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-   -   Not enough voltage??? (https://www.vn750.com/forum/19-electrical/104039-not-enough-voltage.html)

loneWolf 05-18-2019 02:07 PM

Not enough voltage???
 
Looking for a little help, ok here’s the deal. Recently purchased a motorcycle that was sitting for years. And it don’t seem to spark on all cylinders like it should, unless I have jumper cables hooked to it from a running car.... battery is fine! Tried 3 battery’s two was new..... I can start the bike by jumping it off a vehicle. And I’m able to remove the jumper cables after it starts and it will still run. However I’ve not let it run for more than a minute.... next thing I noticed is someone has put a voltage meter on the bike and it always stays one mark below the green light unless jumper cables are hooked to it..... if the green light on the meter lights up green I get perfect spark! But however if not only front cylinder gets spark... I’ve also noticed when I hit the brake handle with ignition turned over the voltage meter practically drops to nothing! Now if I have jumper cables on like I mentioned the light on the voltage meter is green until I hit the brake handle then it drops a mark below green and won’t start.... sorry for all the confusion needed to pick at someone’s brain other mine... what could the problem be? P.s. the old owner said he was driving it down the road one day and it just started to cut out. Pulled it home and that’s where it sat for years

TonyO 05-18-2019 02:46 PM

Sounds like stator or the regulator/rectifier is iffy. I would guess the R/R based on symptoms

If you have a multimeter its easy to check the stator output. Should see ac volts at each of the three yellow wires heading to the R/R, test with the R/R disconnected!

VN750Rider/Jerry 05-18-2019 03:13 PM

With the jumper cables disconnected and the bike running, use a multimeter to check the voltage across the battery terminals at idle. Then rev it up to 3000 RPM. You should get around 12V at idle, and over 14V at 3000 RPM. If not, you definitely have charging system problems. A car battery also has around 12V with the engine off, but a car has a much stronger charging system than any motorcycle. So it is likely the cars charging system that is making the difference.

BTW, it has long been said that it is not a good idea not to use a running car to jumpstart a motorcycle. I never though much about it, but I don't see why not. The cars charging system put's out the same voltage as the bikes, it is just capable of a lot more amperage. And the motorcycle will only draw the amps it needs.

loneWolf 05-18-2019 04:37 PM

I’ve never worked on a motorcycle but have worked on atvs for years. Surely a stator wouldn’t cause this problem? But on the side note the old owner did say he replaced that. And I’d imagine he did since he has cylicone ran around the case... it just appears to me that say if all the lights on the bike was off. I’d bet money it would fire right up. And on another note sometimes using jumper cables won’t always get that green light to fire the bike up. Sometimes I have to let it sit what seems like forever... I’ve also noticed someone’s tampered with some wiring. Don’t look like anything serious. I’ve never had to deal with a failing r/r so you think this will be the problem for sure?

loneWolf 05-18-2019 07:36 PM

So I tested it. Battery is around 13.30v even at idle when I rev it goes up for split second then back down. It seems to fluctuate

Jason Pittenger 05-19-2019 10:08 AM

I would replace the R/R with an aftermarket.

loneWolf 05-19-2019 03:37 PM

10 Attachment(s)
Ok so I used my voltage meter at 20k ohm setting and tested the wires on stator. Each one shows 001..... upon inspection I noticed the stator plug was cut and wired direct to the wireing harness..... so I got curious and pulled the side cover of motor....( just the part to where you can see the stator) and I had found that someone made a plate and put in to hold the stator? Some homemade job for sure.... so I’m ASSUMING they cut the plug off the stator because it wouldn’t fit through the hole on the side cover where the black rubber piece normally sits to seal the oil in... so I guess what I need to know now is- is the stator good at 001 ohms? I would expect it to be around 003-004.... but once again I know nothing about a motorcycle 🙂. And pics will be added, I sure could use as much help as possible and really appreciate everyone that has gave advice I really do. Thank you all. Ps. I added photos of the voltage thing I ramble on so much about, needing to be green to get it to start up. When on orange/yellow it won’t fire good enough to start. To make it green I gotta slap on some jumper cables. When bike runs it goes from green to the mark below it just kinda jumps around.... would the metal plate the guy added be creating this whole problem?

TonyO 05-19-2019 04:08 PM

The looks like a version of the "Tuxedo Mod", named after the member of this forum that came up with it. It enables the stator to be replaced without pulling the engine.

Stator windings are a couple feet of wire wrapped around an iron core so 1 ohm is good. Check no shorts to groubd. I still say you have a R/R problem and maybe a battery issue.

These bikes will not start if the battery voltage is low, even if it cranks the ignition module needs 11 plus volts to fire correctly.

Check the dates on the "new" batteries as they can sit on the shelf for a good proportion of their life. If they drop below 9 volts EVER then they are trashed. They may still show charged but will rapidly discharge under load. Make sure the battery is an Absorbed Glass Mat (AGM) type, they work better and need no maintenance.

You should see 14.5 to 15v charging at RPM's.

loneWolf 05-19-2019 04:39 PM

The mod is very interesting, nice job to the person who came up with it! And how do I check for shorts? And also the battery is for sure good I even swapped some out of my quads still get same problem. As soon as I turn the ignition switch over my little voltage light won’t go to green.... yesterday I had hooked my voltage meter to the battery it showed somewhere over 13.20. Unless I hit the brake handle then it went down a lot. But anyways with the bike running the voltage was jumping around, even at 3k rpms I believe the highest my meter showed was 13.40-13.50 somewhere in that range. I’m overly excited to get this bike running so I can drive it around my little town. I’m not 100% on how the r/r works but I’d say that’s the problem would it not let my little voltage light turn green when I turn the ignition switch to the on position? I just figured the stator and regulator would only affect the bike while it was running

Mr. spock 05-19-2019 04:47 PM

Dumb? question
 
Not sparking (normally)? Pick up coil? AKA, pulse generator?


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