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Discussion Starter · #1 ·
HI,

my 1984 GPz1100 A2 runs poor around 2000 to 2500 rpm. The engine abruptly stop running for a brief period and a tachometer jumps up. It doesn't happen when the engine runs without a regulator rectifier. The engine runs fine without a regulator rectifier. Have anyone experienced same or similar and what would be the cause?

I checked the regulator rectifier with multi meter following the service manual. It seems fine.
When I removed the regulator rectifier from GPz, I found one of yellow and ground (black) were burned at the connector. I replaced regulator rectifier and main harness couplers to undamaged one from my stock.
I checked ground wiring to see if there is brake / cut using multimeter. It didn't detect any resister or brake.

My GPz runs with stock DFI.
I am using a YUASA YTX20L-BS battery. I start suspecting the stock regulator rectifier doesn't work well with it.

Thank you!
 

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You should also follow the wires from the alternator all the way to your regulator. I suspect you will find melted wires/connectors along the way.
Alternator connections on my 1985 Concours were literally charred along with the wiring a few inches towards the alternator. I replaced the connection with a two lead trailer plug kit and it works fantastic, fully waterproof and no signs of overheating.
 

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Only two leads? Or are you using the ground as the third lead?

Charred, melted alternator wires and connectors are a very common problem on vintage bikes. It is one of the first things that should be checked. You have to remove a few covers but well worth the investment in time.
 

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Only two leads? Or are you using the ground as the third lead?

Charred, melted alternator wires and connectors are a very common problem on vintage bikes. It is one of the first things that should be checked. You have to remove a few covers but well worth the investment in time.
Yes, these only have two leads. Pic of OEM from eBay
Cuisine Gas Automotive lighting Drink Metal
 

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Discussion Starter · #8 ·
I'm sorry, it's been two months since I posted. I have an up-date finally....
I renewed all bullet connectors from alternator and main harness. I cleaned (polished) all six of blades in a connector connect to a Regulator/Rectifier. I used new a Regulator/Rectifier which from my stock.
Result was same...
 

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If you're up for some data gather for troubleshooting, I suggest:

test 1: Voltmeter across the battery, readings at idle and 2500 rpm, with everything connected.
then
test 2: Voltmeter across the battery, readings at idle and 2500 rpm, with regulator/rectifier . DISCONNECTED

I'm not convinced that it's an electrical problem; can you provide some background info, mileage, maintenance, last time it ran okay, etc.?
 

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Discussion Starter · #10 ·
So, do I read voltage from the battery + and - terminal with battery and the r/r connected?

I bought it in 1994. It is 43,000 miles if I trust odo. Ex and in valves, guides and seats were refreshed 11 years ago. Routinely oil and filters are changed and air cleaner is cleaned.
The issue appeared about 5 years ago once in a while and it wasn't as sever as now. It doesn't happen when the r/r are disconnected.
 

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Discussion Starter · #12 ·
I see.
I did it although I read voltage at tach (You know, you can read voltage with holding the push button next to tach.

With reg/rect disconnected,12+ at idle and slightly goes down at 2000 rpm.
With all connected, 13+ at idle and 14+ at 2000 rpm then voltage jump up when it happens.

I should read voltage with voltmeter as you instructed, shouldn't I?
 

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I'll post the same thing again, make a harness going from the Stator directly to the R/R, then from the R/R/ directly to the battery. do not use any of the stock wiring. If you haven't done this, you are not isolating the problem. :)
 

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Discussion Starter · #14 ·
I'll post the same thing again, make a harness going from the Stator directly to the R/R, then from the R/R/ directly to the battery. do not use any of the stock wiring. If you haven't done this, you are not isolating the problem. :)
The white/ red from the R/R to the battery positive and the black to the battery ground? How about the brown?
 

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I must admit to confusion here, I've never disconnected a reg/rect to make a bike run better and I don't yet understand how it would affect performance.

I did note the following:

"I suspect you will find melted wires" especially the black/yellow wire, it's the harness ground wire and I can't remember
a time when it was burnt in only 1 place. Recommend open entire wire harness and track every black/yellow wire.

"runs poor around 2000 to 2500 rpm. The engine abruptly stop running"
Could be 2 different problems? "runs poorly" may be carburetion. "abruptly stop running" is usually a loose
or poor connection at a plug or in the switch or at the battery or at the wire harness ground wires.

"using a YUASA YTX20L-BS battery"
That maybe too much battery for this particular bike; maybe that caused the burnt wire problem?

"make a harness going from the Stator directly to the R/R, then from the R/R/ directly to the battery."
I agree, even though I don't yet understand why we're chasing electrical, not carburetion?
 

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Discussion Starter · #16 ·
Sorry for giving you confusion.
"The engine abruptly stop running" is more accurate. It is like the switch goes on, off, on, ,,,,off, on,, off, on, off, on,,,, .
Disconnecting a reg/rect doesn't make a bike run better. It makes a bike run normal.

It is dfi. Not a carbureted.

I have a feeling about the battery, too. Maybe the R/R doesn't like it... ? The R/R becomes hot which understandable although I don't know how hot is normal. Its connector become hot, too.
 

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"It is like the switch goes on, off, on, ,,,,off, on,, off, on, off, on,,,, ."
Sounds like a relay clicking on, off, on, off.

If you can get it to go on, off while on the stand, then touch every relay or switch, see if you can feel the click on, off, on...

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Just as an FYI, using the tach button to read voltage is not accurate. It can be off by a volt or two. Mine was indicating barely above 12 volts, when in reality the battery was being charged at a little over 14 volts.

So yes, you should get yourself a good multimeter and measure at the battery.
 

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Yes you should use a good quality meter, but you are using the same meter for your tests. It is indicating that your bike is running on the battery only with the regulator disconnected. (12V) It will run fine like that until the battery gets low enough that stuff stops working. With the regulator connected the voltages look like they are doing what they are suppose to until the voltage rise gets to where the voltage is supposed to be regulated.(13v TO 14v) At that point the voltage spikes up and the bike misses. What voltage? At this point is it beyond the range of the onboard meter?

What happens when you take the rpm above the point where it misses. Does the voltage come back down to a correct regulated voltage or does it stay high? Does the bike run correctly at a higher RPM?

With the bike being DFI I am guessing, just guessing that something in the DFI doesn't like that voltage spike and is trying to protect its self. I also don't know enough about how the regulator works or DFI to help with what is causing it.
 

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Discussion Starter · #20 ·
I checked the voltage with multimeter now.
Battery itself is 12.54.
12.03 w/o R/R at idle
12.65 w R/R at idle
12.50 w R/R at 2500 or 4000rpm.
When it happens, the voltage changes +/- 0.1 at 2500rpm. The onboard meter moves just slightly around 13.8.

The engine doesn't run smoothly with R/R when rpm is higher (3000, 4000.

Here is the voltage on the alternator.
25 at idle, 41 at 2500 and 65 at 4000. The service manual says 50 at 4000. So, 65 is high. I, don't know if it is in the range...
 
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