How do YOU jump start an old GS?

[OriginalOwner]

1981 GS750EX:

Taking it out of winter mothballs today, battery was stored indoors, and is "good" reading 12.6 volts on the multi-meter -- but it's just not enough to crank this hard-to-crank old beast for more than 1 or 2 seconds.

This is quite typical and what I usually do is give a push down my hill and jump on, pop the clutch in 2nd gear and she'll usually start right up. But right now, I can't because i'm injured.

So, how does one get some cranking amps to this battery to get it started?

GS750side2.jpg

[pdqford]

Put it on a trickle charger for a few days?

[Rich82GS750TZ]

At least it’s nice to look at sitting there doing nothing. If you are indeed the OriginalOwner you’ve done a superb job of preserving this bike.

Time to get out the volt meter. Put it on the battery and tell us what voltage you have at:

key on:
key on while pressing the start button:

My guess is the second reading will be in the 10-11v range, not enough juice to satisfy the needs of the starter motor.

This should tell us whether the battery is “good” or not.

If you still have 12v or more while pressing the start button, your starter motor could need some attention/clean/brushes.

Getting ahead of myself but once it’s running you could report all 6 voltage readings seen in the Quick Test link in my signature to check the health of your charging system.

[RichDesmond]

Battery Tender or similar will have the battery up to snuff in at most a day or so. Wal-mart or an auto parts store will have something if a bike shop isn't nearby.

[OriginalOwner]

Mr. Original, you've been around nearly 3 yrs. Is there a reason this bike hasn't been in the BOTM section?, or did I just miss it?,

i've been here way longer than 3 years. A few times, I'd just be stalking for extended periods and they'd cancel my account for not signing in. I didn't even realize I wasn't signed in - so I'd have to make a new account. I think they quit doing that.

My opinion, Pull the left side cover, find the large pos. cable that connects to the batt. (be sure not side going to starter) and connect pos. batt. charger lead to it. connect neg. batt. charger to any known ground, probably top shock mounting nut.... Next time replacing batt. put short jump wire, with female connector, from pos. batt post out to behind side cover. Will be handy to do what you're doing now, also to connect trickle charger. Dang it's a pain to get to the batteries on those bikes.

I installed leads for the trickle charger under the left-side, side cover. I fear any robust amperage would likely melt those cables.

Battery Tender or similar will have the battery up to snuff in at most a day or so. Wal-mart or an auto parts store will have something if a bike shop isn't nearby.

I have like 20 different all types of battery chargers - I haven't tried every single one but the better ones say the battery is good and stop charging it. And we all know how easy it is to fry a motorcycle battery with a crappy charger that doesn't shut itself off - even 2 amps can cook 'em good.

[OriginalOwner]

At least it’s nice to look at sitting there doing nothing. If you are indeed the OriginalOwner you’ve done a superb job of preserving this bike.

Time to get out the volt meter. Put it on the battery and tell us what voltage you have at:

key on:
key on while pressing the start button:

My guess is the second reading will be in the 10-11v range, not enough juice to satisfy the needs of the starter motor.

This should tell us whether the battery is “good” or not.

If you still have 12v or more while pressing the start button, your starter motor could need some attention/clean/brushes.

Getting ahead of myself but once it’s running you could report all 6 voltage readings seen in the Quick Test link in my signature to check the health of your charging system.

I'll do all this but I'm more inclined to believe that my starter motor is the problem and probably has been all along. All these years and I didn't even know this was even a thing?

Can you point me in the direction of a "how to" or just a guide for what is entailed with reconning my starter motor?

Thanks!!

[Rich82GS750TZ]

Could be a link to something on BikeCliffs Website. I don’t recall. Or some threads here on this site. You could try a search. Link to that site first in my Signature. Bookmark it and reference it often.

We have the same engine. IIRC, it was necessary to remove the carbs in order to remove the cam chain tensioner in order to remove the starter motor. The two bolts that hold down the rear of the starter are real knuckle busters to get out otherwise, if it’s even possible. I would check your voltages first. No need to remover the starter yet if you find that you’re not getting enough voltage to the starter when you press the button.

Years ago, I removed my starter motor when it started behaving feebly, I took it out, took it apart. Saw that the brushes needed replaced and was kinda grungy generally. My town has a terrific small electric motor shop. I let them refurb and test it for me. Don’t recall the price but it was cheaper than my time.

[chuck hahn]

From a car that IS NOT running. You can short across the selinoid terminals with a screwdriver to see if the motor turns if it wont crank with the button. To tell iff tgere is eveb a reaction from the button unplug the wire lead going to the selinoid and put the red probe from the meter into the female side on the harness and see if theres voltage when pressing the button.
If you have voltage when you press the button and it cranks when shorting the terminals but not when using the button id surmise the selinoids toast

[Rob S.]

Get a new battery.

[OriginalOwner]

Sorry, I read more into your question than you were asking. If your starter "button" cranks for a couple of sec., your starter circuit should be working. Connecting to the batt. cable, at the solenoid, is the same as connecting to it at the batt. Kind'f hard getting cable clamp to that little 10mm nut (post) without touching something else. A small pair of vice-grips makes it easier to connect to that little nut, then ground to shock nut.

Great idea! I can actually go to both posts with small vice-grips and use a higher amperage charger - even have one with a "start" mode.

The air box won't be in place but i can figure out some sort of cover over the open throat to simulate the same restriction. I have done that before, not sure why or when but I know it can be done.

[Suzukian]

double post sorry

[Suzukian]

Jumping it from a car battery is something you can do on these older bikes. I keep a car battery fully charged, on the floor, just for that reason. On some of the really modern ones, they may burn on some components that have CMOS or other extremely low voltage chips, that aren't well protected can burn out. On a well designed system this shouldn't happen, but one slip and spark can blow out a lot on a New bike. You should be god to bee. Put the bike on the center stand though. The vice grips to get a good connection is a great idea.

Problem with battery chargers is they don't measure the specific gravity. You may get a surface charge or 12 volts or more, but there is no current behind it. Get a Specific Battery tester to check each sell to find out if the battery is any good. You can still ump the bike with the battery you have. Even if it's low, as long as the battery you connect in parallel is up to the job.



Specific Gravity Tester.jpg

[rphillips]

I thought you were having trouble getting to batt. posts due to air box, I guess not if air box is out. All I can say, like anything else, pos. to pos. and neg. to neg. and personally, I wouldn't use start mode of charger on a bike. but that's just me. Good luck. and your bike should be in BOTM.

[Suzukian]

I have to agree with rphillips on that. You are better off using a battery. Also, you bike is super clean!

[tom203]

Get a new battery…a few years back at season startup, my well charged battery looked great on meter, but failed to excite starter motor…..new battery brought it to life instantly..
very nice looking bike!