Slow Cranking from 1985 Spree Electric Start

[pprice]

I had a different post on this a couple of months ago that seems to have died. Anyways, I am having issues getting my spree to start with the electric start. The starter motor cranks over very slowly and doesn't spin the motor fast enough to start.

Some info:
-The battery voltage drops from 12v to 9v initially when the starter is pressed and then continues to drop slowly while the button is depressed
-I've tried jumping the battery from a car battery with no luck, so it's not lack of power from the battery
-The starter pinion is lubed and spins freely
-Side cover gasket is installed to prevent pinching of the pinion
-The starter relay gets decently hot after cranking for 5-10 seconds
-Spree starts fine when the engine is cranked over with a drill
-I took the starter motor apart and everything is clean and looks fine
-Starter spins nice and fast when not installed

Can the starter motors lose power over time? I had plenty of trouble finding my current starter motor (didn't come with one) and don't want to go through that again.

It would be nice to get it up and running reliably now that its really nice out.

Thanks in advance for any help!

[Ultraliner]

Hmm have you tried measuring the voltage at the battery terminals with the jumper battery connected and the scoot trying to crank? If the voltage is still dropping to 9V then i'd say your jumper battery is suspect. Voltage should still be up over 12V while cranking and around 13.7V idling/running.

I guess if the starter motor had a few shorted winding turns it wouldnt operate at full speed and would get hot, also causing the starter relay to get hot pretty quickly due to the increased current... But this is kinda unlikely. Did the starter smell burned or did any of the winding insulation look vastly different to the majority when you had it apart?

Check the voltage as described above and report back

[pprice]

Measured the voltage while jumping. Started at about 13v and dropped to 10.5v while cranking. I'm jumping from my car battery and I drive the car everyday, so I know that battery is good. Starter and starter relay still got pretty hot after trying for about 20 seconds (with some breaks in between pushing the starter) and it seems to crank slower and slower the hotter it gets. If I let it cool down for a while, it then starts cranking quickly for a bit, but then gets hot and slows down right way.

Nothing looked burned or smelled burned when I had the starter apart. Everything looked pretty normal to me. I might look into having the starter motor refurbished.

Any other suggestions of things to try are welcome!

[pprice]

Brought the motor to a repair shop and they said the armature was burnt out and I'm looking to see how much it is to rebuild.