I have had some trouble in the past with my Rotax exhaust. When I started karting, I was unaware of the importance of exhaust maintenance. I noticed my kart’s engine sounded a lot ‘unhealthier’ than the rest of my competition. I experienced more misfires and a decrease in my engine’s performance.
So how do you maintain your kart’s exhaust? You need to replace your exhaust matting, clear off any rust on the outside of the pipe, and repaint your exhaust with high temperature paint. This might sound difficult; however, this article will give step-by-step details for perfect exhaust maintenance.
In this article I will detail 6 tips for exhaust maintenance. These will range from quick solutions to more thorough maintenance procedures. This article will ensure that your engine is running at optimum performance, and you can find those extra tenths of a second you need for pole position.
Why Is Exhaust Maintenance Important?
The exhaust is a key part of the 2-stroke engine unit. A Rotax exhaust is a very reliable system, however it does wear out with use, as any part on a kart does. High wear on your exhaust can cause you major engine problems in the long run, especially if you are racing.
My kart was always struggling on the straights, and I could never understand why… Until I started to properly maintain my exhaust. An exhaust must be regularly maintained to keep your engine running at its peak performance.
Tip 1 – Exhaust Installation
We will start off with the installation of your exhaust. This may be useful if you are buying a kart new and need to assemble it, or if you are replacing your exhaust, sending it into a workshop for repairs or just need to check for any damage.
- The first step is to attach your two rubber bumpers to the retaining plates. These bumpers act as shock absorbers while you are throwing your kart around a circuit as fast as possible, going over bumps on the track surface or running too wide over the rumble strips. Without these, your exhaust will vibrate too much and cause damage to the exhaust manifold on the engine; expensive damage.
- The next step is to attach these two rubber bumpers to the underside of the exhaust first using a 13mm spanner. Then you will fix the springs onto the exhaust and retaining plates. Use a spring puller or pliers to do this. Be careful not to stretch the springs, as this will render them practically useless.
- Now that the main exhaust is assembled, install the exhaust gasket onto the engine outlet. The next step is mounting the exhaust to the chassis. However, before doing that, first ensure that the exhaust fits onto the engine outlet gasket perfectly, and the rubber bumpers are resting on the chassis exhaust mounts.
- Fix the screws into the chassis mounts; not too tightly, however.
- The final step is to secure your exhaust system to the engine using two springs. The springs will attach the top of the exhaust to the actual engine, just behind the engine outlet.
Tip 2 – Look For Cracks In Your Exhaust System
Regularly checking the outside of the entire exhaust pipe is crucial. You should make this a habit when cleaning your kart, as this will be the easiest time to spot any cracks which may be hidden by dirt or grease. It will save you a lot of time and a lot of money.
Replacing an exhaust system is not cheap. Check the pipe for cracks that might start to show over time. This should not be happening however, if your kart’s exhaust is correctly mounted.
Some common places for cracks appear:
- The exhaust chambers and silencer
- Chassis mounting brackets
- Welded areas
- Engine outlet connection
Do keep in mind that as per Rotax regulations,you are permitted to repair cracks on your exhaust through welding, however, modifying the exhaust system is illegal.
Tip 3 – Exhaust Matting
This will likely (and hopefully) be the majority of your exhaust maintenance. The matting inside the exhaust silencer has a recommended service life of 6 to 10 hours. This can easily be overlooked because of its short lifespan, and because you can’t actually see the matting from the outside of the exhaust pipe.
When the matting starts to burn away your kart will lose engine performance, and it will start to sound louder and ‘unhealthier’ than the other karts around you. When it burns away too much you will start to see hotspots on the exhaust. These can easily be seen if your exhaust is clean and painted because of the hotspots burning through the exhaust paint.
Here is a detailed step-by-step guide of exhaust matting replacement:
- Drill the rivets off the end of the exhaust muffler, starting with the top one. We will be replacing these with a different solution in a later step. You might have some trouble removing the rivets, with the drill. Try to angle your drill slightly differently or use a set of locking pliers to hold them in place.
- In order to access the other two rivets, use the pliers or a spring puller to remove the exhaust springs that hold the muffler in place where it attaches to the main exhaust chamber. This will allow you to rotate the muffler and gain easy access to the other rivets that need to be removed.
- Once the rivets are all removed, put the springs back in order to hold the muffler in place. This will make your job much quicker and easier than removing the whole system.
- The next step is to remove the stinger (the perforated tube inside the exhaust).
- You will see the old, burnt wool matting inside the exhaust. Use your pliers to remove it carefully. Grab the matting with the pliers and rotate it (like how you would wring water out of a towel) and try to pull as much of the matting out as you can. The more careful and methodical you are in this step, the more work you will save yourself in the next step.
- Now you need to ensure that all of the old matting residue has been removed inside the exhaust. There are two methods in which you can do this. The first is to use a torch and a long steel rod and pull out all the excess and burnt off matting. Depending on the state of your matting, this could take some time. The other method is to start the kart up, so that all of the excess matting is blown out of the exhaust. Warning: this will be extremely loud, so always ensure that you and everyone around you are wearing adequate ear protection!
- Roll up the new matting around the stinger as tight as you can. You may have to roll it multiple times to get a good fit on the stinger. Warning: it is recommended to wear gloves when working with the exhaust matting as it can cause skin irritation due to the fibreglass. Always ensure you have gloves ready, especially if you are prone to skin irritations.
- Put the stinger, with the new matting rolled around it back into the exhaust. This can be quite a tight fit and you may struggle. Try to rotate it while pushing it into the exhaust. You can use a soft hammer towards the end to tap the stinger into place.
- As mentioned in step one, we will be replacing the rivets with a different solution. Use M4 x 10mm or M5 bolts in place of the rivets. These will be easier to undo the next time you need to replace your exhaust matting.
Tip 4 – Exhaust Mounts
Exhaust mounts are often overlooked during exhaust care. As mentioned in the earlier section, Tip 2, cracks can form on these exhaust mounts, which can lead to more extreme problems over time. These mounts are out of sight, and therefore they are checked less often than they should be.
My kart did not have the rubber bumpers that absorb the vibration from the chassis. This became an issue for me in Round Five of our national karting championship. My exhaust loosened off the chassis mounting during one of the heats. This could not be fixed during round, and I had to race on with a loose exhaust.
This is heavily detrimental to your kart’s handling ability, and even further damages the exhaust unit itself. Therefore, the rubber bumpers that cushion your exhaust are crucial and will add to the reliability of the entire unit. They are not expensive, but can save you a lot of trouble, and a lot of money.
Tip 5 – Sealing The Manifold
Having your manifold sealed tightly is key to engine performance. Sometimes the exhaust does not fit perfectly on the gasket due to rust or the exhaust itself being slightly bent or damaged. If the seal is broken, you can suffer a loss of exhaust pressure and therefore engine performance.
In this case, you can get away with using a high temperature silicone sealant. Apply the sealant to the outside of the exhaust where it connects to the outlet. Be careful not to apply too much of the sealant though, as it can leak over into the exhaust and restrict the outlet.
Tip 6 – Paint
Always have your exhaust painted often. The only colour permitted by regulations is black, so unfortunately you can’t make it match your livery and helmet design. Using high temperature exhaust paint, paint as often as replacing your matting.
This will help you to identity the hotspots mentioned earlier when your exhaust matting starts to burn away. You will easily be able to recognize when it is time to replace it.
Exhaust maintenance is such a vital part of overall kart care, though it is so often overlooked. Some people are intimidated by having to work on the exhaust because they do not understand it.
And some others are simply unaware of the fact that the exhaust requires maintenance. I hope that this article has helped you to understand your exhaust better and guided you to perfect exhaust maintenance.