Home > Chassis Tech >



Product Code: 004





Are You Listening?

By Mike Unger


I know times are tough all over, and finding a budget for a new chassis might be completely out of the question. So I suggest you simply look at what you have and consider a bit of restoration work. You might find out that the chassis you already have just needs some elbow grease and TLC to get it in top shape for the upcoming season. 


My son’s kart is a perfect example. It is a 2008 Kosmic T11 that I raced in Tag Masters and then he raced this past year in his first year in Yamaha Junior. The chassis works well, he still likes the way it handles and we ran quite successfully with it at the local series at New Castle Raceway Park. After a year of running local sprint races we finished the year with a 225 lap endurance race and needless to say it is in serious need of some work to get it in tip top shape.

Before you dive into a full refurbish you need to make sure the chassis is worth the effort. The first place to look is the undersideof the kart. Look for frame tubes that are ground flat due to contact with the track. If the tubes are only slightly damaged the integrity of the chassis is still acceptable and handling will be unaffected. But if the tubes are ground down to a point that there is only a few thousands of an inch of steel left before it goes through it is time to shop for a new chassis or at the least a new frame. Also while you are inspecting the frame look for cracked welds. It’s something you will do again after the frame is thoroughly cleaned but right now look for more obvious cracks. Most cracks will appear at the joints where two tubes come together or where brackets are attached. If you find a crack in the middle of a tube you should be more cautious. Repairing a tube mid length could alter the way the frame flexes and cause troubles on the track. Again look things over and decide for yourself how to proceed. If after the initial inspection you have decided this chassis is worth the effort it’s time for a complete tear down. You will need a notepad to list obvious things that need replaced as well as lots of rags, cleaning supplies, and patience.


For the tear down I suggest starting at the rear of the kart and working your way forward, starting first with the rear bumper. In my case the Kosmic has a full length plastic bumper that is attached to the frame tube though brackets. Remove the plastic bumper from the brackets, carefully inspecting the bolts and brackets for excessive wear, bent bolts and simply worn out components. If you find a bracket or bolt that needs replaced write it down on your notepad. Carefully organize your parts as you remove them. I suggest using a couple plastic bins to keep things organized.


After you get the rear bumper off its time to start into the axle assembly. This area tends to be the most critical and the most messy, rubber gloves may be in order. Remove the wheel hubs, sprocket carrier, keyways and inspect for cracks or stripped bolts. Make a note to replace as needed. After the hubs are removed spin the axle and carefully look for a wobble in the axle. The human eye has the ability to detect a difference down to a couple of thousands of an inch. If you see a wobble make a note that you will need to send the axle out to get straightened before reassembly. Just ask at your local kart shop for someone who straightens then. Often you can get it done for a fraction of the price of a new axle. Next remove the axle from the bearing cassettes. This will require loosening the set screws in the bearings, as well as the brake disk hub. After you have removed all the set screws and loosened the brake disk hub you can remove the axle. To do so you will need a large rubber mallet and some effort. Make sure to slide the axle out towards the engine side of the frame. After you get the axle to move far enough the brake disk keyway can be removed and the axle can be completely removed. If after initial hammer blows it doesn’t come free you should check again for set screws you missed or a sticking brake disk hub. Sometimes a screwdriver gently tapped in the slot in the brake disk frees things up. If that still doesn’t work you might need a friend to help hold things in place while you wind up and drive it out. Just remember that it was assembled by hand once before, it can be disassembled.


After you remove the axle, set it aside and remove the bearing cassettes from the frame. For most chassis this will also require removing the rear brake caliper assembly. While you are at it I suggest removing the entire brake system and setting it aside. We will inspect that system later. Once you have the bearing cassettes removed set them aside as well for further cleaning and inspection.


Next its time to remove the seat and all of the seat struts. When doing this, carefully check for cracks, elongated holes and worn bolts. Cracks and elongated holes can be repaired with a fiberglass repair kit. Bolts need to be replaced. Set the seat aside and move on to the fuel tank and floor pan.


Before you remove the fuel tank I suggest you cut the fuel lines away from the tank and discard them. Fuel lines tend to harden over time and need to be replaced periodically. I suggest discarding the fuel filter as well. With the lines removed unscrew the large wing nut to remove the fuel tank or if your tank is bolted to the floor pan remove as needed. Carefully inspect the tank for thin areas, weak seams and cracked fittings. Make a note to replace as needed. Fuel tanks tend to collect lots of dirt and grime over the race year but often can be cleaned up to look very good. If your tank in yellowed from having fuel left in it for too long it might be time to consider a replacement. 


The floor pan is next and the bolts that hold it in are likely ground down or full of dirt. These are very likely the bolts that will need to be replaced at least once a year. Getting them off can sometimes be a chore. Vise grips and patience is the only suggestion I can offer. After the floor plan is out you have easy access to the driver fairing and steering shaft. Remove the steering shaft lower bushing with a snap ring pliers as well. As with other parts set them aside for inspection and cleaning later


After the steering shaft all that is left is the front bumper and pedals. Carefully inspect the pedals for excessive wear and tear. The bumpers usually slide over tubes in the front and are fastened with bolts a simple tap with a rubber mallet and they will pop off for you. 


OK, now that the kart is completely dissembled it is time to clean and inspect each component before re-assembly. I suggesting cleaning and inspecting each component individually before putting them back on the frame. For this activity it is recommend some rubber gloves, a parts washer, a cleaning agent (WD40 is what I use), an old toothbrush, and lots of rags. Don’t use brake cleaner on any painted surface as it will damage the paint. I also suggest replacing old nylon lock nuts with new ones as they tend to loosen up after being on and off several times. New nuts and bolts are cheap insurance against a problem on raceday. 


The first thing to clean and likely the most time consuming is the frame itself. Use lots of cleaner and use the toothbrush to get into those hard to reach areas. Take your time and do a good job. After the frame is free of all dirt and grime wipe it down with a clean rag and place it on the kart stand. Now we will polish the frame up while inspecting each and every inch of the frame. Cleaning the paint is a step that will really make a difference in how good your frame looks in the end. I use Mequires paint cleaner for this step. You can find it at any auto store and you use it just like rubbing compound. It gently removes stubborn grime and restores the luster in the powder coat. Concentrate on one frame tube at a time and as you clean carefully look for cracks. If you find one you will need to get it repaired. To properly weld the frame you will need to get it TIG welded by a good welder. The best place to find such talent is in a race shop that builds full tubular frames. Before you take the frame, be sure to remove all paint from the cracked area. This will ensure that the weld will be clean and solid. In my case the right side seat strut broke right around the tab. A simple clean-up and a trip to my buddy who builds sand dragsters and it was fixed. After the frame is completely cleaned up and repaired as needed it is decision time. If the frame’s paint was able to be cleaned up enough for you liking you can proceed with the rest of the assembly. If not you should consider re-powder coating the frame. Do a search on the internet for powder coating in your area or ask around at your local kart shop for places that do it. You can usually get it done for around $300 in most any color you like. 


With the frame now complete it is time to start putting parts back on it. When I take parts off I don’t clean them until it’s time to put them back on. Using this technique I can focus on each and every component and make sure it’s right before moving on to the next part. I like to start with the rear axle assembly since it the most time consuming and messy.


The rear axle bearings and cassettes need the attention first. The bearings can be removed from the cassette by turning them 90 degrees to the cassette and lining up the slot on the cassette. After they are removed carefully wipe any grease and grime from around the bearing dust shield. Be careful not to push the grime into the bearings further as this will make your job bigger. After the bearings are cleaned spin them in your hands listening for grinding and well and feeling for excessive play. If what you hear sounds like someone grinding coffee or there is lots of play in the bearing I suggest replacing the bearings. Of course you can try removing the dust shields and cleaning it all out but since these bearings are very important to the performance of your kart replacing them with new ones is money well spent. 


Next clean up the cassettes and look carefully at the interface between the outer race of the bearing and the cassette. Often you will find deep scratches and grooves in this area. I suggest thoroughly cleaning and then using a scotch bright pad to smooth things out. After everything is cleaned up put the bearings back in the cassettes. Use light grease between the outer race of the bearing and the cassette to help the bearing adjust as the chassis flexes. Put the cassettes back on the frame using the original bolts as long as they are in good shape. Remember to use a thread locker of some kind to keep those bolts from backing out. Do not torque the bolts down until after we put the axle in.


Now it’s time to work on the brakes. Brakes being an important safety item and rebuilding them not necessarily a trivial matter, I suggest that unless you are very mechanically inclined you ask your local kart shop for help with the rebuild. Of course if you are comfortable a brake rebuild kit is available from your chassis manufacturer. Carefully disassemble the brakes, drain the brake fluid, replace seals and thoroughly clean. Use brake cleaner and be mindful to make sure all the components are surgically clean. During reassembly make sure to use thread locker as you did for the bearing cassettes. Also be sure to use the proper type of brake fluid in the system. Most brake fluids do not mix with each other. When in doubt consult your chassis manufacturer for help.


Before the axle goes in you will need to clean up the brake rotor. I suggest removing the disk from the hub and cleaning both with a very fine steel wool. Don’t rub too hard as you will remove the anodizing on the aluminum hub. Reassemble the rotor and hub using new steel locknuts. Never reuse them and never use nylon locknuts on the brake disk as they will melt from the heat.


The axle takes a lot of abuse in a kart and in order to make it easier to get in and out you will need to apply some elbow grease to it. I suggest using a small file to remove the burs caused by the set screws and medium grade sandpaper to smooth out the areas where the hubs attach. This will take a little time but will make the axle install much easier. After it is ready, slide the axle into the bearings through the brake rotor and into the far side bearing. Don’t forget that before you slide it all the way through you will need to put the brake rotor keyway in place. Now torque down the bearing cassettes bolts and check to make sure the axle spins freely. If it doesn’t, gently tap the cassettes with a rubber mallet. Often the bearings need a little bit of force to get everything aligned. After the axle is through, use a measuring tape to make sure the axle is centered in the frame. Now line up the set screw holes with existing bolt locations on the axle and tighten down the set screws. Don’t forget to use thread locker on the set screws. Now is a good time to safety wire the brake disk and caliper as well.


Next up is to move to the front of the kart. Put the front bumpers back on, along with the pedals. Carefully inspect the bolts that hold the pedals. They tend to wear over time and generate excessive play in the pedals. Replace the nylon lock nuts with new ones too. 


For the steering shaft make sure to remove and inspect the lower support bushing in the frame. For most karts you will need to remove a snap ring to get it out. Once out clean it thoroughly and check for excessive play. If needed replace. Too much play will cause for inconsistent toe measurements as well as a sloppy steering. When you put it back in place be sure to check to make sure the snap ring is seated properly. If it isn’t seated right it could be a safety issue. Replace the nylon lock nut and tighten. With the floor pan out of the way this is the time to safety wire or put the E clip on the end of the steering shaft.


With the steering shaft in place it is time to put the floor pan back on. The floor pan on Noah’s kart had a big sticker covering the whole thing. When new it looked very sharp but after years of use it is looking pretty rough. I removed the sticker and with some brake cleaner removed the adhesive that was still stuck to the aluminum. Then with some fine steel wool I cleaned it up and made it look almost like new. Attaching the floor pan will require new bolts and nuts. These bolts take lots of abuse so don’t cut corners here. In order to keep the floor pan from rattling I always use rubber washers between the frame tabs and the floor pan.


Now it’s time for the spindles and tie rods. Inspect and clean the spindles closely. Pay careful attention to the bearings in the spindles that support the kingpin. These small bearings take a huge amount of abuse and usually need replaced yearly. Also don’t forget the bearings in the wheel hubs if that is the style on your kart. Inspect the tie rod ends looking for excessive play as wheel as bent ends. It’s pretty easy to overlook a bent one in the rush to fix a bent tie rod at the track. Assemble the tie rods using new nylon locknuts. Alignment will come at the end.


Now let’s talk about the seat. The seat takes a lot of punishment not only from dragging over that high curb you like to hit but it also supports quite a bit of load on the racetrack. Check for cracks around mounting locations, elongated holes, cracks and damage to the bottom of the seat. If you don’t find anything then a simple scrubbing with some brake cleaner to remove the grim and your seat will be ready to go back in. 


If you did find some areas in need of repair I suggest a visit to your local automotive parts store to purchase a fiberglass repair kit and some rubber gloves. Make sure you clean the area to be repaired thoroughly and follow the directions on the box. I suggest 3 layers of fiberglass mesh for most repairs, more for big areas. To fix elongated holes simply put some tape over the hole from the inside of the seat before you apply fiberglass over outside of the seat. Make sure the fiberglass is completely dry before you re-install the seat in the frame. Like the rest of the kart, make sure you use new nylon lock nuts when you re-install the seat.


Now it’s time for the rear bumper. In my case it’s a full length plastic bumper that is fastened to the frame with long bolts that pull 2 wedge-like plastic pieces together that expands against the inside of the frame tube. Completely disassemble the wedges and clean them completely. Also swab out the inside of the frame tube to make sure there is no residue that would make the insert slip out on the track. Also check those long bolts, they take a lot of abuse and can bend. If they are replace as needed. Disassemble and clean all related pieces that attach the bumper to these long bolts. Inspect for wear and like the previous parts replace as needed. The rear bumper also needs to be cleaned. For this I used WD 40 and a small scrub brush. Scrub all the dirt and grime off using the WD40 then clean the WD40 off with brake clean. After all the parts are completely clean re-assemble. Use blue threadlocker on the nuts on the long bolts when you tighten things down. Don’t forget to replace the nylon nuts.


The final parts of the kart to clean up is the bodywork and nerf bars. If you have a sticker kit you will need to decide if it’s time to replace them or not. Decals take a beating, but they are really a great way to make an older kart look great. In my case and with the help of NKN and Decal Works I replaced the beat up original Kosmic stickers with a custom Decal Works kit. Installation is easy but does take some time and patience. Just follow the well written directions and your bodywork will look like new.


So there you have it, how to refurbish an older kart and not only make it look like new but also make it perform like new. In my case, minus the sticker kit, I spent about $20 in new nuts and bolts, $15 for a fiberglass repair kit, and $10 in cleaners and such. That is much easier on the wallet than a new $5000 chassis.t keep on coming.





Average Rating: Average Rating: 5 of 5 5 of 5 Total Reviews: 1 Write a review »

  0 of 0 people found the following review helpful:
5 of 5 Awesome! December 22, 2018
Reviewer: Blake sholders from Indiana  
Thank you for this! It helped a lot, you pointed out a lot of little things that I would have overlooked. You guys should make more tech blogs, i cant get enough of them!

Was this review helpful to you?