Main Jet Thread Repair

Wed Sep 14, 2011 8:07 pm

This is the heli coil I used to repair the stripped main jet hole in my carb. Its 1/4-28 thread. This repair is easier if you buy a complete kit. I picked up one on ebay for $22.00. The coils that came in the kit were just the right length for this repair. They are the same length as the threads on the jet.

Here, I measure the coil to see what size the outer hole must be to allow the coil to pass through.

Drilling the outer hole. I used a 3/8 bit. Be careful not to drill beyond the fuel bowl!!

Here, I am tapping the hole to accept the coil. I didnt have to drill the carb body out because it is soft metal, and it was CLEANLY stripped of threads. You will also note the finish nail in the top of the carb. I used it as a depth gauge reference for the tap.The tap, while it says 1/4-28 is not a standard tap, but a STI (Standard Thread Insert) Tap. It is made specifically for the coil size OD.

And here I an installing the coil with the installation tool that came in the kit. Once I got it through the outer hole, I dripped 1 drop of red loctite on the coil and screwed it in place. The tricky part is removing the tang after install. I used an old drill bit just smaller than the id of the coil, dropped in the hole backward,and popped it off with a small hammer. I tapped it on the workbench and it fell out (finally). Once done, let the loctite set overnight, and just reassemble the carb and your set!
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