1984 ZN1100 weak spark - Kawasaki Motorcycle Forums
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post #1 of 12 (permalink) Old 01-06-2017, 01:01 PM Thread Starter
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1984 ZN1100 weak spark

Hello. I am new to this site and would like to know if anyone can help me with my bike. I have a 1984 ZN1100 LTD that I bought as a re-builder. It runs very strong but after I ride for about an hour it starts to load up and loose power at a steady throttle. When I give it gas it will run strong but stumble on acceleration. It will idle fine at a stop light. MPG is horrible and when I look at the spark plugs they are black. I have rebuilt and synced the carbs and replaced the ignition coils. Any advice would be greatly appreciated. Thanks.
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post #2 of 12 (permalink) Old 01-06-2017, 01:15 PM
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1. Charge your battery using a low amp trickle charger overnight. With key off, measure voltage. If the battery is in poor condition, it will measure less than 12.5VDC. Should be around 12.9VDC after charging or more. If battery tests OK:

2. Start bike and run it at 4K rpm. You should see about 14VDC or a shade more. If you see less, your stator may be on its way out or your regulator/rectifier may be shot. If your battery isn't charging sufficiently, the stator or reg/rec may be bad. If you see more than 15VDC at 4K rpm, the reg/rec is definitely bad.

3. Read and do the things suggested in this article:
Repowering Ignition Coils

4. Get your manual out and see if there is a way to check the IC Igniter.

5. Your wiring harness may have poor connections and should be gone through in any case to ensure everything is OK. Take a look at your fuse box and make sure nothing looks toasty there. I always just replace the stock fuse box anyway with a modern blade-type box.

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post #3 of 12 (permalink) Old 01-07-2017, 10:11 AM
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How old is the battery & what type is it? If it's a wet cell, make sure the electrolyte level is correct in each cell. If low, add distilled water. An AGM battery would be good to have or to get. I'd guess any AGM would be good. Yuasa batteries are made in USA. Before buying my last battery, I didn't think to check into those. doh.

High beam load test (engine off). charge the battery with a good motorcycle smart charger. It should be at least 12.6 VDC, but a good battery will be higher. Turn on the ignition switch, high beam ON (engine off). A good battery will drop to about 12.2 VDC. If it drops a little below 12 VDC, the battery may need replacing, but it may be okay. If it drops below 11 VDC, the battery is probably shot.

I have a Scorpion AGM from batterystuff.com. It was 12.79 VDC straight out of the box & it has been a good battery. and I use a Ctek US 0.8 smart charger & VC97 digital multimeter.

1981 KZ650-CSR. Competition, Sports & Road.
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post #4 of 12 (permalink) Old 01-10-2017, 10:23 AM Thread Starter
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The battery is brand new but I haven't did a load test on it. Is there a chance that the stator is making this happen?
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post #5 of 12 (permalink) Old 01-10-2017, 05:46 PM
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What type of battery is it & was it properly serviced before installing it on the motorcycle.

If the voltage regulator or stator are defective, the battery may not be charging properly.
First step, though, is to make certain the problem isn't the battery.
Many a rider has made the assumption that it's not the battery, but you never know until you test it.
My last wet cell battery didn't hold a charge very good from the get-go. So I got a Scorpion AGM.



....

1981 KZ650-CSR. Competition, Sports & Road.
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post #6 of 12 (permalink) Old 01-12-2017, 09:47 AM Thread Starter
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The battery is an Xtreme AGM from batteries plus. I put it on my Battery Tender until it was fully charged and have had it on the battery when ever I'm not riding. It seems to have plenty of cranking power even after I've been riding for a while so I'm thinking that it's being charged. I will do a test on the stator and voltage regulator as soon as I can.
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post #7 of 12 (permalink) Old 01-12-2017, 11:03 AM
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These old bikes tend to have corroded electircal connections. Go back and read post #2. Cleaning all of the electrical connections just might fixer.

1985 Kawasaki ZN700 Shaft, 4cyl
1989 Yamaha Venture Royale
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post #8 of 12 (permalink) Old 01-12-2017, 11:28 AM Thread Starter
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Thanks Roadrunner322, I will do that. Thank you too martin-csr.
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post #9 of 12 (permalink) Old 01-13-2017, 08:18 AM
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Are the spark plugs sooty black or oily? Sooty black could be ignition related from poor spark.

Redo the spark plug wire connections at all points. Doing so solved an intermittent firing problem on my 650. Unscrew the ribbed compression boots at the coils to disconnect the plug wires there. If the wire is dull from oxidation, nip off the ends a tad. Or go ahead & install new spark plug wires. Also, clean up the igniter leads on the cols. simply disconnecting & reconnecting helps.

Coils. A simple test is to ride the bike at highway speeds, then stop & feel the coils. press hard with your fingers. they should be warm, not hot. my neighbor has the same bike as mine & his coils would only get warm, while mine were getting very hot to the touch. So I got a pair of green Dyna coils & spark plug wire set from Z1Enterprises.com. The new coils solved a high speed miss & running problem. I think the grey 2.2 ohm are a better match for the stock ignition system, but the green ones are okay to use.

Fuel related. Also, make sure the tank is venting & the petcock is working right. you never know sometimes.

1981 KZ650-CSR. Competition, Sports & Road.

Last edited by martin-csr; 01-13-2017 at 08:26 AM.
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post #10 of 12 (permalink) Old 01-16-2017, 09:14 AM Thread Starter
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The plugs are sooty but I've replaced the coils and spark plug caps. The caps are resistor but the plugs are not. The fuel system was the first thing I worked on and everything is in working order.
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