Can any of ya'll help with an SR500? Trying to get spark.

[MaxPete]

Hmmmmm.....dammit.

Have you checked the continuity of the HT lead? Unless I’ve slipped my trolley, it should read just about 0 ohms or perhaps 5-10 if you’ve got a resister cap on the end - but not too much higher. Maybe the danged thing is busted INSIDE the insulation.

One thing is for sure, something is wrong.

 

[scott s]

Yes, I checked it AND the coil/lead/cap is brand new. It's the correct coil for a CDI ignition.

 

[MaxPete]

Geeezzz Louise.

 

[scott s]

I tested the kill switch.
I have continuity from the connector in the harness all the way to the CDI plug on both the Black and Black/White wires. I get 0.9-1.0 ohms on those wires.

I tested the operation of the switch itself and I get:
OFF 0.4 ohms
ON Open, or infinite
OFF 0.5 ohms

I tested the key switch, going from the Black to the Black/White in the 4 prong plug.
OFF 0.2 ohms
ON Open, or infinite.

I am pretty confident at this point that I do not have a broken wire anywhere in the wiring harness. EVERY test that I do tests good, at least to the best of my ability. I'm stumped and frustrated.

 

[MaxPete]

I tested the kill switch.
I have continuity from the connector in the harness all the way to the CDI plug on both the Black and Black/White wires. I get 0.9-1.0 ohms on those wires.

I tested the operation of the switch itself and I get:
OFF 0.4 ohms
ON Open, or infinite
OFF 0.5 ohms

I tested the key switch, going from the Black to the Black/White in the 4 prong plug.
OFF 0.2 ohms
ON Open, or infinite.

I am pretty confident at this point that I do not have a broken wire anywhere in the wiring harness. EVERY test that I do tests good, at least to the best of my ability. I'm stumped and frustrated.

Well - I don't blame you Scott - and so at this point, I would sincerely (really) advise you to leave it for a day or two and step back. Then begin again when you are in a positive frame of mind. I'd guess that each of us has been at a point where we were stumped (I sure as hell have - with my dear darling Lucille ) - and in my view, that is the best thing to do.

Afterall, this is a hobby and its supposed to be fun. This SR500 issue has stopped being fun - so its time to find another issue to work on for a little while.

Perhaps you have some yellow jackets nearby....and an extra can of brake cleaner.....?

 

[scott s]

In my quest for spark, I would like to check the pulse coil. When I look at the parts diagram, it appears to just screw on. But when I Google images, it shows a short wire lead. I can't see anything on mine.
How does it attach and is there a way to test it?

My actual flywheel, pulser and pick-up magnet.

 

[Signal]

One more thing to check is the stator and pick up wiring for breaks in the insulation where the wiring comes close to the motor cases it can break down. It is possible for the wiring to short to earth/ chassis.
Is there someone near you with a working SR that you can swap your parts onto parts to locate the faulty component.
Maybe someone on the SR forum.
Nice bikes not fast but a lot of fun, I had one with discs front and rear when I was 18.

 

[scott s]

You can see the stator wiring in the last pic. I removed the sprocket cover the other day, cleaned them all up and didn't find anything.

 

[Signal]

You will need to pull the rotor and remove the stator for a thorough visual check or you could test the insulation resistance with it in situ
Before you do that...

In post # 14 from you results it looks like you are testing ignition high tension coil. From my Clymer manual ( SR 500 Singles . 1977-1979) the primary resistance at 0.9 Ohm looks within tolerance.
However the second test result of 338 Ohm you show if it is for the ignition high tension coil secondary is way off the numbers in my manual.
The secondary resistance given in Clymer is from 9600 -14400 Ohms, ( 9.6K Ohm to 14.4K Ohm). Before jumping to conclusions.
This apparent deviation needs to be pursued further, have I misunderstood your post or is that the reading of your coil. What are you using for reference material.

From the same Clymer manual the pick up coil resistance is : High speed circuit ( white/red -black) 16 Ohm +/- 30% at 20 degrees C (68F)
Low Speed Circuit (white /green-black) 87 Ohm +/- 30 % at 20 degrees C (68F).

 

[scott s]

Those 330 ohm readings are from the stator source coils, not the ignition coil.

 

[scott s]

So, what now?

Rex's said they've gone as far as they can go via email. I can send the parts in for them to test, but I'm in the US and they're in the UK. The coil and CDI are both new from them, so if the CDI is faulty, it was faulty out of the box.

I called Rick's Motorsports and talked to them today. They agreed that my numbers are all in spec and if I sent the stator in the readings would likely be the same.
The did ask if I have checked "trigger polarity". I told them I didn't know what that was and asked how to check it. They directed me here:

https://ricksmotorsportelectrics.com/blog/trigger-polarity-why-is-it-so-important/

That is the same thing as the pulse coil, no? I can't seem to get any information in the Yamaha pulse coil. It isn't even shown on the wiring diagram. I'm told it's not meant to be removed and I don't have any numbers to test against if I could.
Plus, I question if that's not what the Low-Speed pickup and High-Speed pickup tests are anyway?

In serious need of some help here.

 

[scott s]

I found a factory Yamaha manual that confirms that the low speed and high speed pick-up tests ARE testing the pulser coil. I still couldn't tell you where the wire attaches, and I'm told it's not meant to be removed. Besides, mine tests good.

I'm throwing in the towel at this point and taking it to a pro. I have a buddy that runs a shop in Charlotte. He's mostly European stuff these days, but has experience with vintage Japanese stuff and the SR500. He's agreed to take a look at it. I'll run it up after Hurricane Florence passes through.

 

[MaxPete]

Wow - that is one obstinate problem Scott. I haven't seen many issues on this Forum that couldn't be solved by the collective wisdom of the group.

Please keep us informed on the outcome of your trip to your buddy's shop and let us know what he finds.

Pete

 

[scott s]

At this point, my only guesses are that the flywheel/rotor has somehow lost it's polarity or magnetism (possibly only from being dirty/rusty on the inside? Waiting on a puller) or the CDI box is faulty, even though it's new. I did ask a guy from the SR500 forum if I could borrow a known good stock CDI box to try out.

 

[Tomterrific]

Are you sure there is no spark? Big singles are tricky and the SR500 is the trickiest. You can hardly see the spark at start, it is blue and skinny. It may have spark. Your SR will not start if the throttle is opened too much. Set the slide all the way down with the idle adjustment screw. Do you know how to use a compression release?

Tom

 

[scott s]

I do know how to use the compression release.

To be honest, I'm not 100% sure there's no spark. But I'm 99%+ sure.
I've built a bunch of bikes and can usually see SOMETHING.

I recently hooked my timing light to it and kicked it over. Saw nothing.
Kicked it over in the wee hours of the morning when the garage was dark. Saw nothing.

I'm not trying to start it yet, just trying to get spark. Haven't even introduced gas into the equation yet.