gs550t with likely dead starter - preferred replacement?

[sacruickshank]

The starter motor on my '81 GS550T is likely dead. After several months of delays I finally put it all back together and hit the start button. First time it slowly cranked a few revs, the maybe one, now none...just the thunk of the solenoid activating.

The battery is new and charged, so I assume the starter motor has failed. I had it out for other purposes, but did not open it up to see if all was well. I'll double check the ignition system tonight with a car battery (car not running).

Assuming it is a dead starter motor, this raises two questions:
1. Service manual says cam chain tensioner has to come out, but that seems buried under the carbs. Do the carbs have to come out first, then cam chain, then starter?
2. If I'm not able to rebuild, is there a decent aftermarket starter motor for these bikes? if not, I'll search ebay/forums.

Thanks,

Steve

 

[Rich82GS750TZ]

The starter motor on my '81 GS550T is likely dead. After several months of delays I finally put it all back together and hit the start button. First time it slowly cranked a few revs, the maybe one, now none...just the thunk of the solenoid activating.

The battery is new and charged, so I assume the starter motor has failed. I had it out for other purposes, but did not open it up to see if all was well. I'll double check the ignition system tonight with a car battery (car not running).

Assuming it is a dead starter motor, this raises two questions:
1. Service manual says cam chain tensioner has to come out, but that seems buried under the carbs. Do the carbs have to come out first, then cam chain, then starter?
2. If I'm not able to rebuild, is there a decent aftermarket starter motor for these bikes? if not, I'll search ebay/forums.

Thanks,

Steve

View attachment 63538

1. If you can get a tool on the bolt on the inboard side of the cover enough to turn it it get it out, remove the cover. Then remove the thick wire from the solenoid attached to the lug on the starter motor, then you have to get a deep socket (10mm?) on the bolt (or probably 2) that mounts the rear of the starter motor to the top engine case, and I can't remember if there's 1 or 2 bolts, or maybe none near the outside end of the starter motor. Then to have push the starter motor toward the right side of the bike, lift up the back of the starter motor and move it away from the stator, up and out. After you've busted every knuckle on both hands and exhausted your entire vocabulary of swear word and even invented some new ones, to discover that that isn't possible because the cam chain tensioner is in the way, then you can remove the carbs, and then the cam chain tensioner.

Or maybe you'll be lucky and yours is one of the models where it is possible. I believe I have read of someone doing it, just don't remember which model.

2. We have a small local electric motor shop here that makes quick work of things like this. If it isn't possible, used ones pop up on ebay all the time. Lots of models share starter motors. Check cross compatibility.

 

[Baatfam]

Generally, the brushes are just worn out.
Clean up the commutator, drop in a new set of brushes, and Bob's your uncle.

 

[Brendan W]

It could be just the brushes in the motor.
Have you checked the condition of the main earth cable from the case to battery?
If you have a voltmeter put it between the case and battery when cranking.
Should be almost nothing.
Do the same with the supply cable and just because the solenoid is pulling in doesn't mean the contacts are good.
It's possible to extract the motor on the 850 without removing carbs or tensioner.
Bigger motor more room.

 

[sacruickshank]

After you've busted every knuckle on both hands and exhausted your entire vocabulary of swear word and even invented some new ones, to discover that that isn't possible because the cam chain tensioner is in the way, then you can remove the carbs, and then the cam chain tensioner.

Or maybe you'll be lucky and yours is one of the models where it is possible. I believe I have read of someone doing it, just don't remember which model.

Luckily I'm only holding the starter cover on with the single easily accessed bolt. I just put the carbs back on and the connection to #3 airbox boot is tenuous at best, so i'll try busting a few knuckles and see if it get lucky. Micro ratchets are my friends.

 

[1948man]

https://www.youtube.com/watch?v=ZlXuEbW0ML0

Rick's sells rebuild kits

 

[bonanzadave]

Not sure if your bikes starter is anything like mine but....

Heres how I removed, cleaned, and reinstalled the starter without removing the carbs.

tutorial starts at about post #10

https://www.thegsresources.com/_forum/showthread.php?253420-Something-s-gone-Haywire-(starter-)

 

[Redman]

When you said "had it all apart".... did you disconnect the negative battery cable from the back of engine and not reconnect it.....?

If so, the first time you tried to run starter it probably burnt up some of the small gauge ground wires with all that current, and then not work at all on subsequent tries.

 

[Redman]

https://www.stockers.com
Select Suzuki, motorcycle, year and model, and it will list all your options.
Although, they are in Calif, so shipping will be a few days for you.

THey have remanufactures starters. They operate on exchange, meaning, they send you a reman starter, then you send back your old one in the box, then they credit your CC with the "core" charge.

THey have brush kits also, and is probably all you need. Rebuilding that isnt hard, but does take some time and fussing. Will want to find some way to "dress" the commutator. I put some emory cloth on paint stir sticks and spin the commutator in a drill motor. Hey, goofey, yes. But it worked.

If you want to get the brush kit, you will need to remove your starter or somehow get an eyeball on its back end to see if is a Mitsuba or a Denso starter (could be either) to get the kit specific to that one.
If you are ordering a complete reman, it doesnt matter.

Brush kits are about 30bucks. Reman starter are 150 or 300.

 

[sacruickshank]

UPDATES:
1. When the bike was last apart I did not disconnect the battery ground to the engine, so that should still be as OK as a 40 year old screw connection can be. All voltages were ~11v or better when activating the starter button and checking against battery, engine, and ground screw.
2. I was able to get the rearward starter bolt out using a micro ratchet, but the front one is even harder to access due to the cam chain tensioner and limited space in the 550 engine.
3. Looks like the carbs have to come off which might provide an angle to remove the bolt without removing the tensioner.
4. thanks for all the input on brushes and sources. That will be my first test once I get the starter motor out.
5. Starter motor can come out with carbs off and cyl#2 intake off. Just barely fits past the cam chain tensioner if you try enough positions.
6. Test of the motor yielded one battery draining 5sec spin at low speeds. After that, nothing. Haven't yet figured out the correct prying position to get the end cap off and access the brushes

Pic shows inside, with some corrosion.

 

[sacruickshank]

I'm thinking those corroded brushes may also be a problem. I have a few spare and working starters from other projects, so I may see if parts are swappable.

 

[Baatfam]

I'm thinking those corroded brushes may also be a problem. I have a few spare and working starters from other projects, so I may see if parts are swappable.

View attachment 63545

Ya think?


Wow....pretty bad. Good luck.

 

[Grimly]

There's a good chance parts from others may fit. The Mitsuba 2-brush (and the four-brush) were fitted to a wide range of makes and models. I don't see them making brush holder plates specific to Zuk.

 

[Redman]

The problem of the "corrosion" there is that it looks like it could limit the travel of the brushes in its holder. (the brush needs to move freely so is pushed against the commutator by that spring).
Maybe it might clean up, and work better. But probably better to get a brush kit.

 

[sacruickshank]

Looks like the brushes and plate from a Denso starter from a Triumph Adventurer (on left) will likely fit in the GS starter. the plate itself is slightly different, but the OD and ID are the same. And the diameter of the starter commutator is the same @ 28mm.

 

[sacruickshank]

The brushes from the Triumph fit fine in the Suzi starter, which now spins nicely.

One question for those with more experience, is there any reason to avoid a light coating of grease in the shaft that sticks into the end cap, i.e. the opposite end of the spline shaft that engages the gears in the engine. I want to keep it spinning smoothly, but not sure if grease might mess up the electricals.

Thx

 

[Grimly]

Not 100% sure in my recollection of these specific starters, but it's common for that bush to be made of sintered bronze which has the property of absorbing oil and providing many years of lubrication when it's sitting in its own little enclosed space.

 

[sacruickshank]

UPDATE#N - Brushes from the Triumph starter fit well within the Suzi starter. Starter works when tested off the bike using a clamp and jumper cables from the battery.

But ... when I install the starter in the bike and send in the juice, you can hear freely spinning gears but not the pistons being cranked. All the gears are meshing correctly, so I did one test with the LH cover off. Low and behold the starter motor is turning CW when looking at cyl1! Could the Triumph brushes have an opposite polarity and cause the motor to spin CW? It's a three gear system, so the crankshaft will turn in the same direction as the starter motor.

I didn't take off the rotor or starter clutch. Could it have snapped? Should the large gear on the starter clutch be able to freely spin CW but not CCW?

Going back to my earlier pick, the brushes and power are in different relative locations. Would that make the starter spin in the opposite direction?

 

[Grimly]

Yep, the way to reverse a DC motor is simply reverse the polarity, and that's what's happened there.
It should be possible to find a brush plate that duplicates the original.
Try Stockers for a replacement.

 

[Redman]

.....
......
Going back to my earlier pick, the brushes and power are in different relative locations. Would that make the starter spin in the opposite direction?

Yes. Good troubleshooting, and good observation.

One brush has the positive power, and other brush is grounded.

Looks like maybe can move the positive brush just by putting it in the other. To move the grounded one would need to see if can find a way to ground that wire there on the other side.

or clean up original holder and see if better brushes fit.

or get brush/holder kit from Stockers