If you have decided to buy your new torque converter for the mini bike or go-kart, you are likely attempting to choose between the 40 and 30 series.

Difference Between 30 And 40 Series Torque Converters:

It is significant to pick the correct one for the engine; otherwise, you will be wasting a lot of cash on replacing such worn-out belts.

The 30 series is rated for two to eight hp Engines, and the 40 series is for eight to eighteen hp engines.

So if you are making use of the unmodified Predator 212 or any other Honda clones with a maximum 6.5hp power or lower, then the 30 series is the right option; if you are making use of a more powerful engine like the Predator 420, then choose the 40 series.

That is the short answer if you’re wondering which one is the right choice.

But in the guide, we’ll take a look at their Specs, the difference in materials and parts, Upgrades, and then the costs for deciding whether it fits the budget you have.


30 Series 40 Series
Recommended Engine 2-8hp 8-18hp
Drive clutch Engagement RPM Drive clutch Engagement RPM 2200 RPM (Can be modified) 1600 (Can be modified)
Speed reduction ratio at high speed 0.9 : 1 or 1.12 : 1 (for 6 inches and 7 inches Driven respectively) 1 : 1 or 1.24 : 1 (for 7 1/2 inches and 8 1/2 inches driven respectively)
Belt Type Asymmetrical Symmetrical
Belt Top Width 3/4″ 7/8″
Speed reduction ratio at low speed 3.13 : 1 or 2.68 : 1 (for 6 inches and 7 inches Driven respectively) 2.43 : 1 or 2.83 : 1 (for 7 1/2 inches and 8 1/2 inches driven respectively)
Driven Unit dia 6 inches or 7 inches 7 1/2 inches or 8 1/2 inches

Driven Unit:

The driven units can have diverse diameters, and you can adjust them to your preference to get lower or higher speed reduction ratios, do remember, though, if you change the driven’s diameter, you will also have to change the belt.

The driver units of the thirty series come for both ¾ inches and one inch crankshaft, and the forty series come for 7/8 inches and 1-inch crankshaft diameter.

Engagement RPM And Driver Unit:

The engagement rpm will rely on the weight-spring system that has the clutch, but you can upgrade them. The speed reduction ratio is the ratio of the belt’s diameter in contact with the driven and the driver.


The belt in the thirty series is asymmetrical, meaning one side is almost flat while the other side has an angle to it, while the forty series belt has symmetry, and both sides are tapered equally.

Major Differences:

In terms of look, the way to distinguish them is from the leaves’ angle, the 40 series will be symmetrical, and the 30 series will be asymmetrical; aside from that, the forty series will be much heavier and have a larger belt. The differences in components are stated below.

Difference In Belt:

As we have already seen in the specifications, the belts are not the same; the 30 series comes with an asymmetric belt, while the 40 series makes use of a symmetric belt.

It’s significant to install the right belt for avoiding excessive belt wear.

Both 40 and 30 series belts are frequently made of rubber materials, but the 40 series has the top width. Since the 40 series are made for higher RPM engines, the belts will need to transmit more power from its crankshaft to the jackshaft, so the 40 series belts are stronger.

Difference In Weight-Springs System In The Clutch:

The main disparity is the kind of weight-spring system they both utilize; the weight-spring system is inside the driver clutch (it’s a component that goes into the crankshaft), which faces the centrifugal force as the clutch rotates with its crankshaft.

The forty series come with rollers and the spring holding all these rollers together; the thirty series has circular springs and circular weights.

The weight and spring can be upgraded for increasing or decreasing the engagement RPM.

For instance, if you desire a better take-off or do wheelies, you can do that by simply making the clutch engage when the engine is producing max torque.

Disparity In Installation:

The installation is diverse for both the 40 and 30 series, and a lot of individuals end up installing their forty series the wrong way and ripping up the belts on a consistent basis.

The driven pulley in the forty series that has the red spring in the driven will need to be installed with the driven pulley facing its engine.

Or, put in simple words, the two movable components of the torque converter will face one another in the forty-series Torque Converter.


Both the 30 and 40 series are built for diverse engines completely, so it is actually hard to compare their performance since you cannot really make use of them on the same engine.

But what if you attempted to compare them in the same engine?

Can You Utilize The 30 Series In A More Powerful Engine?

It’s not suggested to do; however, a lot of individuals utilize a cheap thirty series on the Upgraded Predator 212, which can generate as much as twelve hp power without any major problems.

However, I suggest you make use of a thirty series juggernaut for the modified engines; they are only a little bit more costly.

Ok, It Covers A Small Engine; What About The Big Blocks?

The thirty series comes in for both ¾ inches and 1-inch crankshaft diameter, so it can be utilized on a GX390, 420cc predator, and other such clones by Honda that have a 1-inch crankshaft.

So you can do so if you would want to. But you will likely end up burning through the clutch and belt. Why? The powerful engines will produce more torque, so the parts inside the belt and the clutch itself will experience much more force in the larger engine, causing more deformation.

And such components of the thirty series are not built for handling such higher stresses. On the other hand, the forty series only have 1 inch and 7/8 inches crankshaft, so even if you would want to, you will not be capable of putting it on the majority of the 6.5hp Honda clones without modifying its crankshaft itself.


Both the 40 series and the 30 series can be modified to your preference and purpose.

Modification In The Driver Clutch:

You can change the spring system and weight inside the clutch for increasing/decreasing the RPM at which the clutch actually engages with the belt.

On the whole, the lighter its weight, the higher RPM it’ll need for engaging, and the stiffer its spring, the more RPM it’ll need for engaging.

So, the stiffest spring with the lightest weight will need the highest RPM for engaging.

If you make its clutch engage when your engine is producing the most torque, you acquire a good take-off and can also do wheelies.

Modification In The Driven Pulley:

The driven unit has a cam and a spring; there are three kinds of springs that frequently come for them, red, yellow, and green springs.

Basically, you make the spring stiffer for getting more power out of your engine at a particular speed reduction ratio.

Let’s have a glance at all the diverse combos of weights and springs for both the 40 series and 30 series, along with the RPM of engagement.

30 Series: Diverse Weights And Springs

Spring color Alum-Die Cast (146.8 grams) Zinc Weight (320 gram) Mod-Alum (90 grams)
White 4000 rpm 3100 rpm 4500 rpm
Blue 3300 2200 3700
Purple 3200 2000 3400
Pink 2800 1800 3100
Orange 2300 1500 2500
Black 2100 1400 2300

Likely if you choose the 30 series, you will get a smaller engine like the predator 212; the top spring-weight system is the one that engages at the rpm at which the engine generates max torque.

For instance, predator 212 generates maximum torque of 2500rpm. So the top combo will be ninety-gram weights with the orange spring.

40 Series: Drive Clutch Engagement For Diverse Springs And Rollers

Rollers Yellow Spring Red Spring
Heavy 1600 rpm 2000 rpm
Medium 2200 rpm 2600 rpm
Light 2400 rpm 3100 rpm

Similar to the 212cc engine, the Predator 420 also generates the most torque at 2500 RPM, so the red spring with medium weight will provide you with a good take-off.

Original Vs. Clone:

As you may know already, the original US-made torque converters are gonna charge you double the cash, so are they truly worth it?

In my opinion, the clones function just as fine for the majority of purposes, yes, the original is made of heavier and better materials, but they’re also two to three times the price.

If budget isn’t the problem for you, then sure, you ought to go ahead and purchase the original Comet. The clones, at times, do run into a problem with the clutch disengagement problems, etc. But if you purchase a clone with better ratings, then you will be just fine.


Torque converters are great for off-road go-karts, which need high torque. Both the 30 and series are more similar than they’re diverse; which one is right for you will rely on the engine.

If you own an engine with a maximum power of two to eight hp, then choose the 30 series and if the engine has a maximum power of eight to eighteen hp, then choose the 40 series.

You can modify the weights and springs in the driven and driver to change the engagement RPM for better take-off.