Flat spot on my otk chassis


After taken my motor of the chassis, for a service… I noticed a flat spot behind one of the motor engine brackets :frowning:

Any tips and tricks, on how I could straighten this area out again ??

Looks like the engine was overclamped a few times and it deformed the chassis tubing. Not a lot you can do really, at least not a lot that’s practical.

I have seen guys in auto racing use steel ball bearings driven through their Headers after they have taken a hit and deformed the tubing. The idea is simple enough. Find an old ball bearing slightly smaller than the inner diameter of the tubing your are trying to open up. If it’s a straight shot, insert the bearing into the open end of tubing and use a long enough steel rod to drive the ball through the deformed section with a hammer. On Headers, the ball will simply fall out the other side of the tubing. On a kart frame, the other side is blocked. You may have to leave the ball in there, but it shouldn’t hurt anything.

I have seen inserts for axles to prevent them from distorting when tightening the grub screws. Has anyone heard or seen anything similar for frame tubes where the engine mount clamps? Sounds like it would be a low cost insurance to prevent something like this.

Axle Stiffener listed as item “G” in the OTK Axle Chart:


First thing I would check; is that section of the frame rail still straight on top. Just use a straight edge on the top of the frame and see if there’s any air under the straight edge.
Fixing it is a little harder. One way, cut that section out, or the whole tube from the Nerf bar socket back. Make a sleeve that will fit inside the tube before will welding it back on. Lots of work.
If it’s not bent, I wouldn’t worry about it too much. Maybe cut another piece of bigger ID tubing, cut to fit, that will cover it and weld it on. Don’t go crazy on the welding, do it in small stages to keep the heat down.
A ball bearing that will fit the ID of the tube and welded onto a length of steel bar could be driven in to swage it out. That would be a little tricky, especially getting the swage bar out again.

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What about instead welding the ball bearing to a threaded stud/bolt. You could then use a slide hammer to pull the ball back out.


Thanks guys…

The ball bearing thing, is a very very good idea… I think i’m going to try this.

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