Starter Motor

About 2 weeks ago I was having trouble with spasmodic starting on my XJ900. I pinned it down to the starter motor...took it off the bike and opened it up and...filthy as hell inside. Carbon dust from the worn brushes blackening everything, including the commutator.

Gave it a thorough good cleaning and noted that I needed new brushes but figured I'd get another month out of them...hmmm.

Long story short, my local Yamaha shop had a pair that they sold me at a reduced price (must be the grey hair and the dejected look I had); headed off back to the bike after work, extracted the starter motor and took it home. Dismantled, cleaned, new brushes, taxi back to the bike, install said starter motor (just a couple of bolts), and...vroom...away she went.

And the moral of the story is this...might be a valuable regular winter service item to open up the starter and check the brushes and clean inside thoroughly. Once the carbon dust builds up and gets on the commutator the reponse from the starter motor gets weaker and weaker until...you're stranded 2 suburbs away from home!!

For those that haven't yet delved into the starter, it aint hard but you just need to make sure when you re-assemble that the brushes/brush plate go in the correct way and that the plate fits into its intended groove.

A clean starter motor is a happy starter motor and even happier non-stranded devoted XJ owner. Anyone with questions on starter motors, send them my way.

 

This is going to sound dumb but what's a "commutator"?

 

A former USSR spud! That's a sad bit of humor!

The commutator is a series of copper segments attached to the spinning rotor of the alternator. There is a space between each of the segments that isolates each copper segment from the two adjacent copper segments. The brushes then transfer the generated electrical energy to the rectifers and load of the charging system.

On the starter motor the commutator receives the current from the battery and transfers it to the rotor causing the rotor to spin inside the field windings, which turns the clutch, which turns the crankshaft which starts the engine of the motorcycle. At least that's the theory as I understand it.

Sometimes the spaces between the copper segments get full of dead brush powder, grease, and other debris, short together and need to be cleaned.

wamaxim

 

Sometimes just a good cleaning is all it needs. My brushes are still in spec so I just cleaned things up and put'r back together. Brushes are cheap, so don't be afraid to replace them if they are wore.

 

Great description of the commutator and the inner workings of the starter motor.

Yes...brushes are relatively cheap and it's worth a once a year check to make sure they are in spec. And at the very least a good cleaning on the inside of the motor. Despite O rings etc, my starter motor on the inside every time I have opened it up was full of dust and grime. The worn brushes leave their residue as well and I reckon if some of that dirt and moisture start gumming up the insides it impacts on the durability of the brushes; i.e. with some moisture or oil that might penetrate into the motor over time actually have the effect of softening the carbon brushes?

I don't know but it seems plausible. Maybe one for the XJ Mythbusters.

 

whats the best way to replace the brushes? i already did mine but i want to make sure that i did it correctly...

i clipped the copper braid that connects one of the old brushes to the ring. I did this because i could not manage to pry up the bent tang that holds the copper braid.

I then soldered the new brush braid on top of that tang.

is this correct? is there a better way to do this?

 

bump?

the starter works, and turns forward.... does this mean i did it right?

 

Sorry Potatoes. It sounds like you did it right (I would have done the same), especially since the motor didn't smoke when you tested it out.

 

awesome thanks robert. just needed a little encouragement

i got a little worried coz i read "electronics for dummies" and found out what a cold joint was/how not to solder... and it seems like i did alright, though i might have a cold joint... we will see

thx again

 

Secret to avoiding a cold joint is to heat the surfaces until the solder melts on the surfaces. Don't feed the solder onto the iron. Keep teh joint still until it cools to avoid a fractured joint.

 

Excellent advice Bill.
Whenever soldering hold the solder on the oppisite side from the iron.
When the piece heats up enough the solder will flow toward the heat giving you a good solder.
When sweating copper pipe with a torch same applies.

 

Oh man, I'm stoked. I'm gonna do this to my starter today when I get home from work.

Here's what my brushes currently look like.

 

Where can I buy new starter motor brushes at?

 

We have them in stock, drop us an e-mail or PM and tell us what bike you're working on.....

 

Just sent ya a PM chacal. Thanks!

 

a local altenator and starter repair place put a set in for me for 20 bucks brushes included. I went threw that last season. it was cheaper for im to do it tan I could find and have brushes shipped to me.