This is a gear that transfers force from a motorcycle kickstarter to the transmission. What method should I use to repair the missing teeth.

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  • 1
    $\begingroup$ Why isn't outright replacement an option? If some of the teeth were worn enough to fracture, then the other teeth have undergone similar stress and will likely fracture in the near future. $\endgroup$
    – user16
    Nov 14, 2018 at 0:15
  • $\begingroup$ It is possible you can build up material to take the place of the broken teeth but the chances are slim to none that you are going to match the profile of the existing teeth. Gears are not just toothed wheels, they have a rather complicated geometry. If you don't get the profile quite right, they won't mesh correctly and won't transfer power smoothly. It would be great fun to try to machine something that would work correctly but if you want to use the cycle rather than fiddle around in the machine shop, your best bet is the junk yard ($) or the dealer ($$$). $\endgroup$ Nov 14, 2018 at 0:22
  • $\begingroup$ @user1683793 Not to mention that the original part was forged with specific stress lines under consideration, and there's no way to glue/weld new teeth on and maintain that strength. $\endgroup$ Nov 14, 2018 at 19:19
  • $\begingroup$ It is very possible that the gear is powdered metal ( steel) indicated by what I can see of the fracture. And regardless, it is unweldable for any less than the cost of 10+ new gears. $\endgroup$ Nov 14, 2018 at 21:19

2 Answers 2


Oddly enough, this problem can be fixed using a set of car keys and your wallet. Here are the steps to follow:

1) put the keys in the ignition of your car, start it, and drive to the motorcycle scrapyard.

2) once there, exchange several pieces of local currency for a gear pulled out of another identical motorcycle.

3) place the gear in your pocket and drive your car home (optional step: purchase a six of your favorite dry-hopped IPA before arrival).

4) installation procedure is the reverse of the disassembly procedure.

5) after washing hands, open the first bottle of IPA.

6) share and enjoy.

  • $\begingroup$ I went with this solution, The gear is in the mail now. $\endgroup$ Nov 15, 2018 at 15:01

First you need to get rid of the leftover cups and cones by grinding it to have a smooth surface.

To get the best result you have to choose the same material but if you don't know the exact composition then, you can choose a similar materials but make sure the extra material has a good solderability, and it has to be compatible with the base alloy.

Then warm up the area, and try to distribute the smelted alloy all over the area.

The last step, is to machine the teeth.

It won't last as long as the new one, in fact warming up the gear weaken the alloy, it means the old teeth near the missing area, are likely to fail.

  • $\begingroup$ Would welding wire work well as the smelted alloy? $\endgroup$ Nov 13, 2018 at 23:07
  • $\begingroup$ @TylerB.Joudrey then you have to know the base alloy, not every type of welding wire is compatible with the base alloy, i think the base alloy is mild steel. $\endgroup$
    – user14407
    Nov 13, 2018 at 23:12
  • 2
    $\begingroup$ And final heat treatment... $\endgroup$
    – Solar Mike
    Nov 14, 2018 at 6:23

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