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How to Mount Your Seat
New or beginning karters are faced with many new challenges. If it is chosen to own and maintain personal equipment there is even more to be learned. Karting in its nature is unique to many other motorized sports. The general lack of manufacturing standards places emphasis on the karters ability to adapt to the equipment. Never the less, we must all cope with the challenges of mounting the set.
The seat of the kart is critical when considering the driver kart interface. Your karts seat controls your mass and more importantly your karts handling characteristics. Similarly, the driver must fit in the seat so that both the driver and the seat can do their jobs effectively.
Mounting a seat is no small task; of course before mounting begins one must first find the proper seat. Over the years I have found that the Tillett T-8 fits me best, but everybody is different. I recommend actually sitting in a few seats before purchasing. A good seat will fit you snugly around your upper body, but not so tight that it actually squeezes. Your hip area should not feel the side of the seat, however, the seat should not fit you loosely. If your body can slide in the seat it is too big, if you are squeezing into the seat, you are generating preloads and probably pressure points on your body before you even hit the track. Take your time and get the right seat! The difference may make your weekend fun or make your weekend a nightmare.
When seat shopping you may find that there is a very large variety. Not only are seats made by several manufacturers but they come in a variety of prices, shapes, rigidities, colors, carpeting and so on. Personally, I find that the plain old fiberglass seat works best for me. It is easy to clean, easy to mount, and with some tape can be easily padded to fit my body characteristics. Ultimately, seats are very personal and you will need to weigh the pros and cons off all options.
One of the first lessons I learnt is that rushing the seat process will come back to bite you in the end. Improper or poor seat alignment can truly ruin your karts handeling characteristics. Also, a rush job may drastically shorten the life of your seat. Finally, the seats plays such an instrumental role in kart peformance getting as good a job of mounting is critical. A poorly mounted seat can cause weeks of frustration and consequently get you behind the learning curve.
The materials you will need include: flat surface(floor), eight 219 Sprockets, 1 seat, 1 drill, One 8mm drill bit, a tape measure, some ballast. As I mentioned before, there is a large variety of seats. The two main variables that will affect you during this process is the seat bottom. Some seats are flat bottom and some are not. The flat bottom seat is touted to have advantages with center of gravity, however, its real advantage is in mounting. This is because it tends to simply sit flat on the ground. In contrast, their round bottom counterpart may wobble and move while mounting and can be rather frustrating. Either way, let's get started with the job at hand.
The method I am showing you is advantageous because it is done without special tools and is equally effective at the track and at home. To start, remove all four wheels. If the axle sprocket is larger than 85 teeth or the motor mount clamps are excessively thick removing these may also be required. Set the chassis on a flat surface like your garage floor. Many manufacturers ask that the seat be placed slightly below the frame. To do this we will simply raise the frame with shims and allow the seat to hang below the frame and rest directly on the floor. Consult your manufacturer for these measurements. Now you will need something to shim the chassis with. A common set hang setting is about 5-10mm. Yet, with smaller people(usually kids) this may be different. I have found that a stack of two sprockets is a great shim. Use the shims under the rear of chassis beneath the cassettes, and also beneath the waist tubes. Your chassis should at this point be resting on shims and around 10mm off the floor.
Place your seat in the frame and position some ballast in the bottom of the seat. This ballast will help keep your seat positioned. If you are using a round bottom seat some provisions may need to be made. I usually just block the back the seat to keep it from rocking but try to keep it simple. Position the seat using your tape measure and the factory provided measurements. It may also be useful to eyeball the seats position. Look at the seats position relative to the steering uprights, and also its position side to side in the kart. Generally, an adult seat will be pushed against the engine side seat strut and then the opposite side strut will be bent the appropriate direction. This however may be different in some extreme cases.
The struts themselves are rather stiff a large lever like an old axle is the right tool for the job. A second person can be useful in preventing the chassis movement while bending the strut. Bend the strut in small incriments checking the seat fit regularly. Try to avoid bending the seat strut back the other way as this may comprimise the seat struts integrity.
Before drilling any holes you should first align the left and right seat strut tabs. You do this for a few reasons. First, if the tab is incorrectly aligned it may hide the fact that your seat strut needs to be adjusted further. Second, a tab that hits the side of the seat irregularly may cause unusual wear characteristics which ultimately may shorten the life of your seat. Lastly, a tab that is not parallel to the seat may pre-load or contort the seat. The seat should not be preloaded in the frame!
After you have adjusted the seat into the perfect position and moved all struts and tabs accordingly it is time to start drilling. Do one side at a time. Preferably, the engine is not on the chassis and you simply drill through the strut and then through the seat. Again, it is helpful to have another set of hands. In this case the second person should hold the seat stable and counteract and drilling forces. Also, drill slowly as to prevent large amounts of fiberglass dust and to avoid moving the seat. Note: Fiberglass dust should not be inhaled! Use proper personal protective equipment! Once the first seat strut hole is drilled place a bolt through and snug it down. Measure the seat placement checking for movement. If it is in place go ahead and drill the other side. Drill that side using the same precautions as above.
Now that the top two struts are done we will need to work over the bottom tabs. For this, it is best to have the kart back on the stand. Yet, the same rules apply. Use a crescent wrench and tweak the tabs as to achieve the necessary parallel lines. On many chassis washers are needed to space the bottom of the seat. However, it is critical that you try to maintain the correct seat hang (the distance the seat hangs below the chassis). On a flat bottom seat just keep its bottom parallel to the chassis. On round bottom seats you will need to monitor the depth that the seat actually falls below the chassis.
To finish the job you will need to drill the bottom holes. To do this you will need to position the seat down onto the appropriate washers. This is done to assure the proper height. You can now either drill down through the seat and tab or do the reverse. Down through is typically much easier. Shining a light up through the tabs hole may make your drilling more precise. Again, take your time and drill slowly. Lastly, insert the necessary hardware and tighten all of the seat bolts down firmly.