First bike, first (hopefully) minor electrical problem

dannyTheBoat

XS400 Enthusiast
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Hi everyone,

I'm new to this forum and totally new to motorcycles.

I recently bought the xs400 that you see attached as a starter bike to learn how to ride and how to wrench. The bike starts easily (kick only) and runs strong as far as I can tell. I went to take it our for the first ride today. Once again she started easily and ran strong. I went around the block twice then accidentally let it stall. After that it would not start again.

Back in my driveway, I noticed that the headlight wasn't working when it previously had so I figure my starting problem is probably, hopefully a fuse. I got in under the seat and checked the battery voltage, which was fine. The kill-switch gets the full battery voltage when it is off but only ~4V when it is on. I also don't get continuity between the + terminal of the battery and the kill-switch when the battery is removed. The causes that I suspect so far are:

- Groud fault somewhere
- Blown fuse
- Blew something in the rectifier/regulator, pickup coil, or the ignition coil

The only thing I can think of that might have caused this is that I was a little over excited and didn't let it warm up long enough, which may have over-loaded some fragile component. I never put much load on it going around the block though. I was hoping to get some riding in before I have to start pulling things apart, but here I am getting ready to take the gas tank off. The wiring schematic from the previous owner is attached. Any ideas on how to proceed would be great!

IMG_20190313_190448.jpg
MVIMG_20190317_141111.jpg
 
Welcome. So you get no power at all when you turn the key on? That sounds like a bad ground or blown fuse. A bad battery would probably still give a very dim headlight until the battery is completely drained.
 
Yeah no power to the headlight or brake light. Those are the only indicators I have. The last owner said he installed auto reset breakers in place of fuses but I haven't found them yet. I'll keep hunting. I can't think of why it would have started so easy for a week to go bad right away?

I'm hoping the voltage regulator didn't go. What a blue-baller . . .
 
It's a very cut up and modified bike so figuring stuff out will not be easy. It's also not the best setup for one of these, (mufflers/intake) Looks like it has a small battery on the bike somewhere as the stock box is gone. That wiring diagram also says 81 xs650 which has a different setup than our bike. This could be a long road for a good reliable bike. Hope you got a good deal on it. If you can't find fuses you may want to just start over with a stock harness and at least get a fully functional bike. Then remove any unneeded stuff after. Welcome to the forum.
 
I thought it was a good deal but now I'm starting to wonder. I've been chasing the wiring and testing voltages and continuity but no smoking gun yet.

You are right, there's a 12V LiFePO4 battery in there and what looks like the original ignition module, along with a relatively new looking rectifier/regulator and ignition coils. The connector to the pickups is pretty corroded and so are the power terminals so I guess I'll start there. The ignition module doesn't have any signs of failure.

Do you know a way to test if the pickup coils are good?

Thanks for your input guys
 
Ignition pickup and ignition coil testing/spec are in the manual which can be found on this site. There is no test for the ignition box.
 
I would suspect the PO installed auto reset breakers. Follow the red + lead from the battery until you find it. It really should be not far from the battery.
 
Start with the easy things, after all it was running. Presumably was running pretty well with responsive throttle, and died because you stalled not just random shutoff?

What is the battery voltage when off? What is it when key turned on so the signals are on? Do you have a battery tender Jr or something to jump off of to check? Might need to be careful with the tiny battery in there if jumping not to over supply it? (Hence battery tender Jr). If it's battery it's a not too expensive fix.

If it was regulator it may have cooked your battery (overcharged). Did you smell sulphur like rotten eggs at all on that ride?
 
Presumably was running pretty well with responsive throttle, and died because you stalled not just random shutoff?
Yes the throttle was responsive before it stalled, which I think was my fault, but I am very new to riding.

So far I have tested the pickup coils, which are within spec. I did find the auto reset breakers. They were so corroded that I thought they were terminal blocks, and the foam they are sitting on was damp. While its open I'm going to go ahead and map the circuits and replace the breakers. I'm hopeful that those are the problem since the head light and tail light both went out at the same time this problem started.

The battery was near full voltage and didn't seem to be damaged and I did get a charger for it. I have an electronics background so I have good shot at figuring this out and making improvements. Thanks for the tips. I'll post an update over the weekend when I have time to dig in more.
 
Good deal. Thanks for update and Godspeed. You probably know this, but 12V is generally not sufficient for 12V battery to E start. 12.5-13 v is Target range and shouldn't drop massively just from turning on before hitting start.
 
Update: I replaced the breakers and mapped the main power circuits, which match the schematic in the first post. The image shows the old breakers. I just mounted some new ones on a chunk of Delrin for a temporary fix. After that she started on the first kick and ran like a champ for my first hour or so ride!!

I am so happy and relieved; Definitely happy with the investment. Now I know what my first project will be: new electronics enclosure with a circuit re-work and a turn signal addition. If anyone has recommendations for a good, bright LED turn signal, I'm all ears. I would also love some tips for gas tank rust removal. I'll start a new thread to got on some cool upgrades. Can't wait to dig in and learn more!

For now, Its time to ride!!!

shitty breakers.jpg
 
Nice work. Proper battery voltage should be around 13-14v and I get about a 1v drop when I turn the key on.

Gas tank, you can use vinegar and some BBs. Let it sit for a while and slosh it around. Ive heard of others wrappping the tank in towels and tossing it in the dryer for a few minutes.

That wiring looks terrible.. what would I do? Id ride the bike the rest of the season and worry about it when I put the bike away for Winter lol. But the season is still very early so I might just rip it all out and start over.
 
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