Diode location

I have a 82xj750j. The charging systems to be a little messed up. At an idle it charges 12.5 reved up it charges at 14.75. I looked at the yamaha site at parts and there seems to be a diode in the system. I just need to know where it is so I can check it on my multimeter. I am up for suggestions also. Maybe it doesn't have on and is built into the rectifier. In that case I will be getting a new one. Any advice would help. Thanks

 

Why do you think your charging system is messed up? Those voltages look fine at first glance.

 

Seems like too much voltage swing to me. I guess it is different on a car (tends to hold a more constant voltage) vs this. But this seems extreme. It is my first bike in years. I could be wrong. Any comments

 

Bwaaa .... your battery first needs to be charged up fully ... full powered batteries make upwards of 13.5. So 14.5 at 5K is not bad ... about right.
Cool.
Srinath.

 

battery is only 2 months old. Guess I will load test it tomorrow and see whats up. Thanks for the help.

 

looks ok to me too.

 

Yep, the guys are right. These bikes don't charge too much at idle. It is mainly due to the wide RPM range of motorcycle engines. Autos don't vary much more than about 2500 RPM while this engine idles at 1100 and at cruise is hitting about 5000. Higher the RPM the more the alternator rotor
can put out. The diodes are in the rectifer btw. There is a check sequence for it in the haynes manual and on the XJCD.

 

You should be cautious of overcharging or boiling your battery. I recall reading somewhere that over 15 volts at around 4500rpm indicates a charging issue.

Rob

 

I've heard that anything above 15V is bad too, but I had an 83 Suzuki GS750 before I got this Seca, and the published upper spec in the Suzuki manual was 15.5V at 5,000 RPM!!

And that sucker would reach 15.5V too! It would never go above 15.5, but it would indeed charge at that rate at anything above 5,000 RPM. I tend to be a high revver, so the battery saw 15.5V pretty much all the time I was riding, and I never had a problem with the battery.

Chad

 

The battery on my 82 750max seems to idle around 12.75, runs at about 14 and charges (i'm a high revver myself though) around 15-15.25.

Battery is less then two months old and I've tested pretty much my entire electrical system, being as I had a problem with it a few weeks ago...nothing out of the ordinary that I can see.

 

I read that the Charging issues (boiling Battery) is common on these and often due to connector corrosion. didn't believe it a first but found significant corrosion exactly where claimed. Boiling stopped.
Check ALL the connectors but especially any with brown red and or Black wires.. the One under the Tank is crucial. G'luck

 

It ain't just the volts that will damage a battery , at 14.75v but only charging at maybe 300ma-1amp or so will not damage it through cooking , 14.75v at 5 amp or more will and i think [but never checked the xj system] that is what the regulator on this bike does , it knocks back the current to a minimal amount. [one hopes]

Tecknikally 13.8 to 14.2 is "about" the correct maximum teminal voltage.

 

What you are looking for is an upper limit. If the voltage keeps rising with the RPM without leveling off or peaking then you have an overcharging issue. The top end volts on these bikes is around 15 so half a volt in either direction is nothing - if you see 17 volts at 8000rpm then something is wrong.

Good luck
Rob