Starter problems


XS400 Member
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Hershey, PA
Hey all,
My first post on this forum and of course I’m coming to you with problems!
Bought my first bike, 82 XS400 Maxim, about a week ago for $750, with plans to restore it. Went and test drove it, everything worked, made the transfer and towed it home. Fired up reliably for the first week and then out of nowhere electric start stopped working. Turn the ignition to on, headlights come on, dash lights, etc but press the start button and nothing. I can tell power is getting to the button bc the gauge lights slightly dim when it’s pressed. Anyway, so my first thought is the battery. Take the battery to get tested and sure enough it needs to be replaced. Get the new battery, hook it up, gauges/Lights work, but still no electric start. Check all the connections, nothing jumped out at me. Opened the fuse box and found two blown fuses with my multimeter, the 20A main fuse and the 10A headlight fuse. Relaxe the fuses, get on the bike, turn the key and now no power whatsoever. I’m baffled. Anyone have suggestions? Thinking possibly bad starter relay or maybe even bad kickstand relay?
And to clarify, yes I used the proper startup procedures, so I’ve eliminated human error. Neutral, ignition on, clutch in, kickstand up, fuel on, kill switch off
Find the starter relay (usually close to the battery). When you press the start button, can you hear it click?
Wish I were there Pennsytucky, I love a good electrical challenge.
Your issue sounds easy to troubleshoot (if I was there).
It's simply a matter of electrons going here and there, or not.
Trying to troubleshoot over the interweb sucks at times.
Troubleshooting electrical is like math, there is no gray area, it either is or it isn't.
A starter circuit issue should be pretty straight forward (famous last words for electrical issues) as it is the DOHC bikes have the same as that for the late model SOHC bikes. Yamaha just renamed the Safety Relay the Starter Cutout Relay, other than that it looks identical. There are three switches, two relays, one fuse and a bunch of connectors. There is no kickstand relay or switch on these bikes.

The troubling thing is why the blown fuses? The problem may very well be in a different portion of the system. But, you have to start somewhere and logically work outward from there. If I am looking at electric start, I always use the starter relay as my first test (separates the starter motor from the rest of the control circuit) and work from there.
One other quick thought. Blown fuses indicate a short, perhaps in the headlight circuit. Giving the bike a good look over for wires adrift, worn off insulation and burned components is probably a good general thing to do. Since a lot of the lighting system wiring ends up in the headlight bucket, opening that up and have a general look around in there is a good first step also.
Also - wiggle the fuses some more.

The old glass fuse clips lose springiness and get brittle, leading to mystery electrical problems.
I looked at more the the factory manual info on the DOHC 400 last night and I found some confusing information, but also a potential lead to troubleshooting the problem(s) you are seeing. Here is a bit of background which is somewhat long, but explains some oddities in the symptoms you have. And changes where you should look next for issues.

The US vehicle regulations specified that motorcycles be equipped with always on headlights somewhere around 1979 or so. For the 1980 and later SOHC bikes, Yamaha used a headlight relay in US market bikes to meet this requirement. For these bikes, one leg of the alternator output was tapped and the AC current was fed through a rectifying diode and sent to the coil of the headlight relay. When the engine was started, the alternator began producing power, the half-wave DC current out of the diode fed the headlight relay which then latched in and turned on the headlight. On these bikes when you turn on the main switch, the headlight is off allowing more of the available battery energy to flow to the starter. After the bike starts the headlight turns on and remains on even if the engine stalls, or if the kill switch is used to shutdown the engine (because the headlight relay "latches" in).) US vehicle regs are satisfied. The start switch on these bikes is a simple two wire affair where the blue wire with white tracer (L/W) from the coil of the start relay provides a path to ground to let current flow through the starter relay coil and initiate engine start.

In looking at the DOHC bikes that followed on, there is no headlight relay shown in the electrical diagrams contained in either Chapter 6 (Electrical), or in the Appendix (Chapter 7.) It looks like the manual is for bikes produced for markets outside of the US because the diagrams show a manual headlight switch on the right-hand switchgear. However, there is a hint at how the US bikes were wired to give the automatic headlight functionality. On page 6-38 of the Electrical chapter is a "logic" diagram of the start switch. It looks like this:

There is an extra contact in the switch that when in the released position connects the red wire with yellow tracer (R/Y) from the headlight fuse to the blue wire with black tracer (L/B) which feeds the headlight. This provides the auto headlight without using a relay and is how I think your bike is wired. In this arrangement, when you turn the main switch to on, the headlight will come on. When you press the start button the headlight will go off to allow more of the battery energy to be used by the starter. Once the engine is running and you release the start button, the headlight with come back on and will stay on whether the engine stalls or you use the kill switch. US vehicle regs are satisfied.

This is also the place where two of your symptoms (headlight fuse blown and no starter motor operation) converge. So, I think you next steps should be:

1. Do the previous things just because they are pretty easy (check for clicking of the start relay and give the entire wire harness a look over to see if there is any roached insulation, etc.
2. Do what JPaganel suggests above ^. My fuse box was a complete disaster, and I replaced it as it is at the heart of the whole system. Make sure it and the fuses are mechanically intact and clean. You might want to consider upgrading it if you intend to keep the bike.
3. Unscrew the right-hand switch gear and look inside. Get to the plug that should be inside the headlight housing (it will have the L/W, L/B, and R/Y wires attached). This can be used for testing the switch contacts which we can go through next. See if there is anything funky going on with the switch or plug (carbon buildup, corrosion, melting.)

Very sorry for the really long post, but electrical problems usually come in twos or threes, so get ready to embrace the suck.
No need to apologize at all! I don't think I've had someone on a forum take so much time to try and help me out. I greatly appreciate it. A more mechanically and electrically inclined friend coming over tomorrow so we can work through the issue, using your suggestions for sure. He's restored several older bikes, so he's got a good eye.
Groovy! Be sure to let us know what all you look at and and find. I am really interested at this point even though I have never laid eyes on a DOHC bike. I hope you find the issue(s).
Oh also, I did find one other oddity in looking at the DOHC factory manuals - In the appendix there is a diagram of where certain electrical components are located and one of the components shown is a side stand relay, even though it appears nowhere on the various electrical schematics. So my flat statement that your bike does not have one may be completely wrong! Let the fun continue....
I don’t know what we did but we got the Maxim running. A lot of electrical contact cleaner, new spark plugs, and checking and double checking the wiring diagram. Ordering a new starter relay and new fuses to be safe.
Special thanks to Cap, we definitely used your troubleshooting tips along the way. At the end we said, “well, I don’t know what we did that ultimately fixed it but let’s crack a beer!”