30 or 40 series Torque converter/CVTs are often used in Go-Kart and Minibikes for power transmission from the engine to the wheels, if you have one of these in your setup it’s very likely that you would have run across some problem.
Most of the problems are usually due to the wrong selection of belts and unaligned pulleys. We will look through some of the common problems in this article.
Torque converter belt slipping
- Wrong Belt size and/or symmetry
- Pulleys not alligned
- Drive/Driven parts worn out
First and foremost, you need to check whether the belt you’re using is the correct belt for your setup, this guide goes into details about how to pick the right belt for your setup. If you have a symmetric belt in a 30 series, for example, that will cause problems.
It’s a good idea to check whether the belt you have is the correct belt, most problems you face will likely be due to using the wrong belt in your setup.
Now once you’re sure that your belt is the correct belt, next check whether you have installed the torque converter correctly, and the driver and driven pulleys are aligned properly (you can find lots of youtube videos on how to install your version of the torque converter, setup can be different for different series, for example, 30 series setup is a bit different from 40 series)
If it all checks out, then the problem is either the parts inside the torque converter or your Gear ratio (axle sprocket: CVT sprocket) is too high.
Check whether the driver or driven parts are worn out at the surface which holds the belt, the slip is likely caused by those wears. In such situations, you will have to replace those parts if the damage is too heavy.
Go kart torque converter jerking
It often happens that you experience a jerk when you accelerate the torque converter from 0.
Check the belt size chart and make sure you are using the correct belt. If the belt size is correct then take off your driver unit to clean it and lubricate it.
Make sure the throttle cable is properly installed, lubricate the drive chain after every few rides. Replace the chain if it’s worn out
Check if the engine is working properly.
Torque converter sticking
Took your foot off the gas but the clutch never disengaged? Many people have this problem with the series 40, you take the foot off the gas and expect the pulleys to go back to their idle position, but they get stuck.
In the 40 series, these jams happens usually due to the spring-weight system not being able to move easily, so you’ll need to take your clutch apart and clean and lubricate the inside parts of the movable clutch (make sure not to add any lubrication to the parts in contact with the belt, that will ruin your torque converter).
If even after cleaning and proper greasing the problem continues, it’s likely due to your torque converter not being of good quality, or the outer part of the clutch might be too big making it hard to slide back. In such cases, unfortunately, the best solution is to get a new good quality torque converter.
Driven pulley/Go-kart moving at idle
Your go-kart should not be moving at idle, otherwise, it will take off as soon as you start the engine, any engine comes with a pre-set idle rpm which can be adjusted. If the driven clutch is starting to engage at the idle rpm, then your idle speed is too high for your weight-spring system in the clutch.
If the clutch is not engaging but the Kart is still moving, it’s likely a belt issue, i.e. you have a tighter belt than the one required for your set-up.
If the clutch is engaging, you have 2 options:
- Decrease the idle speed of the engine, there are idle screws in the engines and if you loosen it, the idle speed will decrease.
- Change the weigth-spring system in your clutch, a stiffer spring with lighter weight will increase the engagement rpm
If the issue is not related to clutch engagement, then check whether you’re using the correct size belt or not, more likely you have a tighter belt that is pulling the driven at idle.
Belt wearing issues
The most common issue, belt getting worn out. Common reasons:
- Bad Gear ratio (sprocket in axle : sprocket in Torque converter) with large tires. 6:1 is a good, common ratio for a 15″ rear tire, larger tires and high ratio will cause problems
- Torque converter not properly installed
- Drive and driven pulleys not alligned
- Use of wrong belt length for your torque converter (most common)
- Bad quality belt
- Slippage due to wear in metals (covered earlier on in the article)
Make sure your torque converter is installed properly if the belt is asymmetric then the tapered side will be towards the clutch and the non-tappered side will be towards the engine.
Make sure you are not putting too much load on the go-kart unless your gear ratio is adjusted accordingly, by the load I mean climbing the hills, or pulling a heavy load, these actions require high torque.
Check the pulley alignment. Choose the right belt length. Clean and lubricate the torque converter in regular intervals.
These are the most common problems in the torque converter, usually, the solution lies with the belt size and proper installation, and time to time maintenance. Sometimes, your torque converter itself could be of low quality, check our list for the best 30 series torque converters.
But of course, I know every setup is different and you might come across a problem very unique to you, I suggest you learn how the torque converter works and you might be able to find the solution yourself.
Other than that, there are a few active go-kart forums, very likely the problems you are facing is have already been discussed in these forums or you can send the photos of your set-up and explain your problems, and the community will help you solve your problem.
The diygokarts forum is the most active and helpful forum out there (You might have already come across that forum), I suggest you make the most use of that forum if you are new to go-karts.