Starter very weak

1984 VF1000F

Riding the other day I came to a stop and shut the bike off. Wouldn't start after, the starter couldn't turn the engine fast enough. My buddy came and jump started me (worked fine) which got me home where it has sat since.

Went out today and tried to start it after sitting on the trickle charger for a week. Turned over ok but on the slow side, and never started. Got a spare truck battery I have charged on the shelf (don't ask) and used it to try and jump the bike. No go. At this point only the relay is clicking on properly.

Get out my DMM and find 12.5v at battery, with the starter button depressed I have 12v all the way to the terminal on the starter.

I removed the starter and hooked it up to the truck battery with jumper cables, it spins over seemingly ok but I can't test how much force it is actually generating just that it spins. Also the starter seems to spin freely with my fingers.

Re-installed the starter and tried to start the bike again. Turns over, very slowly and briefly before stopping completely again. Taking the truck battery straight to the starter yields a decent spark when contact is made with the +'ve lug and a very slow spin of the engine.

I put it on its center stand and tried turning the rear tire in fifth gear. Engine turns over about the same as I remember when doing the valve adjustment and turning the engine with the rear wheel so it is not seized.


So my question is....

Do these starters fail in a way that they get extremely weak under load? Or is there something in the starting gear/system that could be fucked leading to this seemingly binding up system?

 

Sounds like the brushes are worn out. Making enough contact to spin the starter but not so much when under load.

 

I can't argue with that.

Any other opinions? If not I will either try and find a used one, or get this one rebuilt. I see there are rebuild kits on ebay, not sure if it is pretty easy to do at home without any press or such for swapping bearings.

 

Brushes was correct. The -'ve brush was out of place and not making contact. I cleaned it all up, tweaked it back into place and lubed the bearings. Cranks over harder than any other time i've owned it now. Hopefully the fix lasts.

 

Cool, glad you got it sorted. Especialy without having to buy replacement parts. Can't beat that!