Why is my clutch smoking on my Go Kart?

I’ve written several comments on this topic in the past, but I think it deserves a repeat, because there are two possible reasons why your clutch is smoking. I usually look at one of the most likely reasons, but in this article let’s talk about the two possible causes of your go kart clutch smoking.

The fundamental understanding of karting is needed first.. The driveline generally consists of a clutch controller and the driven shaft sprocket. The drive shaft sprocket is mounted directly to the rear drive shaft which turns the drive wheels. This is a one-step system, or a one-ratio system.

The centrifugal clutch used on most karts uses weights that are mounted internally to the clutch that are thrown and press against the clutch bell. The bell housing, in turn, moves the teeth of the sprocket drive sprocket.

Typical clutch has 10 to 12 sprocket teeth. As a general rule of thumb, any clutch that has more than 10 to 12 sprocket teeth will cause driveline problems. Problems such as smoking clutch.

The engagement of the weights to the clutch bell occurs at a certain rpm. Usually these rpm are around 1800 to 2000 rpm. The engine needs to exceed this rpm level and cause the clutch pack to stick and eventually engage the walls of the clutch bell. The smoky look occurs when the clutch engages but does not fully engage. If extended engagement occurs for too long, the clutch will start to smoke and eventually damage it until the weights just slip and maybe even crack and break.

As I said at the beginning of the article.Long-term engagement occurs due to two possible reasons:

1.) The engine is not powerful enough to get past the commit stage

2.) Clutch weight rpm not high enough.

The engine is not powerful it is usually the result of a mismatch in the proportions of the rear drive wheels. So the real reason is that the ratio is not steep enough and thus the engine smokes the clutch.

(Another possible problem can occur is that if the clutch is made to engage at lower rpm than the engine can achieve, the engine may not have enough power, and the engine will suddenly (more like violently) shudder and it will stop. It is not uncommon for the motor to have so much power that it spins backwards momentarily).

The second way the clutch will smoke. is if the clutch rpm never reaches engagement speed, or is close to engagement speed, but not high enough above engagement speed to get a lockup. This will smoke the clutch and is prevalent on mismatched output shaft systems.

The remedy for the first smoking clutch. The problem is altering the driveline so that the overall ratio is steeper. The simple method is to increase the diameter of the rear sprocket. Programs have been written that will estimate whether or not your clutch will smoke, usually found on websites or available for purchase through various websites. Usually what happens is that the hp ratio simply won’t be possible using the simple one-ratio system. Therefore, a jack shaft must be added to make the relationship even more pronounced. In other words, making it a two-proportion system.

This is where guys who install intermediate shafts need to look out for. Typically, the clutch cannot be placed on the input shaft drive, with a ratio ahead. This will cause the clutch to rotate too slowly, even though the overall ratio is correct. Therefore, the clutch engagement rpm must be taken into account; otherwise the clutch will smoke at the countershaft mounting position.

The bottom line is if the clutch does not activate due to too little power or too slow a clutch speed, then the system must be changed by altering the ratios behind the clutch or ahead of the clutch.