Dyno Testing and comparing the Tillotson 228R Engine

Background of the 228R

EC worked with Tillotson to develop the 225RS engine. During the development, many ideas were not pursued due to cost, time of development, production, and the risk of introducing a new engine and class into karting. 

To minimize risk, we built a contingency allowing us to use the Tillotson 225RS components beyond their spec class. The block with a 72mm or 2.835 bore was the most important, which is still uncommon in today's clone engines. Also, the construction and reinforcement also meant it was better suited for highly modified engines with high compression and rpm. Our goal was to use it for open modified classes and grow that part of the karting market, which has been extremely successful. 

The 228R was the first step to building up the modified market. We want more displacement, closer to 14.5ci, which was a common spec for open classes that restricted the displacement of the engine. Later, the 58mm crankshaft became available, which put them at 236cc or 14.41ci, which was perfect for the class. We also wanted more displacement so our engines didn't get confused with the Tillotson 225RS Spec engine, and it's a good thing because other Tillotson importers started to use the Tillotson 225RS long block and an ARC Flywheel, Stock Coil, and Knock-Off Mikuni carburetors to make a Tillotson 225R. Besides tuning, the Tillotson 228R had 1mm more stroke to give it 4cc+ more displacement (228cc vs. 223.93), which gave it more compression (9.46:1 vs. 9.35:1). 

To produce the Tillotson 228R, we had to make our own connecting rods to connect the Tillotson 72mm piston to the 56mm stroke crankshaft while maintaining zero deck. We also used our SK200 Rev Wheel Flywheel, which has 34° ignition timing vs. 32° ARC and 30° Tillotson/PVL. These are small differences, but they can add up, especially when it comes to tuning.

The Tillotson 225RS originally had an HW diaphragm carburetor. Nearly every carburetor was considered during the development, and even new carburetors were prototyped. However, a slide carburetor would be user-friendly since the Briggs LO206 and World Formula engines used it. Eventually, the HW was too difficult for the average racers since the class was geared towards the entry level and replaced with a 26mm round slide like the knock-off Mikuni. Incidentally, the Tillotson 225RS is more like the 225R. The 228R started with a knock-off Mikuni "VM22." Still, the carburetor wasn't meeting our expectations, so we redesigned and retooled it to make the Wildcat WC22 carburetor, a 26mm slide carburetor similar to the PZ26 but with much-improved tuning and startup. We also made a new intake that would mount the carburetor closer, which helps to prevent the carburetor from hanging outside your mini bike, where it can be knocked off or damaged if the bike is laid down or over the rear tire of your go-kart.

The camshaft for the Tillotson 225RS is a .265 cam based on our original Banzai. The development of the Tillotson 225RS helped popularize the 265 lift camshafts. Since then, many have produced their own versions or copies and used them in performance kits. We use our Banzai in the 228R and in all of our stage 3 kits. 

The cylinder head is also the same for all three of the original engines. The Tillotson 196 foundation was built on the Tillotson JT-207 cylinder head. We were able to update the head to use the same valves as the Predator 212 Non-Hemi, which allowed us to use split-locks with automotive-style retainers on the Tillotson 212R/225RS. The head worked very well, and we used it to make bigger valve heads for modified builds. 

Fast forward four years, and the 228R has been updated with two major changes and one minor change.

First, the minor change is the latest version of the Wildcat WC22. The only change is to improve the cold start further. The overall tune hasn't changed, and it's been the biggest advantage when comparing the performance of each engine. The WC22 is more responsive and pulls much harder on the top end. 

Second, the SK201 is a lighter version of the SK200 flywheel. The SK200, like the ARC equivalents, is designed to meet the minimum weight allowed by NKA, WKA, and ARKA 196cc kart classes. Since we're not restricted by those rule sets with the 228R and other modified builds, we decided to make the flywheel lighter while keeping the fins on it. Less weight reduces the parasitic losses caused by the flywheel to improve the acceleration and responsiveness of the engine. 

Third, the WC946 cylinder head. During the development of the Tillotson 225RS, a big valve head of the stock head was tested. However, with the RS being limited to 6500rpms, the engineers didn't see the need to produce another head. We wanted to redesign the head with a different combustion chamber similar to the difference in the Animal/LO206 heads and the World Formula. Since the Tillotson 225RS would be closer to the World Formula in performance, it would separate itself from the Tillotson 196R and 212R engines. That idea was put on the shelf until now. The WC946 is a head with Stainless 31mm intake and 25mm exhaust valves, 26lb springs, and aluminum retainers. The combustion chamber was reshaped and reduced to 18cc, which bumps compression to 10.92:1, and the spark plug hole was moved to allow larger valves and more flow. The ports were also slightly redesigned with more material around them for improved porting. Not only is it better out of the box, but the potential is much higher. We put a lot of emphasis on value and performance vs. cost of the WC946, which makes it worth it on any build. 

Our 228R MKII with the 26mm slide carburetor and WC946 cylinder head is very close to what could have been the Tillotson 225RS if we had more time and budget. Luckily, over time, we've been able to complete that package. Let's see how its performance compares to the Tillotson 225 engines and some of the similar spec builds using the Predator, Ghost, and Wildcat engines.

Most aftermarket upgrades are identical, but the main differences are engine-based components. We recommend going back through the Road to Horsepower Videos to see how the difference between the based engine affects torque and horsepower. 

Bore vs. Stroke—The 223/224 and 225 are less than .7cc different, but one has 3mm more stroke while the other has 2mm more bore. Most believe that more stroke is for torque and more bore is for the top end. Is this true? And how much difference does it make?

Compression—All of these engines have a range of compression. Consider the difference between the two 223 engines, which have the same bore and stroke but different heads and different compression. 

Cylinder Head – We have three different hemis(Ducar, Wildcat, Predator 212) and two non-hemi(Tillotson 225 and WC946). There are also different valve sizes and valve types in stock(carbon steel) and stainless steel. 

Flywheel/Ignition – The ignition timing and weight of the flywheels vary between models.

Carburetors—Most of the builds have a knock-off version of the VM22, which is really closer to the PZ26 because they are 26mm round slide carburetors. The TM24 flat slide Mikuni and the 26mm round slide carburetor flow nearly the same, around 87-90cfm. Usually, a flat slide will perform a little better, as was seen in Red Beard's Carburetor Shootout. 

Engines

Here are short breakdowns of the engines and the tests. For the Predator 212 Hemi, we included tests with 1.2-ratio rockers and a ported head since this is what it takes to make similar power to the other engines, which also means it adds to the cost of building that engine. 

Predator 212 Hemi – The Predator 212 Hemi used mostly a Go Power Sports Stage 2 "Racer" Kit along with the TM24 Mikuni Carburetor and a thin head gasket to raise the compression in the 4th episode of the road to horsepower. Red Beard previously tested this engine with an original VM22 Mikuni and a Knock-Off VM22, which is a 26mm round slide. The TM24 made the most horsepower from those tests. Later, he would add a 1.2 ratio rocker with a ported head. 

Wildcat Stage 3—The Wildcat 223 made the most power of a stock factory clone engine that isn't a dedicated race engine, i.e., Ghost 212, Tillotson 225RS. The stage 3 kit showed the engine's potential, even more so when the cylinder head was ported. 

Super Ghost 223—The Ghost 212 was stroked to make the displacement of the Wildcat 223 engine, and the same parts were installed as our stage 3 kit, plus stainless steel valves. The engine was very impressive, especially after porting. It also has the lowest compression of all the engines. You have to ask how important compression is.

Tillotson 225R—The previous video tested many versions of the Tillotson 225. Still, the one that can be bought turnkey is the Go Power Sports Tillotson 225R, so that's the most comparable configuration in this test.

Tillotson 228R MKII – We've covered the specs of the 228R, but the other benefit is that the engine is turn-key; add a header, oil, and gas, and get after it. The new 228R comes with 1 liter of Maxima Racing Oil Break-In Oil as part of the package. To break it in, run it under a load for 20-30mins which can be done by riding your kart or mini bike. Drain the oil and use a 20-weight racing oil like our Maxima Racing Oil RS 0W-20 for optimal performance. 

Horsepower:

Predator 212 Hemi—The Predator 212 Hemi made a little more power than the stock-headed Wildcat, but it has a TM24 carburetor and made less than the Super Ghost 223. The power increased when the 1.2 ratio rockers were added, but it still made less horsepower than the Super Ghost. Only when porting and 1.2 ratio rockers are used does the Predator 212 make more horsepower than the Wildcat and Ghost. It goes to show how beneficial porting any head can be. 

Wildcat 223 Stage 3- The flow of the stock head limits the Wildcat 223. However, it picks up extremely well when ported. A ported-head Wildcat makes more horsepower than the Predator 212 with a stock port, 1.2 ratio rockers, and TM24 flat slide carburetors but falls back when the Predator 212 is ported with 1.2 rockers. 

Super Ghost 223- The Super Ghost performed extremely well, with a near-stock head with stainless steel valves and a ported head. The Super Ghost has the lowest compression of the engines tested and only made .04hp less than the Predator 212 with 1.2 ratio rockers(.318 lit) and ported head. Just imagine if you added 1.2 ratio rockers to the Super Ghost.

Tillotson 225R – The biggest problem with the Tillotson 225R is the carburetor tuning. The Knock-Off VM22 is not very good without extensive blueprinting and modifications. The engine has more potential, but the carburetor runs too rich on the top end to make good horsepower. In the last video, we showed the A/F ratio and how the engine performs better with our WC22 carburetor. You would be money ahead to buy the short blocks and add your own flywheel and either our WC22 or a 24mm flat slide carburetor.

Tillotson 228R MKII—The carburetor is tuned very well, but it's the same carburetor as the Super Ghost 223 and Wildcat stage 3. The same goes for the cam and flywheel. So, the biggest advantage of the 228R is the cylinder head. Out of the box, the head flows nearly the same as the other ported heads, especially when you only have a .265 lift cam. There is more in the tank when the head is ported, still with a .265 lift cam. 

Torque:

Predator 212 Hemi- The Predator 212 Hemi is the only engine that is a 212 and lacks the peak torque of the other engines. Outside of the peak numbers, the low-speed numbers are not close to the other engines. What you feel on your butt dyno is going to be the difference in torque more so than horsepower.

Wildcat 223 Stage 3 – The Wildcat 223 is a torque monster. While the Ported Super Ghost 223 made .07ft-lbs more than the ported Wildcat, the Wildcat made all its power lower than the other engines while still putting up good horsepower numbers. The Wildcat will likely feel more powerful because of its low-speed torque. The Wildcat is great for those with heavier vehicles and mud boats that do not turn a lot of rpm but need low torque. 

Super Ghost 223—The Super Ghost 223 is a great balance in peak power and torque. Most of that power is made at a higher rpm than the Wildcat 223, which is due mostly to the difference in the cylinder head and probably the camshaft. If you want more power on top-end, the Super Ghost is a great build. However, the cost of the Super Ghost is the only downside. 

Tillotson 225R—The Tillotson 225 has the same stroke as the Predator 212, so torque between the two engines will be similar but less than that of the 223cc engines with the 58mm stroke crankshaft. Again, carburetor tuning and maybe a little more ignition timing would help make more torque. 

Tillotson 228R—The 228 has the highest compression ratio of all the engines, which should help with its torque. However, it only has a 56mm stroke crankshaft, making it closer to the Predator 212 and Tillotson 225. The good news is that we have clearance 58mm stroke crankshafts and rods for the 225/228 engines, which will make them 236cc engines. 

We've averaged the horsepower and torque of each engine to give you an idea of its overall performance. However, you have to consider each engine's complexity. The Predator 212 can hold its own, but it requires more components to do so. The Super Ghost 223 is a great performer, but it requires the most work and is the most expensive. The Tillotson's are turn-key and don't have to be built at all. 

So far, the Wildcat 223 seems to be the best engine when it comes to cost. Unlike the Super Ghost, which needs to be stroked, the Wildcat is already 223cc and only needs our stage 3 kit. You can buy parts individually, or you can opt for a flat slide carburetor, which will help make a little more power. Porting is the key to unlocking the performance of any of these engines, which makes the Wildcat hard to beat for the price.

The Tillotson 228R is the best engine without porting. The 1mm extra stroke over the Predator 212 and Tillotson 225 helps make a little more torque, and the cylinder head helps to make a little more top-end power. While the Wildcat is arguably the best value at the moment, the Tillotson 228R is turnkey and doesn't require governor removal, cam/crankshaft clearancing, or other modifications. That said, there are ways you can improve the performance of the Tillotson 228R. 

Recommended Build for the 228R

*Note – The Tillotson 228R will now come with a Torch K7RTI Fine Wire Iridium spark plug picking up .2-.3hp. The spark plug is a fairly inexpensive upgrade to any engine listed.

1. Port the head – the two biggest gains from any engine are from the carburetor and porting the cylinder head, which is because of increased airflow. The gains will come from the head since we already have a 26mm carburetor. These engines suffer from airflow restrictions, which hinder modifications like camshafts and ratio rockers. Before you add more cam or rockers, have the head ported first. For reference, the Wildcat WC946 head can reach 80-85cfm at a .250 lift when ported, so there is a lot of potential left even with the .265 lift cam. The head can reach 95-100cfm by .350 lift for those wanting to add more camshaft later. 

2. Stroke the engine – The 228R is a good overall engine, but its torque can improve, especially at lower rpms with a 58mm crankshaft. Having more low-end torque will make the engine feel much stronger on your butt dyno. You can order a pre-clearance 58mm crank, 8279 rod, and the 72mm piston that comes in the 228R to make 236cc

3. 24mm Flat Slide (Optional) —For those who want more bolt-on power without getting back into the engine, our PWK24 kit will improve performance over the round slide carburetor. The change may be small compared to the previous modification, and to some, the cost of a different carburetor may not be the route they want to go. You also need to consider that the flat slide is spigot-mounted and will stick out further.

4. SK300 PVL Flywheel & Ignition (Optional) – The flywheel and ignition is another simple external modification. The PVL retards ignition timing below 1800rpms to allow the engine to pull start with far less kickback. The compression is high on the 228 and even higher when we stroke it to 236cc (11.28:1). The engine will be harder to pull start and want to kick back harder. The flywheel and ignition are fairly expensive, and other than a startup, they will offer very little change in performance.

5. Camshaft & Valve Train – The reason we save the camshaft for last is due to the many changes in the valve train to support bigger camshafts:

- Dual Valve Springs & Retainers

- Billet Roller Rockers

- Chromoly Push Rods

- Longer Valve (Depending on how much lift)

- Spring Pockets Cut

These components are linked to one another to best support and stabilize the valve train. Any compromise head can cause premature component wear and/or failure. Most of the engine cost comes from these components and the labor to fit them into your engine. As we've seen in another video, especially the Predator 212 Road to horsepower, the ports limit the gains of a bigger cam and roller rockers. If the head isn't ported, it's a lot of money for little gain. You can follow this method to build almost any mini bike or go-kart engine. 

Trouble Shooting Fuel Issues:

In the video, the 228R MKII ran flawlessly on the dyno but had some issues when installed on the bike. We wanted full transparency because hiding a problem doesn't help our customers since we can't account for every variable when the engine is installed. We insisted that Red Beard leave those problems in the video so we can resolve them with our information. We're going through the same troubleshooting advice we gave Red Beard because the issue isn't the engine or the tuning, but it can be a common problem for anyone running a similar engine with a similar fuel system. 

Check your fuel tank - Ensure there is at least a 1/4 vent, and the hose is unobstructed. A vent that isn't large enough will cause the carburetor to run lean; the longer the engine runs, the worse it will get. If it's blocked, it can cause a rev-limiting effect where the engine will not turn up past a particular rpm. Lack of venting is the number one problem concerning carburetor tuning and engine problems. 

Gravity feed - Since the engine was being gravity-fed to the fuel pump, it's possible the fuel pressure(we don't have fuel pressure regulators on these engines) overridden the carburetor's inlet needle. Over 20 years ago, lead was removed from the polymers that make up the inlet needles, which made them less resistant to solvents and fuels. These inlet needles do not seal as well as they did 20-plus years ago. So, depending on the fuel pressure and the fuel passing the inlet needle, the carburetor will run richer. You'll sometimes see a lot of extra fuel from the bowl vents. Adding recirculation doesn't help fix the tuning issues. Instead, we told Red Beard to remove the fuel pump from the fuel system and straight gravity feed the engine. The drawback is a change from a pump system to a gravity feed, which may require a jet change. Going up to a 110 or 115 main jet in the WC22 should be enough to take care of the hesitation caused by removing the fuel tank. 

When using a gravity-fed system, the more fuel volume you have(gasoline weighs about 6.1lb per gallon), and the higher the tank is above the carburetor, the more the fuel pressure will increase. 

Fuel Line—Use good-quality fuel lines. We've had issues in the past using the black rubber fuel lines, as they break down quickly, and debris can cause the inlet needle and seat to leak. 

Run fresh gas—Bad or stale gas can cause engine issues. Gas is a solvent, and over time, the rubbers and polymers in the fuel lines or fuel system can break down and saturate the fuel. While it's not as bad as alcohol fuels(methanol and ethanol), gas does capture moisture, and water doesn't make a good fuel.