Modern Vespa

When I turn the key, nothing even turns on. No lights, no option to prep the bike.

I just pulled the battery fresh off the battery tender, installed it.

What could it be? Fuses? Relay? I'm not ruling out that the battery is failing.

How old is the battery?

Do you have a jump pack or a way of jumping the bike.

9- times out of 10 it is a battery issue
8 times out of 10 it is a connection to the battery issue
7 times out of 10 bad ground.
Verify the ground wires are tight.
In most cases there are 2. One to the starter, and another to the Case below the airfilter.
6 times out of 10 Kill switch
flick your kill switch multiple times, can even spray with contact cleaner. They are prone to corrosion on a bike that sits outside.
5 times out of 10 Start button. Do the same as above to the start button
4 times out of 10 it is a Brake sensor.
Check your brake light turns on when you pull the brake
Try both front and rear brake to start the bike
3 times out of 10 Antenna for the ECU does not recognize the key.
You will need to check the red LED on the speedo. you can search for what the blinking means.
2 times out of 10 your ECU has failed.
1 time out of 10 Your key has failed.

Good luck I was trying to be funny and helpful at the same time. These are all the troubleshooting steps I would take and in the order I would take them.

I had a similar problem with my GT200. But a GTS will likely be very different because it has EFI. On mine the headlight came on, bit nothing else. A jumpstart pack didn't help. The battery tested good, the kill switch tested good, the problem eventually turned out to be a broken wire inside the insulation on the wire that goes from the kill switch to the CDI, with NO damage to the insulation. I hope you don't have something like that.

Side stand folded in?
Kill-switch? (Switch back and forth several times to eliminate any corrosion)

Please explain what do you mean with "nothing even turns on. No lights, no option to prep the bike". Does "nothing" really means nothing?

Then check main fuses in battery compartment (Do not only check visually, better measure for continuity!)

Do you hear fuel pump when turning key to on?

Put a volt meter across the battery see what its pulling, If its showing a good 12 then try a drop test if it goes down check earth cable for poor or corroded or frayed connections.

Check the fuses.

not just the fuses in the glovebox. also check the fuse that's on it's own near battery (30amp iirc). there's another one else where too - check the manual for locations.

use a multimeter to check them - not your eyes

update: the battery was toast. swapped out a freshly charged PX battery from a diff bike and it started right up. ordered a new YUASA YTX14-BS and have had no issues.

thanks for the help squad.

And don't EVER leave a battery continuously connected to a battery maintainer, regardless of the manufacturer's optimism.

Jim knows more about this stuff than I do.

But I do what he says not to do on 6 bikes a year, all year long, and get 8+ years out of my batteries sooooo maybe just do whatever makes you happy

If you do this right from the start of the battery's life, you might get away with it. However, any battery that has been left to self-discharge for a while (and off-the shelf batteries even from Batteries Plus can fall into this category) then some sulphation will have occurred - even if only a small amount. If left on a maintainer this can warm up the affected cells - and the battery will eventually 'cook'. I've seen it so many times, especially when someone has brought in a battery from a nice cold garage (batteries prefer to be cold when left idle) into the warm and then put on a maintainer.

I have 6 bikes with batteries, and I have kept battery maintainers on them for the past 12+ years at least. I used to continuously have dead batteries because, having so many bikes, they would sit too long, and the batteries would go dead. The battery maintainers put a stop to that. All the batteries in all my bikes have been replaced, and battery maintainers have been used on them from new. Never had a problem. I did have a couple of the Deltran Battery Tenders fail, they used to be the best of the best. Now they are cheap (quality, not price) junk. I replaced them with another brand and everything has been fine. I would NOT leave anything connected to the battery if it is a lithium ion battery, like the Shorai, unless you want to burn your house down.

Thanks for the reminder, gotta ride the Sprint 150 tomorrow, it's been a few weeks.

That's what I do, though I guess when I buy a used bike (more on that later), I still do it anyway, and I doubt previous owners were as cautious as me... Still seems fine. Interesting read. Thanks for that. Reminds me of why you don't take something out of the cold and immediately put it on hot water.

To be honest, until last week I was only so-so on desulphating battery chargers. You might find this interesting:

I bought a used bike, the guy had charged it overnight on his El Cheapo Charger. I did a battery load test when I got home.

My load tester goes GOOD - OK - BAD. It tested in the low part of OK.

Hmm..

I put it on the desulphating battery charger for a couple days, took it off, came back and load tested it again, middle part of OK.

Repeated the process, two days later, the better part of OK.

I can't get that battery any better than that, but it was still interesting to see it gain some of it's old self back.

I've since repeated this test on my "bench test battery" that chills on the shelf 99% of the time, bringing back some of it's strength on the load test. Not enough that I'll want to keep it in any of my bikes, but still, pretty cool.

Food for thought, may want to add 1 desulphating battery charger to the rotation, see my previous post.

Like you I have a half dozen bikes I leave plugged in so as to avoid flat batteries (except for the lithiums which I maybe plug in once a week).

I'm not going to replace all my chargers with desulphating ones, but I'll rotate the desulphating ones around the fleet now that I've seen some nice results from them.

thanks to everyone for their assistance.