Intermittent and lack of spark.

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Norton nut
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Suzuki 2-Strokes: 1970 tc90

Intermittent and lack of spark.

Post by Norton nut »

I'm not getting any spark when I check by holding the plug and grounding it to the cylinder head. The bike was running but then started to die once I started to go up through the gears. I'd start it up, get rolling then it would die. Figured I'd check plug and now there's no spark and no start. I did check to make sure the points are opening, which they are at TDC. Could the ign-coil be hooped? Any suggestions or thoughts?
GT750Battleship
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Re: Intermittent and lack of spark.

Post by GT750Battleship »

:shock: Hi,totally dead battery,or the points have closed up..check everything is getting power...ignition,points,lights,could have just blown a fuse,let us know what you find !!The coils hardly ever play up by the way 8)
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Norton nut
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Suzuki 2-Strokes: 1970 tc90

Re: Intermittent and lack of spark.

Post by Norton nut »

Thanks for the response, battleship. The points are opening, gonna advance it a pinch. I'm suspecting a frayed wire or such. Or a bum ign-coil. Looking for my puller and will take a good look inside the rotor. Will let you all know once I get a spark.
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Alan H
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Re: Intermittent and lack of spark.

Post by Alan H »

Does the neutral light dim when you switch the kill switch on? If it doesn't then there's a problem either to the coils or between coils and points. Check the multiplugs under the side panel areas and near the coils.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
Norton nut
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Suzuki 2-Strokes: 1970 tc90

Re: Intermittent and lack of spark.

Post by Norton nut »

Thanks for you guy's input. This is a '70 tc 90 it doesn't need to be turned on (with a key, don't have one anyway) in order to generate a spark via the rotor to the ign-coil to the plug. It had a spark and was running earlier. Problem is it dies. When I ground the plug to the cyl-head there is no spark now. I've reset the points gap (just approximately, anyone know the exact gap spec.?), checked the points wiring for frays or breaks, cut back the coil lead and insured the plug cap is well connected and still no spark! I'm not quite at the "hair pulling stage" but I might have to go kick the dog ;)
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Alan H
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Re: Intermittent and lack of spark.

Post by Alan H »

Ahh, sorry. For some reason I thought you were referring to a triple!
Dunno where that came from - maybe an alcoholic haze!
Normal points gap is about 15 thou but if you've had the points apart, make sure the insulating washer(s) are fitted correctly otherwise the points are constantly earthed so the ignition circuit won't work. Another favourite is a duff condenser, that will give a weak or even non existant spark.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
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jabcb
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Re: Intermittent and lack of spark.

Post by jabcb »

Wiring diagram for the TC90 is here: http://smokeriders.com/diagrams/Suzuki/ ... S_TC90.gif
(You wiring might differ from this.)

The alternator/lighting/battery circuit is electrically separate from the magneto.

In the off & parking positions, the ignition switch grounds out the magneto so that you don't get a spark.

But you might have a bad ignition switch that works correctly only some of the time.
In the off position it might have NOT grounded the magneto but then after some engine vibration it started grounding the ignition.

Be careful when working on the electrical system.
The headlight is no longer available from Suzuki & can be quite expensive when you find one.
The bike uses the battery as a voltage regulator.
The headlight can burn out surprisingly quickly if you run the lights without the battery connected.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
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GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
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Ben
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Re: Intermittent and lack of spark.

Post by Ben »

Im battling exact same issue. I swapped out a work stator assembly and it fired right up.

So everything from the stator connection up is good. I tested the coils and get resistence on all. I replaced a diatchi condensor for an oem. The point is a diatchi and on the stator plate seems to ground out. Off it checks ok.
I really hope its not the primary coil as they are hard expensive finds.

Next step is replace diatchi point with suzuki.

Any other tests?
Ben in Canada
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jabcb
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Re: Intermittent and lack of spark.

Post by jabcb »

Ben, is this for the 75 RV125?

Aftermarket coils that are better than NOS are available pretty cheap.
Don't know what the RV125 has.
If you end up needing a coil, then need:
1) measure the mounting bolt spacing (its 80mm on the T-series & GT-series bikes)
2) spec for primary resistance & secondary
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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Ben
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Re: Intermittent and lack of spark.

Post by Ben »

Actually, for a new project 1974 RV125....had so much fun with the 1975 model, wanted to see what the 5spd version was like.

I am referring to the primary magneto coil on the stator. Perhaps the wrong term....I have a LIGHTING, CHARGING & PRIMARY (IGNITION) coil that the magneto whips around.

I know the IGNITION COIL (to spark plug) is good as like I said I swapped in a known working magneto stator plate from the 1975 and it fired up.

I would love some insight on how to bench test these copper wound primary coils on the magneto. I cant bring myself to condemn the primary coil as I don't trust my skills.

If there are Aftermarket magneto coils I can purchase, please direct me to a source.....Suzuki no longer stocks
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Ben
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Re: Intermittent and lack of spark.

Post by Ben »

Ok...point off stator plate and gap open. No continuity.

Point on stator plate, lead to condensor attached and gap open. Meter on 200 ohms I get a reading of 2.4

Attach lead, gap closed. read .4

Remove lead from point to condensor, gap open. Infinity

Not sure how to evaluate readings.....
Ben in Canada
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75 RV125
84 RZ500
85 RZ500
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Ben
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Re: Intermittent and lack of spark.

Post by Ben »

Got around to the stator again....Ended up replacing the lead between the point and condenser, as well as replacing some crummy wiring for the BLACK/YELLOW and BARE in mesh. Confirmed a good connection to the condenser top, soldered them on the last tang.

Kicked and FIRED!

Had a feeling it wasnt the ign.coil or condensor or point, just tired burnt out old original wiring with the stator plate.

Hope this helps
Ben in Canada
71 CB500
74 RV125
75 RV125
84 RZ500
85 RZ500
94 DAJIBAN
00 VFR800
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