A very common problem with the Fizzy can be stripped threads in the crankcase which hold the cylinder studs (see picture at left).

We already have the helicoil repair kit, but decided to make up a simple jig so we could end up with a job really well done. The jig is a block of steel -- about 1-1.5 inches deep, long enough to fit over the crankcase mouth, and a width of approximately 1-1.5 inches. It has ¼” hole, accurately drilled, so it’s all squared to the bottom face of the jig. (And it just so happens that our helicoil set recommends the damaged hole to be drilled out to ¼”!)

Drilling the jig was no problem, as we have a pillar drill. However, our hand drill was not around; so, undaunted, I ground a square on the end of the ¼” drill bit and was able to use our tap wrench for the driving medium (see photo at left for Rex in action with the drill jig).

Here, now that the drilling is complete, you can see the tap being used to form the oversized thread (which will accept the helicoil). To keep the tap square, a hole was drilled to keep the threaded portion of the tap supported, while the upper portion of the jig was drilled larger to suit the diameter of the shank (upper section of the tap).

This made it so easy! In the past, having attempted to do this “by eye,” and sometimes failing, I realised this simple correction would bring a much better end result.

And here it is -- the completed helicoil repair, as good as new!