T500 - No/Weak Spark at Left Cylinder

All to do with wiring, charging or just trying to figure out whats gone wrong.

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DaytonDave
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Suzuki 2-Strokes: 1968 T500
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Re: T500 - No/Weak Spark at Left Cylinder

Post by DaytonDave »

karl pa,
Thanks for the information on your experience with this issue. Seems that updating the electronics is what is needed.
Not sure what you meant by charging coils? Are you referring to the alternator windings?
Thanks
Dave
karl pa
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Re: T500 - No/Weak Spark at Left Cylinder

Post by karl pa »

The GT500 has a different charging system than the T500, but yes the charging coils are more or less the alternator winding.
Upgrading the system depends on your intended use. If you intend on riding the bike, I would recommend doing, the parts are concealed so it doesn't take away from originality, but gives reliability.
The nice thing with Rex unit, it looks like it is plug and play, no cutting and splicing wires.
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jabcb
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Re: T500 - No/Weak Spark at Left Cylinder

Post by jabcb »

What is the history of your T500? Have you owned it for a while & it used to run fine? Or is this a recent purchase & you’ve never had it operating fine?
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
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jabcb
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Re: T500 - No/Weak Spark at Left Cylinder

Post by jabcb »

Additional upsides of upgrading to a modern rectifier/regulator: (1) they are more efficient than the stock rectifier so you’ll get more output from your alternator, and (2) they are much better at controlling voltage so your lights will last longer & you can upgrade to a modern AGM/sealed battery.

This is how I mounted a Tympanium rectifier/regulator on a T500.
viewtopic.php?f=2&t=8260&p=129033
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
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DaytonDave
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Posts: 18
Joined: Fri Jun 03, 2022 1:37 pm
Country: USA
Suzuki 2-Strokes: 1968 T500
Location: Dayton, Maryland

Re: T500 - No/Weak Spark at Left Cylinder

Post by DaytonDave »

jabcb and karl pa,
Thanks for the advice. I ordered Rex's unit yesterday and looking forward to having a reliable and modern electronic charging system.

jabcb, as you asked, the history of my bike is that I ordered it new in 1968 from the dealer who was a friend. When it arrived, I opened the crate and assembled it myself completely (at age 19 then). A few weeks later, I rode it across the USA. I rode it for many years after and it was always super reliable. I then stored it indoors for many years. Just recently, I decided to go through it and get it running again and plan to be riding it again. It has 11,3XX original miles and has been a one owner bike all these years and is 100% original except for the tires. It is actually one of the rare early "500/FIVE" versions of the T500's with the slightly shorter wheelbase and the larger Mikunis.

This forum is great and I am really enjoying the input and support from everyone. The bike and I are kind of old together, lol.

My other bike is a 2004 Gold Wing, but this Suzuki has been with me for for 54 years! :wink:

Dave
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jabcb
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Re: T500 - No/Weak Spark at Left Cylinder

Post by jabcb »

The T500 alternator has charging & lighting coils. The lighting coil is controlled by the switch that turns on the lights — the lighting coil generates output only when the lights are on.
The stock wiring is here. Your early T500 will be a little different because the ignition switch also operates the lights.
https://ozebook.com/compendium/t500_files/t500wire.jpg

I modified the wiring a bit when using a modern rectifier/regulator so that the lighting coil is always active. See:
viewtopic.php?f=2&t=4858&p=109480&hilit ... um#p109480
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
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DaytonDave
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Suzuki 2-Strokes: 1968 T500
Location: Dayton, Maryland

Re: T500 - No/Weak Spark at Left Cylinder

Post by DaytonDave »

jabcb,
That's a very nice and neat wiring job and installation.
The improvements cited by many here have emboldened me to upgrade as well.
At this point, I have an order into Rex's for a reg/rect module and two (2) new HT coils. The order was processed today and I hope to be able to install it in about a week. I will provide an update on the results when installed. Kinda anxious now to get it done and hoping for good results. I had bought two used coils off EBay but both failed secondary testing. Decided it was time to get some quality replacement new coils. I compared Rex's custom made unit specs with some other less expensive ones and they sound good. Will find out pretty soon.
DaytonDave :wink:
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DaytonDave
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Posts: 18
Joined: Fri Jun 03, 2022 1:37 pm
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Suzuki 2-Strokes: 1968 T500
Location: Dayton, Maryland

Re: T500 - No/Weak Spark at Left Cylinder

Post by DaytonDave »

This is a follow up to my journey through the left cylinder firing intermittently or not at all. Thanks for all the suggestions.

Success! Based on the advice from several here, I replaced both coils and upgraded to a modern solid state rectifier/regulator combination - all from Rex's Speed Shop. The result is that both cylinders now have excellent bright spark and it's running on both cylinders. 8)

Took the bike for a short trial run and acceleration was as awesome as I remember from decades ago when it last ran. I put some Seafoam in the fuel to help clean the fuel system, even though I had rebuilt the carbs.

Thanks again to the folks who contributed to this thread. :up:

DaytonDave
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