How many volts are too much

[Laverda Dave]

Not sohc related but it is bike electrical related.
I was out earlier today on the VFR getting a bit of practice in for my IAM Observed Ride tomorrow. After 40 miles I parked up at Great Missenden for a cool down. When I went to restart the bike everything went dim and it refused to start, just the click of the solenoid. After a push it fired back to life as normal. I thought it was a classic case of a bad earth. When I got home I stipped the fairing off and cleaned up all the earth's and the starter motor feed.
The bike fired first time as normal. I then decided to check the voltage going to the battery from the regulator/rectifier. I am getting 18.5 volts something tells me this is way too much? From what I remember it should be between 14/14.5 volts.
Question is, is my rectifier/regulator faulty and would this cause the dead battery indication I had earlier even though the bike ran fine once bump started? It hasn't blown any bulbs either which I thought was an indication of a faulty regulator?
The battery though was warm when I got home but I thought this was hot air being blown over it as the bike was running between 90/100c due to heavy traffic.

[Moorey]

Your Reg/rec will have failed and cooked the battery. Same happened to me the last year on CB400sf.
Don't use as is or you could cause more damage.

[SumpMagnet]

I'd say that was too high....which would indicate the regulator has gone bye-bye. But the voltage should be measured across the battery and shouldn't go above 15V. VFR's do have a history of R/R issues....
The design is not a good one, and a combination of corrosion in the wiring, heat from doing it's job and age gets them all.

If your battery was being charged ( as it should..) then it will get a bit warm, and as it was a warmish run.

[sye]

VFR750's are known to have weak R/R's. I had two replacements on my FV before upgrading to a Mosfet unit. Check the connector and check for overheating signs and repair/replace as necessary. Replace the reg rec with either the upgraded Honda unit or replace with a Mosfet.

[matthewmosse]

18v, definitely too much in my books. I've seen the mess after a car battery I had on charge in the workshop burst. It split the battery along 4 seams, nearly split in 2. I was quite glad I wasn't around when it went pop, and that it just lost the acid onto concrete - I imagine it wouldn't have done anyone or any machinery any good to get a spray of acid. I haven't trusted my Optimate charger since. Must have been quite a bang given the splits in the battery case.

[Moorey]

Instead of buying a expensive Honda unit I bought  much cheaper copy direct replacement unit and put a 12v computer fan on it to give it a much easier life as it runs much cooler and a volt meter on the bars so i can keep an eye on it. 1 year on and it's still fine. The lot was less than £40

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[Bryanj]

A bad battery will also put the volts up, you need to do some proper testing in order

[Laverda Dave]

Thanks for all the replies.
I took the battery out this morning, it didn't actually slide out I had to wrestle it out because once it was out it was obvious it was toast and full of bulges, how it didn't pop I dont know. Mottobatt make a good battery though as despite being in the state it was in it was still reading 13.4v so internally it is still ok, no cells had broken down. Safety first though and I replacing it along with a new upgraded mosfet regulator/rectifier. I will test the stator output to be on the safe side. The PO had also had a problem with the oem regulator as the one currently on there is a pattern unit, shame the PO cut off the blocks to fit it with cheap and badly crimped bullet connectors. I have ordered a new block connector as well.
Hopefully back on the road next week depending on delivery of the new parts

[SumpMagnet]

Mosfets should be more reliable than the thyristors in the OEM