This 400F is undergoing some subtle changes. In keeping with the owners wishes, no modifications to the stock chassis can occur, and all modifications need to be able to be returned to standard.
One of the strategies is to reduce weight. For small capacity engines this is often the single most effective performance enhancement option, at least from a cost effectiveness perspective.
The stock indicators on a 75-77 400F are on the large side of the ledger. They can be replaced reasonably simply, and cost effectively, and most modern options have some level of flex in the design - unlike the original (i.e. you can hit something without bending the OEM equipment).
Here is the OEM cast blinker compared to the aftermarket...weight reduction > 75%.
As we cannot modify the chassis \ frame in any way we have chosen to use a friction (interference) fit, secured with an additional fixing.
Starting with standard 1\4 inch fuel line, a shop knife and a file, fashion a rubber plug to create a snug fit. Note the factory orifice \ ground cut, to accommodate the pinch bolt, on the stock blinker casting. We will use that later to good effect.
Fuel line cut to length.
Rough check fit. This will expand when the 1\4 inch bolt \ thread is wound in.
Slide on a small pipe clamp...
The rubber plug wound onto the blinker thread, ready to be offered up to the stock indicator arm.
Slide the wires into the indicator arm and push through the hole at rear for joining with the stock harness.
And now press home the aftermarket indicator assembly. This should be a snug to tight fit.
Drill out a small guide hole for the retaining nut. Note this hole is through the pipe clamp band and a few mm into the rubber plug, it isn't modifying anything Mr Honda built.
Here is a close up. We used a small mushroom head bolt, approx M4 size, which was ideal.
And from another angle, note how short the threaded shaft is.
The finished solution.
And a close up as installed.
Ready to hit the road. The OEM components are stored safely and can be re-installed in a few minutes.