Less charge at higher RPMs?

[markus1]

So, a couple of mornings ago I went to start my bike (1988 vt1100c) which is always very cold natured, even when its not that cold. The 1st couple of tries it acted as it normally does, starts to fire and dies a few times before it starts up on the 4th or 5th try, except this time, it just quit trying to start. It still turned over but no fire...
After work that day i start the trouble shooting, and decide that maybe the battery was too low for a good spark. I put the charger on it and after the charger hit about 25% i tried it and it fired right up. I thought maybe it was an issue with the light bar on the bike and thought "ill just charge it over night, drive it to work tomorrow and figure out what the problem is later".
The next morning the bike started right up with full choke. While i was finished getting ready for work I heard the idle go down a bit, and thought the bike was warmed up so i went back out to turn off the choke which killed the bike... after that, again, it would not start sounding like it was again getting no fire.
Today I went back to trouble shooting. After charging the batter fully it was over 13 volts. The battery sat all day and never dropped below 12.8 volts. So I decided to check the charging system. I started with checking voltage at the battery terminals while the bike was running on full choke. it started around just over 13 volts, but after the bike warmed up a bit the charging went up to around 13.8 volts to just under 14 volts.
My bike has no tach, so I cannot tell what the RPMs are, but I noticed when I added throttle the charging voltage went DOWN instead of up.
The manual I have says at 5000 RPMs it should measure 15 volts. Yet mine is going down rather than up when I increase RPMs. I am planning to check the alternator and voltage regulator tomorrow once I have time, but I was wondering if anyone might be familiar with this issue?

*edit* Just noticed i never changed my picture from my 700 to the new 1100... I'll try to remember to do that soon.

[tcanthonyii]

What did it go down to? Was this with your lightbar on? If not restest with the lightbar.

Typically when this starts happening your regulator is going bad. Though as long as it stays somewhere over 12.5-12.8 ish you should be fine.

I just did the mosfet upgrade on mine b/c at WOT it was getting 12.2 ish.... 12.8 at idle.

[John Hopkins]

You may have a loose connection from the stator/alternator...left hand side near the battery plug/socket with three yellow wires...It's normal on an old bike to get a small dip at around 14.1 volts as the revs peak..if you get 14v and the connection is ok don't do anything until it gets worse..it's just fair wear and tear..

Considering those heath robinson T batteries it is a wonder the bikes charge at all..

John.

[markus1]

Thanks for the replies guys. I can't remember now how low it was going, it never made it to 14 volts, although it was close at idle. I don't think the charging ever went below 13 volts. After running for awhile with choke on, while i was revving it up, it started sputtering and backfiring and then died again and wouldn't start.
I did pull the fuse to the headlights and there was no change in the charging before it died.
I am about to put the charger back on it so I can continue testing, just to confirm I will try to start it before any charging, and then again once its charged.

*Edit*

Ok, I pulled the plug going to the stator. One of the contacts looks burnt, I tested across the connections with my multimeter and across the 1st pair i get .5 to .7 ohms, across the second pair I get .7 to .8 ohms, and across the 3rd pair I am getting over 1 ohm resistance, at times jumping up to 2 or 3 ohms.

I guess I need to check pricing on the stator.

[John Hopkins]

Before you do that bear in mind that not all multimeters measure exactly the same and the alternator is probably still ok..instead of measuring the resistance measure a/c voltage across any two wires, expect about 50v ac at tickover rising to 80 or 90vac at higher revs, there are three wires so that means three measurements...

disconnect the plug/socket start the engine, set the meter to 250v ac touch two of the wires at the stator side..the other side is to the reg/rec read the meter..repeat for each pair..

John.

[markus1]

Thanks John, I was actually just reading up on checking the AC voltage on the stator and am waiting for the battery to finish charging to test that.
In the meantime, I decided to test the voltage regulator, following the Haynes manual I found online. I checked the red/white wires for voltage (black wire on meter to ground) and there was voltage, the manual then says to check continuity between the green wire and ground. There are two green wires that go to the green connector under the seat and there is no continuity between either of those wires and ground.
Does that mean it's bad? Or, am I misunderstanding the manual? It says "wire" not "wires" so I'm wondering if thats a misprint or if I am testing the wrong wires. Should there be continuity between those wires and ground? I tested with the key off.

[John Hopkins]

Don't bother with the reg/rec just yet, I think you will find that is probably still ok..we call the haynes manual the Haynes book of lies..

the output voltage is the one you need to look at and depending on the condition of the battery you should expect about 13v at tickover and 14 to 14.8 at full revs...If the voltage exceeds 15 volts you need to replace the reg/rec.

John.

["Captain D"]

http://www.electrosport.com/media/pd...ng-diagram.pdf

Are you using this testing proceedure???
Haynes ain`t my source fer fixing nothing!!!
Good Luck,
"D"

[markus1]

I kind of wondered about the Haynes manual, I tried finding a clymer online (for free) but haven't been able to find one. I would buy a pdf copy, but I would rather wait and get a paper copy.
Still waiting for battery to fully charge. When I tested charging at the battery it was around 13.8 or so at idle and then down to just above 13, if i remember right, when i raised RPMs above idling with full choke. I have to tach, so I don't know what the actual RPMs are.
You have stated that my stator and voltage regulator are "probably" still ok. What else do you think it might be? The connectors all seem ok aside from the one wire in stator/regulator connection, that was somewhat burnt looking. last time I fully charged the battery and let it sit most of the day it never dropped below 12.8 volts so I think the battery is ok? It looks like a fairly new battery (i just bought the bike a couple months ago or so)
And just for clarification what exactly are you referring to as "tickover"? Im not familiar with that term.

Captain D, If I am understanding the troubleshooting flowchart correctly I need to replace my stator. I rechecked the resistance between the 3 wires (1 pair at a time) and if I just let the wires hang the resistance is around .4 to .5 occasionally going as high as .7. According to the flowchart it should between 4 and 6.

It's incredibly annoying all of the conflicting information you find about these bikes. I thought I got lucky finding that haynes manual so easily, but its telling me the exact opposite of what that flow chart says. According to it my readings are close to what they should be, but the flow charge says they should be over 4 times higher.

["Captain D"]

I dunno what tickover is either...


I`m hoping that the one fried connector is your gremlin though...
Good Luck,
"D"