TOPIC:

Howdy all!

I've got a couple questions on batteries. I've been checking the past posts and haven't quite found the answers I was looking for.

How long should your battery last? I know in cars they are rated by months, but does it work the same for bikes?

Lately I have been having issues with my battery providing enough oomph to start my '78 750. I've checked the voltage across the terminals.

Off 12.97
Idle 1000 rpm 12.85
3000 rpm 14.58

All the numbers seem in line. I can't figure out if I'm loosing charge or I just have a too weak battery. I bought the battery off smithgpz, a member from the old board. It's a sealed Yausa, but I know now they don't make a sealed one for the 750. It's 12Ah instead of 14Ah. Would this make a great difference on cranking power?

I did have to make a new negative battery cable a year or so ago. The old one was hanging on by a couple of strands. Seems tight and making good connection.

Any help will be greatly appreciated!

Thanks!

It's not unheard of for people to have to replace the battery every spring. Normally two years is probably about average, but sometimes you get lucky and might stretch a battery for several seasons.

It also depends on how much you maintain the battery, checking water, keeping it clean, etc.

Obviously the battery cables can affect starting as well as the starter solenoid. To check it, measure the voltage on the two big terminals on the solenoid while it's cranking (it'll take some alligator clips on the meter).

Thanks for the info loudhvx.

I bit the bullet and went to batteries plus and had it tested. The battery read well on all tests until we put it under heavy load. It held for 5 seconds and went down. Gave it a couple of seconds, hit it again...same thing.

I'm still going to check all the connections now.

Thanks!

My battery died on me last summer. It was three years old, and when I took it out to check it, it was DRY. I mean bone dry
I never took it out to check it, just pulled the side panel and looked at it. I thought I was looking at the water level, but it was just a shade line on the battery. So I got a new battery from Autozone, and now I pull the battery about every month (or so) and check the level.

Sixgun, your voltage numbers are just right, so your charging system is doing the job.

I usually kick start my bike when it's cold. It starts well with the kicker, and I think that saves the battery. Maybe it'll last longer that way. Also, I turn off the headlight when I start it. Don't forget to turn it back on!

Glad this topic got hit, because I am having some issues, and don't know where to go with it yet. Even though the battery is two years old, I don't want to buy a battery if it is only going to mask the problem.

Clue was a battery that wouldn't crank the starter.

Started checking things with a multimeter. Battery is 12.2, so it's low, but has never run out of water. I had a kinked vent hose that didn't help things last year, when the gases destroyed my cable ends, but the bike still started and seem to run after all that was sorted out and repaired.

So I pull the sprocket cover as per manual, and on the 200v AC scale, I have 68v at 4000 rpm, which is below the 75v the output is supposed to be at the two yellow dynamo leads. It hits 75v at 5000rpm. The other tests regarding the 6 permanent magnet whizzy thingy seemed to be ok. Do I stop with this, or do I hope that a new battery thrown at the bike will be ok without dealing with this issue first. I suspect that if mine is magnetically decayed over time, I am going to have a hard time finding a good used one.

KaZooCruiser wrote:

So I pull the sprocket cover as per manual, and on the 200v AC scale, I have 68v at 4000 rpm, which is below the 75v the output is supposed to be at the two yellow dynamo leads. It hits 75v at 5000rpm. .

You have two yellow leads? I thought we have three on the 650.

Nope you are right, two leads.

Post edited by: OKC_Kent, at: 2007/03/27 13:38

Part of the problem with my beastie is that the 750 B3 shares much of its starter parts with the 400. The higher compression really puts my battery to work.

I'm with you ltdrider. I usually kick start when the bikes cold. My issue happened earlier this morning when my bike died at a stop light. I tried the electric start...nada....then I kicked it and it decided to be stubborn. I had to pull to the side of the road and give her some attention before she'd start again...

Man I hate that.

working in a shop that specializes in automotive electric. as well as being an avid rider and self proclaimmed bike mechanic for over 30 yrs. let me just say this. Battery's are what they are. Only 1 trick to them. And its called 'TRICKLE CHARGER' The charging system NEVER keeps a battery 'fully' charged. Not in a automobile nor a m/c. The life of any battery is GREATLY increased by keeping it fully charged. Get yourself a good gell battery and a descent self monitoring trickle charger, some come with adaptors that simply attach the your terminals and plug into your charger. You don't even have to raise the seat. I have seen 3 yr. battery's that 5 yrs. later are still in use with no problems utilizing this knowledge. Remember the more often a battery goes dead, or is kept in a weak state the life expectasy is greatly reduced. Remember in the cold winter months to remove it and store it somewhere warm and dry, with the trickle charger on it. Even a WalMart 19.95 battery will last longer under these circumastances. BUT do not cause yourself problems. Get a GOOD battery to start with!

KaZooCruiser wrote:

The other tests regarding the 6 permanent magnet whizzy thingy seemed to be ok.

Show-off, gettin' all technical on us, aren't ya?

OKC_Kent wrote:

KaZooCruiser wrote:

So I pull the sprocket cover as per manual, and on the 200v AC scale, I have 68v at 4000 rpm, which is below the 75v the output is supposed to be at the two yellow dynamo leads. It hits 75v at 5000rpm. .

You have two yellow leads? I thought we have three on the 650.

Nope you are right, two leads.<br><br>Post edited by: OKC_Kent, at: 2007/03/27 13:38

77 had 3 (three phase)
After 77 they went to 2 (single phase)
Then later (early 80's?) they went back to 3.