TOPIC:

Hey all!

Just picked up my first kz, a 1977 400 I was reading the forums and stumbled upon a comment mentioning using a computer battery instead of a typical one, but the links provided by the commenter were broken. Does anyone have any info on it? I’m trying to decide between a capacitor, scooter battery, and a computer battery. Thanks all for reading!

Personally, I think one of these would beat all of those.

shoraipower.com

TexasKZ wrote: Personally, I think one of these would beat all of those.

shoraipower.com

Agree! It seems to me that rather than trying to use a computer battery, a capacitor, a scooter battery, etc. the best battery to use in a motorcycle is (wait for it) a MOTORCYCLE battery. Ed

650ed wrote:

TexasKZ wrote: Personally, I think one of these would beat all of those.

shoraipower.com

Agree! It seems to me that rather than trying to use a computer battery, a capacitor, a scooter battery, etc. the best battery to use in a motorcycle is (wait for it) a MOTORCYCLE battery. Ed

Now there you go making perfect sense again, Ed! LOL

I've had way more luck with a capacitor than any motorcycle battery. It has lasted over 10 years without a hiccup on my 550. I installed a spare next to it at the time and haven't needed it once. I got the capacitor free.

I've also had a worn out scooter battery last longer than brand new motorcycle batteries. On a Kz400 we used a scooter battery for close to 10 years. The scooter battery was already used when we got it. It was free as well.

I'm currently installing a computer UPS battery on a 76 Kz400. Actually, it's already installed but we still have to build the exhaust. These batteries can be had for about $15. We got ours free from a broken UPS unit. The thing with the computer battery is that you have to build a supportive battery box and make sure it holds snug with cushions and doesn not get stressed. The case is much thinner than a vehicle battery.

Obviously, these are only options as long as you don't want electric start.
The capacitor option is only for bikes with permanent-magnet flywheels, and a few wiring differences should be made when using a capacitor..

That link is for a lithium battery. I would trust these other options before a lithium battery... not that I'm totally against lithium batteries, but the google results for lithium fires don't look good.

loudhvx wrote: I've had way more luck with a capacitor than any motorcycle battery. It has lasted over 10 years without a hiccup on my 550. I installed a spare next to it at the time and haven't needed it once. I got the capacitor free.

I've also had a worn out scooter battery last longer than brand new motorcycle batteries. On a Kz400 we used a scooter battery for close to 10 years. The scooter battery was already used when we got it. It was free as well.

I'm currently installing a computer UPS battery on a 76 Kz400. Actually, it's already installed but we still have to build the exhaust. These batteries can be had for about $15. We got ours free from a broken UPS unit. The thing with the computer battery is that you have to build a supportive battery box and make sure it holds snug with cushions and doesn not get stressed. The case is much thinner than a vehicle battery.

Obviously, these are only options as long as you don't want electric start.
The capacitor option is only for bikes with permanent-magnet flywheels, and a few wiring differences should be made when using a capacitor..

That link is for a lithium battery. I would trust these other options before a lithium battery... not that I'm totally against lithium batteries, but the google results for lithium fires don't look good.

thanks for the well thought out message! I've actually read your stuff many times before when searching for the answer to the computer battery question, so when i posted this thread you were the person i was hoping to speak with! Can you elaborate on the differences in wiring you need to run a cap? Also, where did you get your info for the UPS batt? Are there any wiring differences needed in order to use the UPS batt? Also, what kind of UPS batt are you using? Thanks again!

Haha i've seen you around this forum while browsing the answer to my question, and you always seem so averse to people trying to do anything different for the sake of it! Can i ask why? Are you an ultra purist? I really dont mind either way, im just curious.

In order to run a capacitor, your charging system must use a permanent-magnet rotor. The 77 Kz400 D4 did not come with one, and I don't think the other 77 Kz400's did either. So you would have to find a way to convert your charging system to a later year charging system. That means replacing the stator, rotor (aka flywheel), and regulator and rectifier.

If you are removing the starter then you need a way to hold the starter chain inside the alternator housing. Or if you remove the starter clutch sprocket and chain, you will need a deletion arbor. The starter clutch sprocket covers an oil passage on the crankshaft end. The models which don't have a starter have a little piece of hardware to cover that passage. You could maybe just remove the chain and have the sprocket spin around with the crank... I don't know if that will put excess wear on the starter clutch, but I wouldn't chance it. They are getting hard to come by.

The slight alteration to the wiring is done after you convert it to a later year (which requires a bit of re-wiring itself). Some combo reg/rec units will have a brown wire on them. That brown wire should be re-routed directly to the white/red output wire of the regulator/rectifier. If the reg/rec does not have a brown wire, then you don't have to make any changes after your conversion.

Another alteration you will need to make is to have a switch to turn off the lights on the bike until after it is running. Or I prefer a relay that automatically turn the lights off when the bike turns off. Then I use the starter button to trigger the relay to turn the lights on after it's running. The lights act like a short when they are not turned on and will drain away the voltage from the capacitor when trying to start the bike. Once the bike is running, you give it a rev and turn the lights on. The momentum of the engine keeps it turning and the lights will come on and the engine will continue running.

The bike needs to be in good tune and start reliably in one or two kicks with a battery before attempting to go without a battery.

So instead of all that to run a capacitor, you can just run a small 12v battery. You don't really need to make any changes to run a scooter battery or computer UPS battery, other than to make a physical battery box. and new wire connectors. I pull these 12v 9AH batteries out of the recycling bin and if they have over 12v on them, I charge them and use them for various project. Some have lasted for years (after they have already been used for many years and deemed un-serviceable). So I'm getting them free. But you can get brand new ones for less than $20 if you shop around.

Here's one, but I never used that seller. You may want to find a local battery shop.
batteryguy.com/12v-9ah-sealed-lead-acid-...PEAQYAiABEgItUvD_BwE

I also use 12v 7AH batteries that have the same dimensions as the 9AH. The 7AH are older and cheaper but should work fine. Either should work fine as long as you don't leave the ignition and lights on with the engine not running.

The Kz400 frame is perfectly fitted for the battery. Notice how it sits perfectly between the frame tab and the support pipe. You have about 3/4" of clearance above the frame rails before you hit the seat pan. And the way I have the battery, the positive terminal would only come into contact with the document tray so it doesn't hit anything metal. When I get a chance I'll post a photo from the side with the seat and tank in place so you can see how the battery is mostly hidden.