Kawasaki VN750 Forum banner

1 - 20 of 59 Posts

·
Registered
Joined
·
46 Posts
Discussion Starter #1 (Edited)
Hello, got a 99 Vulcan 750 that had a dead battery. Selling this bike to a friend, I let him pick his new battery. It was a $38 battery off of walmart.com

I got the battery shipped to my place, threw it on the trickle charger and made sure it was full. Then I installed it on the bike and viola, the bike started like a champ.

My friend comes to pick up his new bike, 20 min of riding and he's not quite home... he stalls and the bike won't start. Battery appears to be dead.

He let's everything sit for 10 min and all of a sudden the bike "wants" to start but doesn't have enough to turn over. This seems weird to me, how did it go from completely dead to kind of dead? Overheating issue or something?

He ends up pulling the battery and bringing it to AutoZone to charge a bit, gets home, charges the battery up and goes riding to work a few days later... all good thus far, got him to work.

Now it's time to leave work and he attempts to start the bike a few times... not enough juice to start the bike.

So I'm at a loss. All due to buying the cheapest battery he could find? Charger issues?

He did the volt test... battery was around 12v when fully charged... he said it was 11 something when the bike was running. Sounds to me like the charging system is failing but even then... the battery is only good for a 10 min ride without being charged????

I saw a few sticky threads about how to test certain stuff but they are either missing the photos or the thread has changed since 2012 so we're stuck!

Any help is appreciated.
 

·
Registered
Joined
·
46 Posts
Discussion Starter #3
Thanks for the reply. Any way to properly test these instead of blindly buying them?

I watched a few videos of stator replacement... seems like quite a job.
 

·
Registered
Joined
·
8,337 Posts
Thanks for the reply. Any way to properly test these instead of blindly buying them?

I watched a few videos of stator replacement... seems like quite a job.
It's not too hard to test if you follow the steps, either in the threads about it or the repair manual that you can download. Link is around here somewhere. Bear in mind, on the stator voltage you're looking for AC volts, not DC.

I also think the charging system needs tested, but have zero faith in the small wet cell batteries from Wally. Had a mower that used a motorcycle sized battery, and Wally's would hardly start an 18hp Briggs twin, always ended up jumping it, a lot. A near dead car battery started it better.

Did Autozone load test the new battery?

"Around 12v" ... 12.1v is pretty much dead. Need to see at least 12.5v, but 12.6v and higher is always better. After a fresh charge, a new battery should be near 12.8 or higher.

Maybe wally will take it back for purchase of an AGM type, pretty sure they have them. AGM type tends to rest near 13v.
 

·
Registered
Joined
·
46 Posts
Discussion Starter #5
Thanks for the replies. My friend will be buying a new battery and we'll do a proper test on the battery and move along to the charging system as needed.

Although the cheap Wally battery is an AGM... still seems untrustworthy at $38.
 

·
Super Moderator
Joined
·
2,570 Posts
there should be a manufacture date code on the battery, check it. I have found new agm batteries at the big box stores that were already 3 yrs old! Last time I changed batteries, I dug thru no less than 6 before finding one less than a year old
 

·
Registered
Joined
·
46 Posts
Discussion Starter #7
I'm going to get the bike back here so I can test stuff. I'm actually starting to think my old battery (that I thought was dead) is actually fine.

It was at 11.66 V last night so I threw it on the trickle charger. This morning it was about 14 V while being charged, 12.8 V when I took the charger off.

I really want to test the R/R and stator but all the threads I'm seeing here are really old and all hosted pictures are gone. I'm no expert with electrical and just don't understand what to test.
 

·
Registered
Joined
·
46 Posts
Discussion Starter #8
Here is what I found regarding testing the stator. Any further advice to help with this? I literally don't know what this means, pics would be amazing.

lets call the three yellow wires A, B, and C
Bike off
A:. resistance (case to stator wires),
A_______ohm, B________ohm,C_________ohm

B: resistance (between the three poles)

AB______ ohm, BC________ohm, AC________ohm

C: AC

Bike running
C: ac volts (between the three poles)

AB_____acV , AC ______acV,BC________acV
 

·
Registered
Joined
·
1,355 Posts
Well, I don't have pictures, but if you look at the wires going from the stator to the R/R, you'll see that there are just three yellow wires. Each of these is one third of a 'Y' shaped circuit coiled around the stator. If any one of these coiled branches of the circuit gets grounded to the housing, you're going to short out the stator. If you short out the stator, the problem leg will likely burn out and cause an open in the circuit (no electricity will flow past the broken wire).

Measuring the resistance from each leg to the case (part A) will tell you if you have a short. All these values should all show infinite resistance. (edited: should not have a low or '0' value, which would indicate a short)
Measuring the resistance between each of the three legs (part B) will tell you if you've got a broken wire. All these values should be non-zero, and close to the same value between any two legs.

With the bike running, but the stator unplugged from the R/R, you should get an AC voltage between each of the legs. This voltage should be greater than 14v, and should be close to the same value between any two legs.
 

·
Diesel Tech
Joined
·
136 Posts
Another thing to check is voltage ripple. Set your multi-meter to measure AC and check voltage at the battery with the bike running at 4000rpm. You should have less than 800mv AC voltage (ripple). More means you have a bad stator leg or R/R.
Permanent magnet alternators like these are always going to have a lot more ripple than a field controlled alternator like in cars.

 

·
Registered
Joined
·
46 Posts
Discussion Starter #12
Well, I don't have pictures, but if you look at the wires going from the stator to the R/R, you'll see that there are just three yellow wires. Each of these is one third of a 'Y' shaped circuit coiled around the stator. If any one of these coiled branches of the circuit gets grounded to the housing, you're going to short out the stator. If you short out the stator, the problem leg will likely burn out and cause an open in the circuit (no electricity will flow past the broken wire).

Measuring the resistance from each leg to the case (part A) will tell you if you have a short. All these values should be 0.
Measuring the resistance between each of the three legs (part B) will tell you if you've got a broken wire. All these values should be non-zero, and close to the same value between any two legs.

With the bike running, but the stator unplugged from the R/R, you should get an AC voltage between each of the legs. This voltage should be greater than 14v, and should be close to the same value between any two legs.
Thank you very much! I'll test this as soon as I get the bike here.
 

·
Registered
Joined
·
46 Posts
Discussion Starter #13
Another thing to check is voltage ripple. Set your multi-meter to measure AC and check voltage at the battery with the bike running at 4000rpm. You should have less than 800mv AC voltage (ripple). More means you have a bad stator leg or R/R.
Permanent magnet alternators like these are always going to have a lot more ripple than a field controlled alternator like in cars.

Good to know, thanks - will test.
 

·
Registered
Joined
·
46 Posts
Discussion Starter #14 (Edited)

·
Registered
Joined
·
795 Posts
If you're gonna go ahead and solder in a replacement, which appears to be necessary, you would be best off to iunstall a MOSFET or series style R/R. Lots of info on the forums here on how to find, wire, and install those.

While you're here, though, you should use a multimeter to see if you get good voltage across the stator wires
 

·
Registered
Joined
·
8,337 Posts
x2 on a MOSFET kit, easy to wire up and eliminates all the stock R/R wiring and plug.
 

·
Diesel Tech
Joined
·
136 Posts
3X.

Its overkill for the wattage of this system, but that means it will be less stressed and work cooler.
 

·
Registered
Joined
·
46 Posts
Discussion Starter #20
Did the tuxedo mod, got everything back together and now the bike doesn't want to start :/

It tries to crank but won't start. The bike was always a little stubborn when cold but I don't think this is just being stubborn, it will not run.

Would anything done in the tuxedo mod make it not start? Even if the stator or RR was a bust... those are just for charging right? So no idea why it suddenly won't start.

1 thing I'm not 100% on is the 2 connections next to the stator, does it matter which position they are in? Meaning if I bolted the top one back in on the bottom, is that a problem? I took a pic of their positions prior to taking out but my phone didn't save the pic.

Any other ideas?
 
1 - 20 of 59 Posts
Top