TOPIC:

After getting stuck in traffic during that heat spell, my battery has barely enough oomph to spin the engine over when it's hot. Stopping for gas and restarting it sounds like an old Ford on a freezing January morning. The battery is only about 1 1/2 yeras old, topped up, connecters clean and tight. Cold starts, it spins the engine just fine. Any ideas?

I generally get a couple years of use out of my batteries in TX where they start the bikes year round. You might have charging issues. Best way to check is to FIRST check the battery. You can take it to a shop where they can load test and that would be best. Otherwise, buy a small hydrometer and test each cell (if it a battery where cells can be tested). In any case, get the SMALLEST hydrometer you can get. It will look like a large eyedropper. Suck in fluid using a small hose and note the number of balls floating for each cell. If any of the cells are less than optimal, some of the balls won't float. The packaging will describe how to interpret.

If the battery appears OK, next look at your regulator/rectifier. This gizmo takes the AC from your alternator and coverts it to DC in the proper voltage. A quick way to check is by using a multimeter. Put the multimeter on the battery and at idle you should have between 12.5 - 13 VDC. Then rev to 4k rpm and check. You should have about 14.5 VDC. Anything over or under that, and your reg/rec is likely toast unless the alternator isn't doing its job of putting enough AC out.

Get a manual to check the AC. On most of the older bikes you should be able to measure AC across any two of the three leads that feed the reg/rec. On the older bikes it this value should be about 20-25 VAC per leg if memory serves. Check your manual for the expected value for your bike and also be aware that your alternator or whatever it is called on your bike may work differently than those I am familiar with.

Anyway, the reason your bike's battery is flopping will show up in one of the tests I outlined. Also, make sure all connections are clean, tight and greased with dielectic grease... any to the reg/rec and battery in particular but also the white/red wire(s) coming out of your reg/rec and going to the 20A fuse and the battery at the solenoid post.

I had a 1982 GPZ1100 that had the exact same symptom and it was a burnt stator. I rode clear from Mobile,AL to NJ and back to Colorado in this condition. Just enough charging to keep the bike running, but not enough for good starts when hot for some odd reason. Mine was charred black physically.

Both suggestions point to the charging system, but I'm not so sure. The battery does charge and does spin and fire the engine when it is cold but after it's been running for a while and has gotten hot, restarting after a short stop it cranks like the battery is almost dead. If I leave it overnight, it spins and fires right up. I've never had to trickle charge it after one of these episodes, it's back up to capacity after the bike cools down.

Fossil wrote:

After getting stuck in traffic during that heat spell, my battery has barely enough oomph to spin the engine over when it's hot....

Perhaps the battery symptom is a red herring? Have you considered that maybe the battery is fine, and it's something else - like the starter or something - that fails when warm?

A good way to test if the battery is really under strain is to watch your headlight when you're hitting the starter, in both normal and the "hot" situations as you described, to see if there's a difference in how it dims. Or, you could use actual tools, like a multimeter, to test. I don't know much about multimeters, but I know a dim headlight when I see one...

I've wondered if it could be the starter, I'll look into that first (or maybe it's just my engine siezing:lol:)

I'm with wg and the checking of the battery. If it only charges to 75% capacity it may have enough juice to start it when cold, but when the tolerances tighten up in the engine it may have more difficulty.

A battery is like a tank of water with a tap. You might have a battery that is reduced in capacity but still flows plenty of current, or the tap might be reduced so you have lots of current available but not a lot of flow (voltage).

Biquetoast wrote:

Perhaps the battery symptom is a red herring? Have you considered that maybe the battery is fine, and it's something else - like the starter or something - that fails when warm?
whistle:

Two friends, two '82 Suzuki 750s, both with "charging" problems. Both replaced all electrical components to no avail. One replaced the starter. One hasn't. One is riding, one isn't.

Not a gearhead, just relaying personal experience.

All the suggestions are good ones. I also had a similar thing on an old 460 Ford engine and it was the ground cable to the engine was cracked and only making about 20% contact.