1982 GPZ750 Starting issues

I'm having a hell of a time figuring out what is going on with my bike. After putting a new Shorai battery in, within a week my starter ceased to work. By that, I mean I was getting a click at the solenoid. I thumbed through the manual and started with the switch. Opening it up, I found that the switch was badly corroded so I replaced it with a newer one. Still clicking, I checked the solenoid itself and did the screwdriver trick of connecting the poles to see if it would click over. Nothing. The battery is fine, I get a healthy 13.1 reading consistently when off and after bumping the bike, it's charging perfectly, 14.5 at 4k rpm. The prior owner had the starter rebuilt in 2014 and it's done roughly 2500 miles since. My starter clutch is beginning to go and has been giving me a little grief lately, but not to the point I thought it would be toast by now.

Any suggestions?

Sounds like either the battery or starter. If you are sure the battery is good then go after the starter. Personally, I'd have the battery load tested before spending the money on a new starter.

Check for bad connections at the battery or ground on the engine. Corrosion at the battery can invisible until you disconnect it.
Steve

+1 on Nessism and SWEST's comments plus one more of my own that fits into what SWEST is poking at. Load testing the battery is to make sure it can source enough current. The electrical potential can be there (voltage) but if it can't sustain sourcing a large current draw the battery could be the bug.
Corroded terminals can create a resistance in the connection like SWEST is referencing. PLUS, if the cable are old and swelled near the terminals, they may be so corroded inside the insulation they are barely conducting electricity. In that case they won't allow enough current flow and will have high resistance as well.

I failed to mention that the negative wire was cleaned and the ground was secured and cleaned about 4 months ago by yours truly. The positive cable was also replaced when I discovered that the connection had been broken over the years. The wires are both in pretty good shape.

I suppose I could have the Shorai load tested. But how do you load test a li-ion bettery?

Fair question and not my area. Does start to make you think about starter and the starter clutch. I've got an 85 GPz 750 and the clutch is crapping out and starting to seize. (my assumption) it has a relatively fresh battery, holds a charge. if you push start the bike and get it hot, the starter works like a dream. I believe something is getting gummy in the starter clutch and when it gets warm it loosens up. But let it set for a week and I've got to push start it. I suppose gummy garbage in the shaft bushings in the starter could cause it to behave in a similar way. I'm not trying to hijack your thread, just relating my experience as it may relate to yours. Once in a while it will turn slowly, then lock, once locked, I get the 'click' and nothing else, just like you describe. I'm planning on pulling the starter and replacing the clutch with my son this winter/early spring.

I just rebuilt my starter on the same bike as yours, 82 GPz 750. I would check the positive cable and ground cables as mentioned by everyone else. Try jumping the battery with another battery see if that helps, or battery charger with start function. If it starts up fine I would consider it to be the battery. If it doesn't do anything, I would pull the starter out bench test with jumper cables, If it doesnt start I would check the brushes in the starter, or check the commutator, see if it its dirty, cleaned mine with emery cloth, thats what the brushes touch on the starter. Rebuilt my starter works much better now. Re-greased planetary gear set with fresh grease.

Well, it's been several months and the problem has worsened. I've ridden the bike a few times since January by bump starting it and it's been fine. On Thursday, I decided to pull the starter to see if there was as visible issue. There was: the brushes were as thick as my thumbnail. I went ahead and used a rebuild kit, reinstalled and attempted to start the bike. Nothing. One click. I turned the ignition off and back on again, pushed the start button and all of the lights went off. All of a sudden, my Shorai battery began to hiss and fizzle and smoke. I let it die down while ventilating the garage and once it was ok to touch, I removed it from the bike. The battery was too hot to touch so I had to cover it with a towel to get it out. Friday, I bought an agm battery from wal-mart on closeout (30 bucks was hard to pass up) to put in the bike in the meantime while I sort out warranty issues with Shorai. I walked through the steps with the new battery friday night and trickle charged it yesterday. After inspecting the fuses and wiring in general, satisfied that nothing had burned up or caused damage otherwise, I installed the new battery and as soon as I touched the positive cable to the positive, I had a massive spark, as if I were touching negative to positive or positive to negative. It was the damndest thing. I again checked the wiring and nothing seemed odd. The workshop manual doesn't really have anything like this in it so I'm not sure where to start or what to do at this point. Is it possible that the polarity has switched?

Any advice is appreciated. The stator will be my first stop this week though, as it turns out, I had it unplugged when this happened. Perhaps the source of the first issue. But I'm going to check it anyway.

What you saw is what it is, a total short. Don't hook the new battery up until you find the short. If you rebuilt the starter I would start there. Your gonna weld something that shouldn't be, or start a fire !

Also if your battery did a fuel Chernobyl it likely fried the harness if not all the fuses anyhwere. Take the starter to get bench tested.

Good luck.

R

rrsmsw9999 wrote: What you saw is what it is, a total short. Don't hook the new battery up until you find the short. If you rebuilt the starter I would start there. Your gonna weld something that shouldn't be, or start a fire !

Also if your battery did a fuel Chernobyl it likely fried the harness if not all the fuses anyhwere. Take the stater to get bench tested.

Good luck.

R

Agree. Sounds scary. There is likely damage as a result of the short. Use your multi meter and trace some circuits to find the source. And I doubt it has anything to do with the stator.

Nessism wrote:

rrsmsw9999 wrote: What you saw is what it is, a total short. Don't hook the new battery up until you find the short. If you rebuilt the starter I would start there. Your gonna weld something that shouldn't be, or start a fire !

Also if your battery did a fuel Chernobyl it likely fried the harness if not all the fuses anyhwere. Take the stater to get bench tested.

Good luck.

R

Once the short happened, or rather once I attempted to connect the new battery, I didn't go back for more, trust me. I've ordered a wiring loom for the bike. I'm going to replace the wiring like I should have when I bought the bike and do it correctly. The starter is fine as all I did was replace the brushes, nothing more. I've got a long weekend of work ahead of me it seems, perhaps more.

Agree. Sounds scary. There is likely damage as a result of the short. Use your multi meter and trace some circuits to find the source. And I doubt it has anything to do with the stator.