earlier power delivery
• Lower overall cost

This makes it an excellent choice for:

Mini bikes

• Recreational kart racing
• Builders looking for maximum value per dollar
• Billet vs Budget: Choosing the Right Setup

Tillotson Billet Head Builds

• Higher peak horsepower potential
• Better for high-RPM racing applications
• More expensive and complex
• Requires precise setup and supporting components

Wildcat 240 Stage 4

• Nearly identical torque with earlier delivery
• Strong overall power curve
• Much lower cost of entry
• Simpler, more reliable component combination

While billet cylinder heads and aggressive camshafts can deliver impressive top-end numbers, the Wildcat 240 proves that a well-designed combination of affordable components can achieve comparable real-world performance—especially where it matters most.

For the average rider or builder focused on mini bike performance, kart racing, and small engine reliability, the Wildcat 240 offers one of the best value-to-performance ratios available today.

Performance Comes Down to Application

The performance of these engines ultimately comes down to how and where the power is used.

Most recreational mini bike and kart builds rely on clutches or CVT systems that engage around 2,500–3,000 RPM. While dyno pulls typically begin recording around 3,300 RPM—and become more consistent above 3,500 RPM—this lower RPM range is critical for real-world drivability.

At 3,300 RPM, the differences between these engines are significant:

Tillotson 225 Billet Head

• 6.41 lb-ft torque
• 4.07 HP

*Note: weaker than even a stock Ghost 212 until ~4,200 RPM

Tillotson 236 Billet Head

• 8.76 lb-ft torque
• 5.55 HP

Wildcat 240 Stage 4

• 8.68 lb-ft torque
• 5.92 HP

Low-End Response vs Top-End Power

At lower engagement RPM, the Wildcat 240 clearly stands out. It delivers stronger, more immediate torque, making it noticeably more responsive off the line—an important factor for mini bikes and recreational kart setups.

As RPM increases, the gap begins to narrow:

• The Wildcat maintains a performance advantage up to approximately 6,500 RPM
• Beyond that point, the Tillotson 236 begins to edge ahead slightly
• At higher RPM (approaching 7,000+), the Tillotson 225 becomes the stronger performer due to its more aggressive camshaft and high-RPM efficiency

Racing vs Recreational Setups

In racing applications, clutches are typically set much closer to peak torque—often engaging around 5,000–5,500 RPM or higher.

In this scenario:

• The Wildcat’s low-end advantage becomes less relevant
• The Tillotson 236 offers a slight torque advantage through the mid-range
• The Tillotson 225 ultimately dominates at higher RPM due to superior airflow and camshaft characteristics

This highlights an important principle:

Engine setup is just as important as peak power when matching a build to its application.

Cast Head vs Billet Head Performance

One of the most interesting takeaways from this comparison is how well a cast cylinder head with a mild camshaft can perform when properly matched.

The Wildcat 240 proves that:

• A well-designed cast head
• Moderate lift and duration
• Proper component matching

…can deliver strong, competitive performance without the cost and complexity of a billet setup.

Where Billet Heads Make the Difference

The true advantage of a billet cylinder head comes into play in high-performance and racing environments.

Billet heads are designed to:

• Support higher valve lift
• Handle increased spring pressure
• Provide improved port geometry unrestricted by factory limitations

However, these advantages are only fully realized when paired with:

• Larger camshafts
• Higher RPM operation
• Supporting valvetrain components

Understanding Camshaft and Airflow Differences

At first glance, the difference between the two billet setups may seem small:

• .308 cam with 1.4 rockers
• .356 cam with 1.3 rockers

This results in roughly:

• ~.030” additional lift
• ~10° more duration

But when lift and duration are combined, they significantly increase the total valve event area—which directly impacts airflow. More area under the curve = Greater average airflow ? More high-RPM power

By comparison, the Wildcat 240 operates with:

• Significantly less lift (.163”–.194” less)
• Less duration

Yet it still performs competitively due to its efficient combination and stronger low- to mid-range power delivery.

The Trade-Off: Powerband vs Peak Power

Both the Tillotson 236 and Wildcat 240 could gain more top-end performance with increased camshaft duration. However, this would likely come at the cost of:

• Reduced low-speed torque
• Less responsive throttle behavior
• Narrower powerband

This reinforces the core theme of this comparison:

There is no “best” setup—only the best setup for your application.

Final Thoughts

The Road to Horsepower series continues to provide valuable insight into how different engine combinations perform under real-world conditions. As more dyno testing is completed, these comparisons will help builders make more informed decisions based on their specific needs—whether that’s kart racing, mini bike performance, or a balanced recreational build.

FAQ:

What is the difference between the Tillotson 225 and 236 engines?

The main difference is displacement and power delivery. The 236cc engine produces more low- and mid-range torque due to increased stroke and compression, while the 225cc engine performs better at higher RPM with a more aggressive camshaft.

Is a billet cylinder head worth it for mini bikes?

A billet cylinder head is worth it for high-performance or racing builds where higher RPM, more lift, and increased airflow are needed. However, for most recreational mini bike setups, a well-built cast head can provide similar real-world performance at a much lower cost.

Which engine is best for a mini bike: Tillotson 236 or Wildcat 240?

The Wildcat 240 is often the better choice for mini bikes due to its strong low-end torque, affordability, and broad powerband. The Tillotson 236 is better suited for more aggressive builds that require higher RPM performance.

Why does camshaft selection matter in small engines?

Camshaft selection determines valve timing, lift, and duration, which directly affects where the engine makes power. Smaller cams improve low-end torque and drivability, while larger cams increase high-RPM horsepower.

What makes more power: billet head or cast head?

A billet head has more potential for peak power due to better airflow and the ability to handle larger camshafts. However, a cast head can produce comparable usable power when paired with the right components, especially in lower RPM applications.

Why is low-end torque important for mini bikes?

Mini bikes typically use clutches or CVTs that engage at lower RPM. Strong low-end torque improves acceleration, throttle response, and overall rideability in real-world conditions.