Modern Vespa

Hello. So I was taking the bike to Toronto for a service and the battery died on the highway. The voltage meter on my usb charging port, in minutes, went from 12v to dead and so I had the bike CAA'd to the shop.

The mechanic said that the new battery which I had installed last summer
(Yuasa GYZ High Performance Factory Activated AGM Battery GYZ16H), which Fortnine, the company I purchased from, said was compatible with my bike, had too high cranking amps and every time I would start the bike, it would make the starter solinoid heat up like molten lava and ended up melting it.

I was reading about people here using Motobatt 20ah batteries on their scoots so is this battery I purchased truly the cause of that issue. Pic of the melted solinoid below.

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There is nothing about either battery that would mean "too high cranking amps" or would cause the starter to burn up. There was something wrong with the starter, or with the engine that overloaded the starter. Better find the cause and fix it before you buy a new battery. Is the engine seized? Is the starter relay stuck "on"?

Why didn't the fuse blow?

No the engine didn't seize and the starter relay isn't stuck on. I'll have to ask the mechanic why the fuse didn't blow. I didn't even think to ask that question when there but the fuse should have done it's job and blown to protect against that surge?

I would recommend you changing the mechanic as first step.

An electric motor, in this case the solenoid and starter, does not have an Amp consumption greater than it can handle, let me explain, a motor only "eats" what it needs, it does not matter if it has a plate with 200Kg of food (imagine Amps), if it only need 1Kg that is what it will use.

It is very likely that the problem is in your starter that is generating a short circuit and that is why it burned the solenoid. The starter could be lying down and bridging to ground. And yeah, it should have blown the fuse

Last edited by dariusz on Sun, 14 May 2023 22:01:27 +0000; edited 1 time

I'm looking at my bill again and what they replaced is the Starter Relay which is the part that I posted. This I take it is NOT the starter itself?

Correct, the photo is only the starter relay aka starter solenoid.

The starter itself is nothing more than a small high torque electric motor with a small tooth that engages the flywheel on the engine.

Also correct was the previous post re. excessive consumption by the starter and thus causing excessive draw (overload) on the starter relay/solenoid.

This is NOT a battery issue.

FWIW, here is a pic of a MP3 500 starter motor.

I have seen a few of those toast. could have been a loose wire connection that caused this. replace it. NOT A BATTERY ISSUE.

I have been running a 20ah battery now for over 10 years and never an issue.

also like others have stated electronic parts will only use what they use. they are not driven by what's AVAILABLE to use.

Change that mechanic PDQ, as he has eff-all understanding of basic electrics.

This is a known problem with that solenoid - the connections to your 'hidden fuse' (that connects the regulator to the battery) have overheated because they became corroded - because they didn't get a good slathering of dielectric grease early in their life.

Do an MV Topics search on "hidden fuse" (include the quotes).

The starter motor is fine.

Your battery is probably fine as well, even though it became fully discharged.

Sorry, wrong. The starter will be fine. It's that 'hidden fuse' fuse holder again, that prevented the battery from being charged.

BTDTGTTS: Another Fuoco hidden fuse story...

So I've done what you recommended jimc and thoroughly sprayed the Starter solinoid with dielectric grease.

Thanks for the help.