Kart Engine Mount Troubleshooting... When the motor or clamps keep working loose

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Inspired by a facebook group discussion that will disappear like all the rest…
Please add your insights and experiences below…

If you have an engine mount that refuses to stay put, or a chain that keeps falling slack here are some items to check.

  • Ensure the mount and it’s clamps match the spacing and size of your chassis.
    Remember many karts are comprised of different rail sizes from side to side or front to rear, so it’s important to check you have the correct size. The CRG family has a slightly different center-to-center spacing on the motor mount to others, that’s a common one that catches people out.

Here’s a great video from @Norcal_Karters that shows you how to accurately measure the frame size and spacing:

  • Inspect the area where the mount meets the frame rails
    Are the rails clean where the mount contacts them? Dirty rails, no good!
    Pay close attention to where the mount might also catch on a weld for a sidepod or seat bracket mount.
    Flattening of the frame rails is another thing to inspect for.

  • Clamp Bolts and thread condition.
    Clamp bolts and threads should be clean and generally in good shape. However they should NOT be lubricated. Inspect for any thread damage or warping, replace if unsure. Replacing these is good preventative maintenance.
    Often the threads in the mounts are aluminum which is not always ideal. Some racers have drilled these out just deep enough to put a nut in place to use those threads instead.

  • Use a motor stop bolt behind the motor.
    Essentially essential. You want to have a motor stop bolt wherever possible. It’ll make you and your chain happy.

  • Clamp Condition
    Clamps should be free from dirt and not curved/bowed from overclamping.

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Any thoughts on tightening torque guidelines? They will vary given the different bolts at play, but it would be nice to have them.

I’ve always done it by hand myself, but if I could do it reliably and consistently with torque wrench.

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If there is a torque value, I’d love to have it. Have heard about the wrong way to tighten them up. A 20V hammer driver used on a Tony kart. Flatten the rails right up.

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I had a situation last fall where the kart felt ok but whenever I would come out of a turn and go to gas, the chain would fall off. After a bit of noodling around, it turns out the weld underneath the engine had cracked. Funny thing is, you couldn’t see it with the naked eye.

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A couple thing she I’ve noticed just over time.

The weld ridge area Berry mentions in this video really is a thing. If you tighten the clamps down on that it can cause issues on some tracks, at least with Briggs mounts which are already struggling due to the torque of the Briggs.

The other factor that is surprisingly common with something 2 cycle mounts is the clamp bolts being slightly too long. So long, in fact that they will press against other part of the mount when tightened on some chassis. I’ve seen this on a couple chassis with the Odenthal 2 cycle mount for engines like the Rok or X30. It’s remarkable how much that causes problems.

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I also like to put some emery cloth on top of the rails, gritty side up, so the mount can’t slide as easily, and so the powdercoat doesn’t get all chewed up by the mount.