Introducing the Wildcat 240RS Engine

The Wildcat 240R is the culmination of the last decade of small engine evolution, performance, and development. We've taken the most popular parts combinations while including some of our latest performance parts to build the best platform for your mini bike or racing go-kart. We aim to create an out-of-the-box engine with equal or better performance than engines that cost much more. 

Wildcat 240RS Development:

For over 55 years, we have been expertly tuning race machines and have made many innovations. Since 2015, we have been working on engine development for kart racing, starting with our work with Tillotson Racing to produce their R-Series based on the very popular Honda GX200 and its many iterations of clones. The Honda-based Clone platform has been tremendously successful due to its low cost and accessibility. The aftermarket has fully taken advantage of its popularity, which has only grown since the introduction of the Tillotson R-Series block. Since then, other Clones have made advancements with stronger blocks and improved capabilities. To stay ahead of the curve, we're using many of the latest factory components from the Predator, Wildcat, Tillotson, Ducar, and Ghost engines, along with many exclusive components we've developed. 

Below, we explain all the key components and features and why they were involved in the development of the Wildcat 240RS engine. 

Wildcat 72mm(Bore) x 59mm(Stroke)

There is no replacement for displacement. The Wildcat block is well reinforced, similar to the Tillotson R-Series engines. The 72mm bore increases the displacement over the 70mm and also gives you more options for piston and rod combinations. You can use the factory flat-top piston, the Tillotson 72mm, or our newest EC Forged 72mm pistons, which have coated skirts with oversizes available. 

To further enhance our engine, we are using the 59mm stroke crankshaft, which means 5mm more than the 196cc, 4mm more than the 212 and Tillotson 225, 3mm more than our 228R, and 1mm more than the 223/224, and 236cc engines. More crankshaft stroke has many performance benefits, from mechanical leverage to piston speed. 

The increase in displacement will further increase compression. In previous years, builders and racers struggled to get compression out of their engines using small combustion chamber factory heads or having them welded up, which is very expensive. These heads were very limited in what they offered in performance and reliability. You would also need to run a thinner head gasket that may not seal well and find the correct piston and rod combination to raise the engine's compression. Out of the box, this engine is approximately 11:1 with the piston being about .010 in the hole and using a .045-.048 head gasket, leaving room for more, but we recommend keeping around 11:1 for any pump gas build(91 or 93 recommended).

WC22 26mm Round Slide Carburetor:

One of the most popular upgrades to an engine is replacing the lethargic emission-regulated carburetor with a better-flowing and better-tuned carburetor. The most popular, of course, has been the very inexpensive Knock-Off "VM22" carburetors based on the PZ26. Similar carburetors have been used on the Tillotson 225RS, our 228R, and Briggs World Formula, and standardized by countless daily builds. We've proven to have the best-tuned version straight out of the box and include a short intake to move the carburetor closer to the engine for better fitment on most mini bikes and go-karts. The intake is designed to port match the WC946 cylinder head with a slightly larger inlet. 

WC946 18cc 31/25mm Cylinder Head

It's common knowledge power comes from the head, and for any engine to be successful, it's largely dictated by how well the head performs. Common questions from the style or type of head, like the hemi vs non-hemi, are what size valves and what size combustion chamber. We develop the Wildcat Non-Hemi WC946 to enhance any engine with high-performance builds and modifications in mind. The intake valve is larger than any other factory's small block head, and both valves are stainless. Compression is a high focus of many, so to increase compression on any engine, the combustion chamber is 18cc vs the more common 22cc heads. The spark plug location was moved to allow bigger valves in the future, and the ports were enlarged with more material around them to push the head further than any factory head. Not only do you get a good head out of the box, but you also get one with the most potential when modified. To get the most from this package, porting the head will significantly improve the performance of the engine. The head comes with 26 lb springs and billet aluminum retainers. 

Banzai .265 Cam (224 version)

The Banzai changed the narrative when it came to "what camshaft to choose for the mini bike or mild go-kart engine build." The market primarily used the Mod2 or similar camshafts with a stock lift of around .225 and a duration of around 245 degrees. We used those cams for the "cheater" or builder-prepared classes, which only had lift checks and no duration checks. While they gave an advantage to those classes, the .265 cams were better suited for a bigger and broader power band, which is why we used them in developing the Tillotson 225RS. Since the introduction of the Tillotson 225 and Banzai, the market has adapted these camshafts under private labels under various names. Now that camshaft is included directly from the factory, and most importantly, this version is designed around the longer stroke 58mm and 59mm crankshafts, so you don't have to worry about clearance-ing the cam. 

Cast Aluminum Flywheel

The cast aluminum flywheel is not commonly used on stock engines. Only a few kart shops have offered engines with the cast aluminum flywheel, and we also spec the Tillotson 212R with one. The cast aluminum flywheel is lighter and more reliable, with a higher rpm rating. The magnets are cast into the aluminum, unlike the cast iron, which is glued on with a single bolt holding it to the flywheel. The aluminum flywheel also has the fins cast in rather than the fragile plastic fins. The benefits of these flywheels have been a cost-effective alternative to the billet aluminum flywheels used on the market, which is why they are included on the Wildcat 240.

Governor/Ignition Coil

The Wildcat 240 doesn't have an internal governor. The internal governor is often a hassle for those modifying their engines. Governors have frequently been modified to raise the engine's rpm limits, whether to comply with rules or to get more speed out of the engine. We had a specially modified governor designed for the Tillotson 212R that would allow the engine to turn as high as 6000rpms, which was cost-effective. However, you still had the issue of removing the governor and plugging the block if you wanted to build the engine fully. Instead, we use the same coil as the Ghost 212 to rev limit the engine to 6100-6200rpms. Rev liming coils have been used on the Briggs LO206, & World Formula, the Tillotson 212RS & 225RS engines, the Ghost 212, and the latest Ducar 212. The growing rev limiting trend is to help regulate classes to make them easier to tech and reduce "cheating." 

Using a coil to limit the rpms also reduces much of the labor required to build this engine. If you upgrade to a non-rev limited coil, we highly recommend our 8270 forged/billet connecting rod to handle the higher rpms. With these modifications, the engine should handle 8000 rpms without valve float. Changing to a non-rev limited coil will also increase the horsepower across the entire powerband, with about 10% more at peak.

Sparkplug

We have found that fine-wire iridium plugs improve engine performance over other plugs. In testing, we're seeing about .2-.3hp in power over most plugs, but most importantly, we're seeing more consistent O2 readings, which means carburetor tuning and performance will be more consistent. 

Many have used the Autolite 3910X as the plug of choice, and some claim power advantages by increasing compression by about .2-.25:1. Since we're at a higher compression ratio to start, those advantages are far less significant. The AR3910X plugs are often in too cold of a heat range to keep the plug clean. Not only are the advantages lost, but it can cause a more significant loss in performance when the plug is too dirty to fire appropriately. We find this most problematic with the box stock classes that run rich at low speeds and idle but have also been. The Torch K7RTI is the ideal heat range to keep the plug clean while offering performance advantages. 

Side Cover

The side cover has an oil-fill hole in the top, which has many advantages. The first is obvious: the ability to add oil to your crankcase from the top of the engine rather than the sides. While the intake manifold has a pulse fitting for the fuel pump, it's possible to get a vacuum from the crankcase instead. You can use our 280 PCV to vent the crankcase to your oil catch can. The pressure control valve(PCV) is used to control crankcase pressure with a one-way valve that allows positive pressure to come out of the bottom end in an attempt to create negative pressure, which can help the ring seal. The PCV isn't included but is sold separately.

Top Plate and Fuel Pump

Since stock fuel tanks are often replaced by top plates and linkages for aftermarket carburetors and remote tanks and fuel pumps feed the carburetor, we omitted them from the engine. Usually, top plates are designed to include a linkage for stock-style carburetors, making them look bulky and unnecessary for most aftermarket carburetors. Instead, you get a nice low-profile top plate like the one that comes on the Ghost 212 and an aluminum fuel pump. We want the engine to look good and be as turn-key as possible.

Cost and Value

Cost is one of the biggest concerns with most, if not all, customers. In many cases, starting with the least expensive platform gives you a little more to spend modifying the engine, which could make the engine more powerful dollar for dollar. So we've broken down the cost of the Wildcat 240 in a few different ways: The retail price of every individual part used to build the engine and a cost comparison of a competitor's engine if you were to buy many of the individual aftermarket performance parts.

Retail cost for every individual part.

It's hard to say if anyone has broken down the cost of every part, bolt, and gasket that makes up any of these small engines into the individual retail pricing. What you find is the complete engine costs far less than if you bought all the individual pieces. While it may not seem surprising, the price difference is more significant than most realize. When you buy the engine, you save a lot more money than you think. 

Cost Comparison

The Predator 212's relentless popularity is due to its low prices and accessibility. There are many other engines that are better quality and offer more performance advantages, including their Predator 224 Non-Hemi, especially when it gives you more options for upgrades. For most builds using kits like our stages 1, 2 & 3, the engine's cost may not be justified by the difference in performance from one engine to the next, as we've seen on Red Beard's Road to Horsepower. We aim to widen the performance gap while making the engine competitively priced.

We've broken down costs in various ways with different engines:

First, by the bolt-on parts that would be aftermarket to the other engines (carb, flywheel, head, cam, etc.); in many cases, building another engine using the same parts is more expensive. This list is incomplete, as in the case of the Hemi engines; you'll also need to buy additional valve train components, from rocker arms to push rods, to make the conversion to the non-hemi WC946 head. 

Second, we add the cost of a 59mm crankshaft. This will cause you to use a billet rod in most cases, which the Wildcat 240RS doesn't have. However, it's necessary if you want to use a 59mm crankshaft in most engines. In some cases, like the Predator 212 Hemi, fitting the 59mm crankshaft may not be possible. Using the 59mm crankshaft with a 70mm bore is 227.06ccc, so you would still have much less displacement than using the 72mm bore. 

Lastly, it includes a 72mm bore block to match the displacement of the Wildcat 240RS engine. At this point, the only parts you are reusing are blower housing, recoils, and some hardware. In some cases, you may need additional gaskets and bearings, so the overall cost will vary. We also make a point to mention labor is an extra cost. Even for those capable of building the engine themselves, you are using your time to build a similar engine. Consider also how much time is saved buying the Wildcat 240 as your platform for modifications.

The Wildcat 240RS is so valuable that it can be stripped, and parts can be sold or repurposed for other builds. Usually, when a part gets replaced on a Predator or clone, the parts have very low to no resale value. In other words, removing the cast iron flywheel, stock carburetor, or stock camshaft from the engine is practically worthless. However, the Wildcat 240 camshaft, flywheel, and other parts can be reused or sold to pay for the Wildcat's next modifications. Even if you decide to use a modified cast head or a billet head on this Wildcat, the WC946 cylinder head is worth 164.99. 

We are excited to offer the next generation of clone racing engines, the Wildcat 240RS engine.