Seca won't start and I'm an electrics newbie :(

So the solenoid just clicks when I hit the starter, no turnover. I tried a new solenoid because it was an easier thing to start with than tackling the wiring--but still just the click. Before the bike totally pooped the bed, there were two instances when I was out and it wouldn't start (again just the click), but after a few tries it got going. Then I parked it one day and couldn't get it to start after that.

So far I've opened and checked starter button/kill switch for corrosion and continuity, checked that there's current coming to/from the solenoid, put in a new battery and made sure all those connections are clean and tight. I do have the Haynes so I can definitely check the wiring diagram, but I'm so new to electrical stuff (and also completely daunted by it) that I guess I'm kind of just looking for advice on what to start with based on common XJ problems, so I don't go on a whole wild goose chase. I've been digging through past forum posts to see what I can turn up, but any additional input is much appreciated.

Oh also I replaced the 4 glass fuses with an in-line blade setup a few weeks ago, but it was being funny before the change so I'm ruling that out for now. I did have the ignition fuse wires taped together for a while because their connector broke (hence the eventual switch to the in-line fuses)...would that have made something wonky or caused a short somewhere? Again, I KNOW NOTHING AND I'M GOING TO CRY.

 

Use a coin or screwdriver to bridge the two large terminals on the starter solenoid. If the starter doesn't turn, then it needs new brushes.

https://www.xjbikes.com/forums/threads/replacing-your-starter-motor-brushes-w-pics.45727/

If it does spin then the safety circuits need to be checked, and maybe a few other things.
Which model of XJ do you have? They are not all the same, especially when it comes to the electrics.

 

What condition is the battery in?

also could need to just clean the connections at the battery, solenoid, and starter

 

New battery and the connections at the solenoid and battery are clean. I haven't checked anything with the starter yet.

 

I'll test the terminals and see what happens. Is it likely that the starter would go out after only 11k miles? That's what it has now but it was also garaged most of its life and I have no idea what the previous owners did with it. It's a 1981 XJ750 Seca.

 

Is it likely to bad with only 11k miles? I don’t know, but is 40+ years old too, so you can’t be too surprised if it turns out to be starter brushes or something

 

Can you bump start the bike?

 

You're going to get my stock answer to electrical issue questions. Get a wiring diagram - the correct one, for your bike. Read it, understand the bit you're working on. Get a dvm. Do some tests, job done in minutes.
Asking people thousands of miles away, who don't have a manual, or test readings is daft.

 

Solenoid clicking, with a new solenoid, but no cranking, means either the starter or the heavy connections to the starter (red wire to solenoid, ground to crankcase, etc). As was already suggested, try jumping the heavy terminals on the solenoid... if that doesn't crank (with your known good battery), then your starter is the issue.

 

Mine did the same thing when I got it… took the starter off, took it apart, cleaned the commutator with (I think it was automotive Mass Airflow Sensor cleaner … since it’s a milder cleaner than carb or brake cleaner) … wiped it off , put it back together and it’s been working great ever since

 

Starter brushes are a wear item. How quickly they wear is entirely dependent on how often the machine is started. I typically get 15,000 miles out of a set, but if the PO took a lot of short trips then the brushes would wear out faster.
It's an easy thing to check. Gather the low hanging fruit first.

 

Agree with that. As suggested, jam an old screwdriver across the solenoid. I would also suggest putting a light on - watch this at the same time - if it fails to crank over, and the light stays bright it’s the starter. If the light dims to nothing it’s your battery.