I recently bought a '90 Yamaha XV535. I cleaned the carbs and was able to start it. I then decided to pull the tank and flush it out, replace the fuel filter etc. While the tank was out I took the opportunity to weld a little tab that holds one of the side covers back on with a little flux core welder. At the time of welding the battery was out and all the connectors around the fuel tank were disconnected. Now I’ve put it back together with a new battery and everything works - except spark!
I’m here kicking myself really hard for being so stupid - welding with the ignition module still connected. But then I did some reading and most stuff suggests that just disconnecting the battery is enough.
I’m going over it again today cleaning and reconnecting all the connectors but I’d welcome any input. Have I fried my ignition or is there a chance it’s just a dirty connection?
That looks like exactly what happens when a connector has too much current passed through it, and it is not uncommon for motorcycles to suffer this kind of failure from loose/corroded connections. Unless you grounded your welder to one of those components instead of part of the frame near your weld, though, there’s no path for electricity through there from a welder. I still suspect you coincidentally found an existing problem, but fortunately all of those components can be fairly easily checked with a multimeter. Start eliminating possibilities with a wiring diagram for your bike, and a service manual, if you can find one.
You could be right - that connector is the only one in that bundle that I had not previously disconnected so I can’t rule it out as a preexisting condition. I’ll keep looking.
I did a quick search and found this manual. https://www.viragos.info/media/kunena/attachments/1518/1_pdfsam_manualdetalleryamahavirago.pdf
It’s usually pretty easy to find all sorts of service manuals, sometimes they’re scanned PDFs but better than nothing. I have one for my bike, my car, and my lawnmower lol
Try this link for a wiring diagram:
https://drive.google.com/drive/u/0/mobile/folders/13TttlH9fJnzFSQlDkB-GYDEXsNu7FPoe?usp=sharing