81 xs 400 special. Runs fine, but doesn't seem to charge.

[rescue50]

Hey all, I'm pretty new to bikes in general. I've picked up an 81 special in good shape. When using the kickstarter, it fires up and runs great indefinitely, as far as I can tell. It has fired up successfully on the electric start a couple of times. It seems though, that the battery is not being charged. There seems to be no difference between the low and high beams, and the turn signals flashed slower and slower until they would come on, but no longer flash. If I try to use the electric start now, the battery just clicks repeatedly, the way a dead car battery would. To be forthright, I should mention that the bike is not being driven, just idled and revved at a standstill, albeit for some extended periods (10 minutes am maximum probably.) like I said, it runs great, doesn't die out, but it does seem like I started with a good battery that has just been getting weaker and weaker. ( battery is new btw.)

Thanks in advance,
Noob.

 

[xschris]

Put the battery on a charger and see if will take a charge and hold it. Then with the bike running you should get 14.5-7 volts at 5k rpms. If not the bike is not charging. Being an air cooled engine I would not let it sit and idle for more than a few minutes without running it down the road. The bike could over heat. Also excessive idle time could foul the plugs and load up the engine with carbon.

 

[rescue50]

Thanks, I'll try that. Good point about the idling too. I hadn't considered the whole airflow thing...

 

[disfinado]

I'm having the same issue with a 1980 special. Would the voltage reading you recommended for a charged battery (14.5-7) be the same for a 1980?

 

[xschris]

Yes.

 

[rescue50]

Hi Xchris,

So it would seem that the bike is charging, I topped up the battery and at 5000 rpm read 15.1 volts. Would this indicate that the regulator is shot?

 

[xschris]

That's too high. You could fry components on the bike with that much volts.

 

[disfinado]

Thanks. I checked a manual I found and realized that after the post. I've gotta trouble shoot the charging system now. Wish I were riding instead.

 

[XSLeo]

Often under charging is a symptom of a bad regulator. Over charging is more often poor grounds on the reg/rec or low voltage to the reg/rec.
Regulators read the battery voltage to determine if the battery is low. Yamaha used a brown wire as a voltage sensing wire. With the key on check the voltage at the brown wire at the regulator. If it reads much below the battery voltage this could cause the overcharge. Lets say the voltage on the brown wire matches the battery. The reg will sense it has proper voltage and slow the charging.
If the brown wire reads low by say 1 volt the reg thinks the battery is low even if the battery reads ok. The reg thinking the battery is low by 1 volt keeps the charge rate high. 14.1 or 14.2 is ideal for a fully charged battery at 2000 rpms or higher. Add the 1 volt and you get 15.1 or so.
If the voltage on the brown wire is low there could be several places that could be the problem. Start at the battery. Follow the red wire to the main fuse. From the main fuse to the key switch, from the key on the brown wire to any other fuses.
Any connection along the red or brown wires, if weak can cause a voltage drop. The key switch is one place, where the key switch plugs into the harness is one, Any connector is suspect.
Leo

 

[rescue50]

Thanks a lot Leo, I'll check that this weekend.

Posted via Mobile

 

[disfinado]

Often under charging is a symptom of a bad regulator. Over charging is more often poor grounds on the reg/rec or low voltage to the reg/rec.
Regulators read the battery voltage to determine if the battery is low. Yamaha used a brown wire as a voltage sensing wire. With the key on check the voltage at the brown wire at the regulator. If it reads much below the battery voltage this could cause the overcharge. Lets say the voltage on the brown wire matches the battery. The reg will sense it has proper voltage and slow the charging.
If the brown wire reads low by say 1 volt the reg thinks the battery is low even if the battery reads ok. The reg thinking the battery is low by 1 volt keeps the charge rate high. 14.1 or 14.2 is ideal for a fully charged battery at 2000 rpms or higher. Add the 1 volt and you get 15.1 or so.
If the voltage on the brown wire is low there could be several places that could be the problem. Start at the battery. Follow the red wire to the main fuse. From the main fuse to the key switch, from the key on the brown wire to any other fuses.
Any connection along the red or brown wires, if weak can cause a voltage drop. The key switch is one place, where the key switch plugs into the harness is one, Any connector is suspect.
Leo

Good information. For my bike (1980 xs400s) it turned out that the regulator was not grounded properly. A wire was added as a ground from the regulator to the a good known ground on the frame. I used the ground on the frame where the battery grounds to the frame. Finding out that grounds are as important as power moving through the electrical system.

 

[fR3ZNO]

I've also been having some issues with my 81 special charging system.

When I first got the bike, it would only start when it was hooked up to the charger, so I picked up a new battery.

Then, the bike would start on its own, but the volts would slowly drop suggesting that it was not being charged. So I checked the stator, rectifier, and regulator using a multimeter. The stator checked out okay along with the regulator. But the rectifier was tested as bad with the diode tests. So I figured instead of screwing with a used unit, I'd buy a new aftermarket RR. Ended up buying one that's supposed to fit a bunch of different Yamahas from this time period. However, when I got it I ended up chopping the connectors off and soldering the originals on since the original units had a female plug whereas the new unit used a male plug. On the aftermarket piece, the plug that replaces the regulator only has two wires, brown and green, coming out of it. After looking at some wiring diagrams, it seems like that missing black wire that the original unit used was kind of important.

Here's the RR that I bought: http://www.electronicamotos.com.ar/products/Yamaha-XS650-Regulator-Rectifier.html

After wiring it up, the bike still isn't charging. So I'm unsure what I should do. According to the PDF on the link I posted, the RR is designed for the 650. But I figured it should work on the 400. So I'm starting to think I should pick this one up instead that has the correct plugs and uses three wires on the regulator plug.

http://www.regulatorrectifier.com/catalog/1981-Yamaha-XS400H-Regulator-Rectifier

Plus that one says it's actually supposed to fit my bike.

Anybody have any suggestions? Thought about making a separate thread, but I felt this was a related problem and to just post my question here.

 

[arfstrom]

I found this reg rec troubleshooting guide

 

[fR3ZNO]

Thanks for the PDF. I remember seeing that on Electrosport's website. I will have to print that out and give it a go.

 

[zonianbrat]

I too am discovering there is a charging system problem. Anybody discover an easy fix? I hate electrical problems. Not very good at troubleshooting them.

 

[fR3ZNO]

I too am discovering there is a charging system problem. Anybody discover an easy fix? I hate electrical problems. Not very good at troubleshooting them.

That's very vague. Haha. There's no such thing as an "easy fix" you just have to troubleshoot and diagnose the problem as best you can. Don't worry I get frustrated too.

 

[arfstrom]

I would start with the Drewpy re-wire, (Tech Tab, Top of webpage), Then while there, underneath all that, is 4 more links, based on key words, and such. One of them will get you bouncing down the road of discovery. (I have suggestions all over the website) I just primaryily recommend is do what is drewpy. (Granted untill you have figured out if the problem is what everyone thinks it is, you will have to validate your stator, Regulator, rectifier.

 

[zonianbrat]

That's very vague. Haha. There's no such thing as an "easy fix" you just have to troubleshoot and diagnose the problem as best you can. Don't worry I get frustrated too.

Yeah it is very vague. Apologies, I honestly do hate electrical gremlins and electrical problems! Figures I work at a power plant where we make electricity!! I am more mad at myself for not figuring this out before. We are at the beginning of spring and I thought I had it running and ready until this non-charging thing. We are going into an outage at work so I will be working 6 days a week for 6 weeks so I dont have much time to mess with the bike. I'm going to just have to do it in steps.

 

[fR3ZNO]

Yeah it is very vague. Apologies, I honestly do hate electrical gremlins and electrical problems! Figures I work at a power plant where we make electricity!! I am more mad at myself for not figuring this out before. We are at the beginning of spring and I thought I had it running and ready until this non-charging thing. We are going into an outage at work so I will be working 6 days a week for 6 weeks so I dont have much time to mess with the bike. I'm going to just have to do it in steps.

No worries, man. I was just saying it was vague and therefore it would be hard to help you out. but like arfstrom said, read the thread from Drewpy along with some of others regarding no charging solutions and just start from there. I'll try to find the link to a PDF that has a complete walk through on diagnosing electrical problems on a motorcycle.

 

[zonianbrat]

Hello again, I ended up buying another regulator hoping that it will correct the charging problem. I tested with the multimeter and wasnt getting any charge so I figured I would start with the regulator. Still working lots of hours so I havent had a chance to actually install it. My new question regards parasitic drain. The original start button apparently doesnt work very well. So at some point another owner installed another button on closer to the tach guage. It works ok although sometimes you have push it 2 different times to get a good start. The original starter button is still hooked up and it has in the past actuated the starter. Could this be a parsitic drain on the battery? How can I check?

Thanks