From:Dave Hennessey
Subject:RE: Battery for 1929 KJ / Wiring diagram ? Date:Sat May 18 16:47:17 2013
Response to:4710
The number of choices in 6-volt batteries is pretty limited these days.

One alternative is to use one or two of the sealed Power-Sonic PS-640F1 batteries, as described at
Two of these, wired in parallel for more amp-hours, will fit nicely in the KJ battery box with some foam rubber padding.

These are typically used in EXIT signs in commercial buildings, and were not designed for the vibration and shock of motorcycles. Harley Hummers are typically driven slowly around the neighborhood, and these batteries work well in that application.

In KJs, where they encounter potholes at 60 mph, they seem to fail abruptly and completely. So using two in parallel, where you can quickly bypass a failed unit, would be the best bet. Purchasing three of them (at $10.xx each), which qualifies for Amazon's free shipping, will provide you with a spare on the shelf.

This is what I use on my KJ. Not the best, but it works. Anyone got a better alternative?

Wiring diagram attached below. sells a decent repro harness, but patience is sometimes required with this vendor. I used one on mine, but I had to hack it up to accommodate my funky external brake light - which looks like it came off a 1950's school bus - not altogether a bad thing in today's hectic 75 mph traffic.

Hope this helps.


Hello !

My shop is thrilled to be restoring a 1928 KJ ... can anyone recommend a battery that will fit properly into the box ?

Plus, does anyone have a wiring diagram ?

Thanks in advance !