battery size (is too small harmful to system?)

Hello.
Dismayed to see that the battery in my kz550a2 is 2 sizes smaller than recommended. My bike apparently needs 12ah and the one in it is 9ah (amp hours).
I just got new sprockets, chain and tires so it would be nice to wait a few weeks before buying new battery---AS LONG AS THERES NO HARM DONE.
PO rode with this battery who knows How long.
Wisdom shared is wisdom deeply appreciated.

I'd shop around and get the largest in amp hours that will fit the battery box.

My undestanding is when Kawasaki designed these bikes it was for a certain size battery. A smaller battery might get overcharged as the regulator/rectifier is sized for a specific battery(I might be wrong).

If the rest of the electrical system is OK, you should be safe to run. The system will still charge to about 14V which is right for the battery, but the battery just has less capacity and a higher internal resistance which equals less cranking Amps. However, the smaller battery will wear out faster (depending on how much you have to crank the starter) and your headlights will get a little dimmer at night sitting at a red light with the engine idling. Should be safe but if you hear the starter slowing down during cold crank, chuck the battery it's hosed.

A good test is to pop all the plug wires, put a voltmeter on the battery, and crank the starter over. If the battery voltage drops below about 9 - 9.5V, you need to pitch it.

bountyhunter wrote:

...A good test is to pop all the plug wires, put a voltmeter on the battery, and crank the starter over. If the battery voltage drops below about 9 - 9.5V, you need to pitch it.

Wondering how similar this is to an "official" load test at the local AutoZone.

Good Fortune!

MFolks wrote:

I'd shop around and get the largest in amp hours that will fit the battery box.

My undestanding is when Kawasaki designed these bikes it was for a certain size battery. A smaller battery might get overcharged as the regulator/rectifier is sized for a specific battery(I might be wrong).

+1 I agree!!

Patton wrote:

bountyhunter wrote:

...A good test is to pop all the plug wires, put a voltmeter on the battery, and crank the starter over. If the battery voltage drops below about 9 - 9.5V, you need to pitch it.

Wondering how similar this is to an "official" load test at the local AutoZone.

Good Fortune!

The cold starter crank is the worst case load the battery will ever see. If it can hold up enough voltage to give good ignition while it turns the starter, it's usable. The automated loads do a lot more testing but some kind of "full crank" test has to be included to measure CCA (cold cranking Amps).