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PostPosted: Tue Aug 28, 2018 12:47 pm 
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Around the block

Joined: Wed Aug 22, 2018 10:55 pm
Posts: 80
Country: USA
Bikes owned: GT100, GT500
Hi experts,

Suzuki GT500:

Facing a strange/perplexing connection problem between Spark Plug Connector and the black thick wire that comes out of
ignition coil.

When I thread in the spark plug connector into the ignition coil wire, the connection gets LOST.
I dont understand what is causing it, and how to fix this.
Anybody faced similar issue? How did you fix this?

PS: it happens only to the right side spark plug, left side connection is fine.

Thanks in advance.


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PostPosted: Tue Aug 28, 2018 12:57 pm 
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Novice racer

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 955
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
GT500-2stroke wrote:
Facing a strange/perplexing connection problem between Spark Plug Connector and the black thick wire that comes out of
ignition coil.

When I thread in the spark plug connector into the ignition coil wire, the connection gets LOST.
I dont understand what is causing it, and how to fix this.
Anybody faced similar issue? How did you fix this?

PS: it happens only to the right side spark plug, left side connection is fine.

Thanks in advance.

I am guessing you mean that the spark stops if you add the plug cap?
I would initially suspect the plug cap is faulty. Check this first (try swapping with left one to see if problem persists or not).
However if your points circuit has a high resistance you could be getting insufficient oomph to pass through the resistor in the cap.
Check condition of points and dwell angle. Make sure you have no resistance in the low tension circuit to the right coil. Check input voltage is the same on both coils.
That should help you find the culprit. It is also vaguely possible you have a coil problem, but that is less likely than a wiring fault or points badly pitted etc. If the points are badly pitted replace them AND the condensors.
Good luck


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PostPosted: Tue Aug 28, 2018 1:54 pm 
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To the on ramp

Joined: Tue Mar 10, 2015 12:35 pm
Posts: 478
Location: Wales
Country: WALES
Bikes owned: suzuki gt 550j
Try this. Remove the plugcap. Cut a few mm off the end of the thick black wire(high tension or HT lead)then screw the plug cap back in see if that works.

_________________
98 carb Blackbird and GT550j


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PostPosted: Tue Aug 28, 2018 2:24 pm 
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On the main road

Joined: Sat Sep 05, 2015 3:14 pm
Posts: 175
Location: southeast pa
Country: us
Bikes owned: GT
The GT500 uses PEI , it does not have points, it uses the same ignition coil to fire both plugs at the same time, one piston is up the other is down, if you have spark on one plug I would think it is plug cap or plug wire issue.
The GT500 PEI has a weak point, the low speed coil fails, which gives a weak spark when trying to start, but this is both plugs not just one.

_________________
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe


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PostPosted: Wed Aug 29, 2018 6:38 am 
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Around the block

Joined: Wed Aug 22, 2018 10:55 pm
Posts: 80
Country: USA
Bikes owned: GT100, GT500
sportston wrote:
GT500-2stroke wrote:
Facing a strange/perplexing connection problem between Spark Plug Connector and the black thick wire that comes out of
ignition coil.

When I thread in the spark plug connector into the ignition coil wire, the connection gets LOST.
I dont understand what is causing it, and how to fix this.
Anybody faced similar issue? How did you fix this?

PS: it happens only to the right side spark plug, left side connection is fine.

Thanks in advance.

I am guessing you mean that the spark stops if you add the plug cap?
I would initially suspect the plug cap is faulty. Check this first (try swapping with left one to see if problem persists or not).
However if your points circuit has a high resistance you could be getting insufficient oomph to pass through the resistor in the cap.
Check condition of points and dwell angle. Make sure you have no resistance in the low tension circuit to the right coil. Check input voltage is the same on both coils.
That should help you find the culprit. It is also vaguely possible you have a coil problem, but that is less likely than a wiring fault or points badly pitted etc. If the points are badly pitted replace them AND the condensors.
Good luck


Sorry I was not clear.
Actually I do not have spark in either spark plug yet.

I am trying to find out why there is no spark.

In other words, I am currently in the process of finding out why there is no spark, using multimeter.

I am using multimeter to check ignition coil and connectivity between output of coil and end of spark plug cap.

1. When I removed both spark plug caps and attached multimeter between two ends of ignition coil: Multimeter reading is ~17.5 KOhm

2. When I re-attach spark plug caps and attach multimeter at the end of spark plug caps: Reading is infinite Ohm ( open circuit)

3. When I attach meter to both ends of spark plug caps: Reading is ~7KOhm.

Thanks.


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PostPosted: Wed Aug 29, 2018 6:45 am 
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Around the block

Joined: Wed Aug 22, 2018 10:55 pm
Posts: 80
Country: USA
Bikes owned: GT100, GT500
GTandcbr wrote:
Try this. Remove the plugcap. Cut a few mm off the end of the thick black wire(high tension or HT lead)then screw the plug cap back in see if that works.


Will try and see how it goes..

I was also thinking of cutting spark plug cap a little bit to expose the threaded part, and then solder a thick wire to the threads.
Then solder other end of wire to the thick black wire ( HT lead ).
This is if above still does not work.

Where do I buy a replacement spark plug cap ? as I prefer not to cut original spark plug cap.
Will I find it at any auto parts store ?

Thanks.


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PostPosted: Wed Aug 29, 2018 7:36 am 
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Moto GP
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 3381
Location: southwestern Pennsylvania
Country: USA
Bikes owned: 69 T350 thru 75 GT750
There are resistors in the plug caps. A bad resistor can give you the open circuit reading you got.

You can still get plug caps from Suzuki if you want but they want silly money for them.

Most people get NGK plug caps. You have a choice between resistor plug caps + non-resistor spark plugs, or non-resistor plug caps + resistor spark plugs.

_________________
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 73 project
T350 69, 71 & 72 project
T250 72
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE


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PostPosted: Wed Aug 29, 2018 10:09 am 
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To the on ramp

Joined: Tue Mar 10, 2015 12:35 pm
Posts: 478
Location: Wales
Country: WALES
Bikes owned: suzuki gt 550j
If you have no sparks at all dont waste time with plug caps. Start by checking the three coils on the magneto first. Also you cant start cutting and soldering High Tension leads you will lose continuity.
Another link for you
https://www.oldjapanesebikes.com/mraxl_ ... s/page-A59

_________________
98 carb Blackbird and GT550j


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PostPosted: Wed Aug 29, 2018 2:27 pm 
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Novice racer

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 955
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
GTandcbr wrote:
If you have no sparks at all dont waste time with plug caps. Start by checking the three coils on the magneto first. Also you cant start cutting and soldering High Tension leads you will lose continuity.
Another link for you
https://www.oldjapanesebikes.com/mraxl_ ... s/page-A59" onclick="window.open(this.href);return false;

+1 on that.
Fiddling with plug leads can often lead to electricity sparking to earth prematurely, either through the bike or YOU. 50,000volts could kill you if you have a weak heart, or at least give you an unpleasant shock. Either way it is annoying.
I revise my earlier suggestion, I was unaware that the GT500 had electronic ignition, whilst the T500 didn't; So forget checking points. Instead check the low tension side of the EI.
Check you have 12v + at the coils.
Check the output from the EI unit and check that it is getting to the coils.
Check the input to the EI unit.


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PostPosted: Wed Aug 29, 2018 3:44 pm 
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On the main road

Joined: Sat Sep 05, 2015 3:14 pm
Posts: 175
Location: southeast pa
Country: us
Bikes owned: GT
You should start by checking wires coming from magneto, check resistance between gr and b/w wires, this is the low speed coil it should have around 185 ohms, then b/r to b/w wires, this is low speed and high speed coils in series it should be around 214 ohms.
What I found on mine when the low speed coil drops to around 120 ohms it will not give enough spark to start.Just last week it gave me trouble, I had 0 ohms between gr and b/w, turned out to be a broken wire.
If you look at service bulletin GT-28, it shows the resistance values of the coils.
sportston wrote:
Check you have 12v + at the coils.

On the GT500 PEI, it is not tied to the battery system at all, so you will not have 12 volts anywhere in the system. I am not sure what the voltage is to be going to the coil, but it is generated from the magneto.

_________________
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe


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PostPosted: Thu Aug 30, 2018 1:48 pm 
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Novice racer

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 955
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
karl pa wrote:
sportston wrote:
Check you have 12v + at the coils.

On the GT500 PEI, it is not tied to the battery system at all, so you will not have 12 volts anywhere in the system. I am not sure what the voltage is to be going to the coil, but it is generated from the magneto.

I stand corrected. I can see from the workshop manual it is an unusual ignition system, relying upon the positive side of the coil being switched. Thanks for pointing out my error. As ex car technician, my mind usually reverts to thinking of car based systems of which nearly all are negatively switched, as are those of my own Suzukis.
This page may be of some use to you in understanding the system.
https://www.oldjapanesebikes.com/mraxl_GT_Resource/manuals/t500_service/index.php
Click on GT500A Electrical section for info on the PEI system. It has a nice diagram of the system


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PostPosted: Thu Aug 30, 2018 3:17 pm 
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On the main road

Joined: Sat Sep 05, 2015 3:14 pm
Posts: 175
Location: southeast pa
Country: us
Bikes owned: GT
sportston wrote:
it is an unusual ignition system


That is a polite way of describing it, I would have a few harsher words to describe it :evil: over the years I spent way to many hours troubleshooting and repairing this ignition and charging system, give me points any day.

_________________
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe


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PostPosted: Fri Aug 31, 2018 7:13 am 
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Around the block

Joined: Wed Aug 22, 2018 10:55 pm
Posts: 80
Country: USA
Bikes owned: GT100, GT500
Just want to thank you all for helping me get to the point of finally getting spark! :up:

( I am still working on replacing HT leads etc..but
all of you helped and I am grateful for all the tips and suggestions. )

:up:


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PostPosted: Sat Sep 01, 2018 12:57 pm 
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Novice racer

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 955
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
Excellent. Well done. :up: What was the cause of the problem?


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