Trouble getting bike started

[Benjisus]

Hey everyone,

Ive been working on my 1979 GS 750 throughout the summer, finally got everything put back together, went to start the bike, and the battery lost power within seconds. I just had the battery charged and confirmed it is good.
Now I did change the battery on my bike to a much smaller battery here. Of course i smaller battery like this is going to die quicker then others if the bike takes a minute to start... but it stopped so quickly there has to be another issue..
Once I saw this happening I hooked the bike up to my car battery just to see if I could get it started.. nothing.. the bike turns over for a few seconds and then goes quite and just hums.

My knowledge of electrical is pretty minimal.. So any information is much appreciated! And if there is anything else that you guys need to know to help diagnose im happy to give.

[Rijko]

did you hook it up to a running car ? (DON'T)

Where's the humming sound emanating from ?

[Benjisus]

No it was definitely not running, I at least know that about electrical
The humming sound seems to be coming from the engine block? Im not near the bike at the moment, but last night it seemed like that was the location of the sound.

[Rijko]

ok, good
We've seen several fried electronics before because of a running car jumpstart.

That humming sound is strange. If it comes from the engine (and not the solenoid) it may be the starter motor does not have good ground, is not able to draw enough amps through the clamps, is dirty inside, or has another issue.
Or the engine somehow stalls because of a mechanical problem.
Let's see where the humming comes from first.

Do you have good spark when it does turn over ?

[Benjisus]

Oh i can only imagine.. haha

Yeah again sorry im not exactly sure where it is coming from exactly, in my mind the solenoid definitely makes more sense.. so once I make it home I will figure out exactly where its coming from!

Yes, the bike will turn over for about.. maybe 10 seconds before the turning over comes to a stop, and its just the humming left over..

[tom203]

Starter motor is likely tired... starts to turn and then stalls,producing the transformer like humming

[Benjisus]

Starter motor is likely tired... starts to turn and then stalls,producing the transformer like humming

Would this require the entire Starter Motor be replaced? And is there a way to test if this truly is the issue before replacing something like that?

[1980GS850]

Would this require the entire Starter Motor be replaced? And is there a way to test if this truly is the issue before replacing something like that?

I had to replace mine last year. your bike has a kick start, does it start with that? Your motor is not tight or stuck right? mine sounded a lot like you describe and found used one cheap on Ebay

[Benjisus]

I had to replace mine last year. your bike has a kick start, does it start with that? Your motor is not tight or stuck right? mine sounded a lot like you describe and found used one cheap on Ebay

I havent gotten the bike to start with the kick start, it seems to turn it over, and if the bike is warmed up I can kick it but to save my leg some pain I havent given it a dedicated attempt from a cold start.
I did check clearances when i was rebuilding my carbs, everything seemed ok but I think im going to open her up and check again today because im seeing this referenced A LOT.

[steve murdoch]

Just like my F150, sometimes a well placed whack with a hammer can jostle a starter into functioning.
The same can apply to your GS. If it works that lets you know it is time for a rebuild.
Stockers kit has worked for me in the past. You just have to determine whether you have a 2 or 4 post starter.

http://www.thegsresources.com/_forum/showthread.php?242129-Bad-starter&highlight=gs750+and+starter+and+rebuild

[Benjisus]

Just like my F150, sometimes a well placed whack with a hammer can jostle a starter into functioning.
The same can apply to your GS. If it works that lets you know it is time for a rebuild.
Stockers kit has worked for me in the past. You just have to determine whether you have a 2 or 4 post starter.
http://www.thegsresources.com/_forum...er+and+rebuild

So based on that forum you linked me to, he tests the voltage of the battery, but ultimately end up saying if you attempt a jump and it doesnt work, its the starter.. So am i pretty safe to assume thats the issue here? Or would it still be beneficial to recharge the battery and test it?

I was able to find this rebuild kit, do you know if this is the kit that would work? I was also able to find this one. (of course once i clarify if its a 2 or 4 post starter)

[Benjisus]

Well I was able to get the Starter Motor off the bike and after soaking a few screws in liquid wrench, finally got the thing open. Like I said, i'm new to the bike world so I really wasn't sure what to expect.. But I don't think what was inside was a good thing.

IMG_20170808_214852.jpg

So its definitely going to need a good cleaning and rebuild, I did confirm that it was this kit I needed to order. Should be here in a few days!

[posplayr]

What does the commutator look like? If it is not flat you can dress it a little with a file.

[Benjisus]

What does the commutator look like? If it is not flat you can dress it a little with a file.

The commutator looked fine, doesnt look like it will need any filing.

[Benjisus]

Hey Everyone,

I got the starter motor rebuilt and that was definitely an issue, however, of course im running into another one. I recently rebuilt the carbs, and now when attempting to start the bike its backfiring everytime it goes to start, would this be a valve adjustment?