Updated and revised: 06.13.15
Thank you to the folks on one of the Kawasaki Concours forums for this idea. They had a forum mishap and I can’t find the original post.
Suddenly the bike needs a new battery. There are lots of options out there, but it happens at a time when I want to use the bike, which means this is about taking advantage of local retail economics. A new 18ah MC battery at the auto parts chains is typically $100 for an 18ah SLA (Sealed Lead-Acid). I’ll need to charge it before use, conveniently these stores sell chargers as well, in my case they suggested the wrong one, which shortened the battery’s life. Out the door with the wrong charger, around $140.
The next time, thanks to the Concours guys, I went to Harbor Freight and bought an automotive jumpstarter for under $40. It came with a Sealake 17ah battery, which lasted nearly 3 years of wide temperature variations, long periods of storage, a formerly feeble charging system, and rare Battery Tending. I liked it well enough that there are now 3 jumpstarter carcasses out in my shop. The batteries easily spin the stout Bosch starters that were stock on Loopframe Guzzis.
Included with the jumpstarter is an internally-mounted and detachable wall-wart charger purpose-built for that battery, AC cord, volt meter, 12v light, switches, heavy wire leads, including 2 short jumper cables, a heavy-duty 12v switch…if you like to scavenge and make things from parts these can be a great value. For another $10 or so these can include a tiny air compressor that can be removed and wired to work with SAE battery tender leads or other 12v accessory plugs.
June 2015 Update: I purchased a HF jumpstarter in the new red case, it came with a 17ah Sealake installed. The 18ah battery that came in the Costco jumpstarter is still taking a charge after being purchased in 2010.
In the interest of economic science, I took apart a jumpstarter I bought from Costco, which runs about $70. It comes with a battery about the same size, but rated 18ah. I actually use that one for work projects, so it got put back together. The second photo shows the small compressor which could be removed and used as a portable tire pump.
I adapted a similar 12v pump by removing the space-hogging plastic case and adding an SAE connector so it runs off my battery charging pigtail. That pump, at $4.99, might only last once or twice.
Other Moto Guzzi loopframe battery options available in this informative compendium…http://www.thisoldtractor.com/moto_guzzi_loopframe_batteries.html