Starter Issues '76 KZ750 Twin

Hi All,

I had a starter "rebuilt". After the guy sent me the wrong starter initially, he "assembled" one from a couple including mine. When I hooked it up it will just spin the motor once until I let off the button then sometimes it will spin it over once again. After holding the start button for a while, both battery terminals were warm/hot.

To make sure I wasn't dealing with some other electrical problem, I jumped the starter from the battery direct. Aside from a huge spark, same result. I am thinking the starter is going to ground inside, therefore drawing great amperage. I initially jumped the starter using small-gauge leads and it melted the insulation on the leads.

Battery seems good (correct amperage @ 14A and seems to hold a charge fine). I tried the battery from my kz650 which is 11A with same result.

Thank you,

muddytailgate wrote:

When I hooked it up it will just spin the motor once until I let off the button then sometimes it will spin it over once again.

I am not sure I understand, but if you mean the starter just spins freely, then I would suspect the starter clutch is hosed.

The motor does kick over well I presume? Did you bench test the starter before going to the bother of putting it in??

These big twins are really hard cranking, if it comes to a stop while cranking you want to get off the start button right away. You're just sucking amps and doing nothing by holding the button down, except maybe popping fuses or melting wires.. Releasing and hitting it again is a better alternative. With a weak battery, or bad starter, or poor connections, it's nothing for these to come to a halt on the compression stroke. I know exactly what you're talking about.

That being said, they usually crank fine with a good battery if the starter is working properly, they really don't like weak or cheap batteries.

Make sure the main wire from solenoid to starter isn't frayed or grounding to the engine, if it's close to stock setup still the wire travels along the motor and is held by a couple of plastic coated bendy tabs that can lose their coating and bite into the wire after some vibrating. Make sure feed wire from battery to solenoid is getting a good connection, and make absolutely sure that you're getting a good ground to the engine.

Best to clean the start button with a contact cleaner while you're at it, and insure your getting a good connection there as well.

After checking all that, you should try a simple test. Remove the spark plugs and see how it cranks over, it should just wiz around quickly with no compression. If it does spin freely without plugs in, you could reinstall spark plugs and use a car battery for testing cranking(without car running of course) to see if your batteries are just to weak for the job. It won't be the first time I've seen that. heh

If none of your connections are bad, batteries aren't to weak, starter bench test ok, we'll have to go from there.:blink:

Yes it kicks over fine.

I took the plugs out tonight and jumped the starter direct from battery. With the plugs out, it spins the motor over for a few seconds and then peters out...kind of like a dead battery even though though the battery still tests @ 12V. Is it possible that the battery has lost amp capacity even though it stays at correct voltage?

Tomorrow I will try car battery.

muddytailgate wrote:

...the battery still tests @ 12V. Is it possible that the battery has lost amp capacity even though it stays at correct voltage?....

Yes.
Would charge overnight and have battery load-tested.

Good Fortune!

muddytailgate wrote:

Is it possible that the battery has lost amp capacity even though it stays at correct voltage?
quote]


Yes, the battery can read 12v across the terminals although its load capacity has dropped.....

A battery will read 12v when 100% charged, 60%, 20% etc voltage is irrelevant when cranking amps are involved and what you describe is CCA (cold cranking amps)....... . This is how much charge/"power" the battery can store or has (but don't quote me as I'm not an auto elec, I'm in hydraulics! )

muddytailgate wrote:

Yes it kicks over fine.

I took the plugs out tonight and jumped the starter direct from battery. With the plugs out, it spins the motor over for a few seconds and then peters out...kind of like a dead battery even though though the battery still tests @ 12V. Is it possible that the battery has lost amp capacity even though it stays at correct voltage?

YES. That's exactly what they do when they get old.

Best way to check battery capacity:

Fully charge the battery with trickle charger for a day or two. Put a voltmeter on the battery and then crank the starter. If battery voltage drops below about 9V while the starter cranks, the battery is done and needs replacing.

OK...so charged the battery and the voltage didn't drop much with plugs out. After a bit of cranking, put the plugs back in and cranked it. I would only get one rev or so and the voltage did drop to 9 or 10V. But wait....

Hooked up a good car battery with 700 CCA and aside from almost welding the jumper cable to the starter, maybe I got one or 2 revs.

muddytailgate wrote:

OK...so charged the battery and the voltage didn't drop much with plugs out. After a bit of cranking, put the plugs back in and cranked it. I would only get one rev or so and the voltage did drop to 9 or 10V. But wait....

Hooked up a good car battery with 700 CCA and aside from almost welding the jumper cable to the starter, maybe I got one or 2 revs.

You say it kicks over fine, otherwise I might suspect binding somewhere, or excessive compression.

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So when you've been doing this jumping, you have a ground directly to the motor and then are nailing the starter positive with the other cable end, completely bypassing all the bikes wiring??? Power cable from solenoid is detached also?

If that's the case it would be my opinion that the starter rebuild is simply no good. I'd send it back and get your money back, or leave it sitting there and just kick start the bike.

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If you've been trying to use the ground cable where it normally attaches to the battery as your ground, you've still got some investigating to do.

If you have the power cable from the solenoid attached to the starter while doing this jumping, you might want to try it with the cable removed. Have you inspected that cable from end to end for shorts??

Out of curiosity what is your compression at??

Starter does not sound good. If you are connecting the car battery directly to the starter and it won't crank, it's hosed.

make sure it has a really solid ground as well.

I haven't checked compression, but it seems to kick start with ease...and have turned over by hand before.

When I speak of jumping starter directly, I have securely wired ground from battery to starter bolt (crimp connections at each end of a #10 wire) while holding "+" to terminal on starter, i.e. completely bypassing other electrics.

I think I will have to try and return starter, the problem is he Frankenstein-ed one using parts from mine, so if I send this one back...well I won't have one. Hopefully he will refund my money because I am tired of dealing with this joker.

Thanks for everybodys help, let me know if you guys think of anything else!

Fiore

Just got off the phone with Roger Wallick of motorcycle-recycle-center.com and he says "sorry but I know that starter is good". Bummer.