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1990 ninja 750 dead battery/ bad alternator

3K views 5 replies 3 participants last post by  fitbmxseries1  
#1 ·
trying to help a friend out here but he took his bike out for a ride a few days ago and it died on him so he replaced the battery after getting it tested but again it died today. the previous owner said he replaced the alternator and belt? i didnt think it had a belt but i havent looked at the bike yet or delt with an older one. Im heading over there tommorow to check i out. how should i check if the alternator is bad or if its just bad wiring. any ideas from my vague description? lol
 
#2 ·
The ZX750 H2 1990 does indeed have a belt.

Unlike most conventional bike charging systems this bike has the Gen & Reg/Rect all in one unit

So diagnosis is often made easier.

Make sure the Battery is fully charged.

Start the bike up and run it around 3.5 to 4k revs with the lights on and you should get around 13.5 to 14.8v charging voltage at the Battery.

If not then you need to check the associated wiring from the Battery to the Alternator.

Then see if the Belt has come off (There's a small black plastic cover over the belt which can be removed for inspection)
It's not uncommon for the belt after replacement to become slack enough not to drive the Alternator if it was over tightened when fitted. (There's a special Kawasaki tool used for belt tension)

Inspect the Alternator to see if they fitted a used one, Quite lickely as there loads of $ new and it could also be knackered.

I've ruled the Battery out as it's had a new one fitted.

Pic shows the setup and the belt.

Image
 
#3 ·
im going to head over there at like 3ish today to test the alternator. weird thing is that he was able to just start it right up yesterday after about an hour after it died. then he would ride it and it would die, and the starter would just click as if the battery was dead. then hour later it would start up like nothing happend
 
#4 ·
Not an unusual occurance especially with a new Battery.

The Battery gets discharged with use and will recover if it's left for a period without use.

This will only go on for a short time before the battery is unable to perform this trick and starts to remain discharged until you actually charge it again.
 
#5 ·
If the battery gets sulfated(an internal discharge condition) it may never regain the ability to retain an electrical charge and must be replaced.

Check the output voltage of the alternator with the engine running to see if it's working at all.If the belt looks good, you may have worn parts or electrical problems requiring rebuilding/replacing the alternator.
 
#6 ·
well had the alternator tested and put a new belt on and its still doing it. while its running i only get 11v when its running at 4k checked wiring from alternator to the battery. anything else cause this?