charging problem again?

my battery died last week (starting problems over the past month and final bike stop/failure on the road - i was on the way to 1800km trip). i called my girlfriend to remove battery from Z750 and bring it to me. whole trip then ended without any more problems with this "backup".

i was curious, if the only problem was the battery. so i checked today with the service manual and did the battery/ignition system tests with multimeter (i did it with the battery from Z750 - i still don't have new for VFR).

there are the results (results are quite the same with all the lamps on or off):
1) battery voltage is cca 13.1V with ignition off.
2) battery voltage is cca 14.5V+ on idle.
3) battery voltage is below 8V on 5000rpms! falls linear with the increasing rpms from 14.5V on idle.

how can the bike run with this? shouldn't the ECU be already powered off with so low voltage? how is it possible, that the bike did 1800km trip with many starting sequences and all the lamps on? and the battery still gives 13.1V.

mk

 

My first suggestion is that the regulator/ rectifier (r/r) is toast. Get a new one. The second is check the stator. It may also be fried. And most likely the batery is probably no good now either.

 

Oh man, I feel your pain. What a headache. I also would check your stator and RR. Unfortunately you have to buy a new RR to see if that was the culprit. Buy a new battery and RR together because if one thing is bad it will possibly cause the other to fry.

Use this fault finding diagram to help you a little. DL the PDF. (scroll down on the page).

http://www.electrosport.com/electrosport_fault_finding.html

 

if i go through the PDF, everything should be ok, because:
1) below 2500rpm the voltage is above 13.5V
2) then rev to 5000rpm and voltage should be below 14.8V and this is (8V)

i'm going to check at least the RR and the alternator charging coil.

regards,
mk

 

A cheap way to find the problem is go to a used bike sop and get a rr from say a 300 ex quad or whatever just match the wires and try it,I have had a 300 ex rr on my bike for 5 years now,Igot tired of buying the crap aftermarket units for 150.$35 for the quad rr if it does go out big deal go get another,Ialso mounted the rr under my headlight and off to the side on the inside of fairing now when running i can hold my hand on it,try that on the (cooler running) models for 150 dollars.Its a ghetto fix but it works nonetheless.

 

Generally, anything above idle should read higher than 13.5. You originally said at 5000 rpm your votlaghe was below 8 if I read it correctly. This is indicative of a faulty r/r. The stator should read volts AC and should increase as the engine revs. It will probably not ever reach 75 volts (as has been explained to me), but the voltage should continually rise. If it falls off at any point, then the stator is faulty. I suggest you replace the r/r and the battery at the very least.

 

Hey MK01; I have a Y2k VFR 800. I just swapped my original R/R for one of the new improved heavy heat sink units from Honda. I will sell my old unit to you $50
American, plus freight charge. The orig. one works fine , I changed it because I wanted the reliability of a new one . But honestly the old one workes just as good as the new one. eddie

 

lucky day for me.

i dismantled the 3P (alternator) and 6P (RR) connectors, did the measurement. everything was ok, so i used WD40 on all contacts, plugged in and did the measurement on the battery. now i have 14.1V with hi lamps and within the whole rpm range.

thanks everybody for support, answers and .pdf.

to eddie: i hope, i will not need new RR for a longer time now

 

I hope you have good luck with that. From past experience, r/r's are hit and miss, meaning sometimes they work, sometimes they don't, until they fail altogether. I had that problem with mine. I thought the r/r went bad last september. Turned out the 3P connector had melted and the wires burnt. Fixed it, bike ran fin until the end of december, when it did the same thing with one exception, after fixing it again, I got wierd voltage readings: 13.5 at idle, 14.5 between 2 - 3K rpm, 13.5 3k rpm and up. It did not however fix the problem as it left me stranded in Daytona. Fortunately I was close to a bike shop and was able to get a battery (and a tow from Dad). Stil had the wierd voltage issue tho. In March, I ended up replacing the stator, which I thought would solve the problem. Nope, 3P connector melted again. So I replaced the r/r, relocated it to the underside of the subframe, and bypassed the harness by running my own wiring. After that, I never had a charging issue. You might be just fine, and I hope you are, but keep an eye on it.

 

My old Sabre did the same thing as yours. I just cleaned the plug to the r/r and added some dielectric grease to it, and it has worked fine for over 8 years. I think you may have found your problem.