I am a bit at my wits end here.

I've got a 77 xt500 that refuses to make sparks.

New points, new ignition coil, rewound stator source coil, yet no fire. very frustrating.

I know this is about as simple of a system as they get but for the life of me I can't get it to fire.

I have tested the source coil - resistance reads 2.2 ohm - spec is 2.13 when I kick over the bike I can generate up around 10v out of the source coil. - that should be enough right?

points are set up correct. - the gap is set at .014" to spec. timing is correct - opens just as the flywheel passes F mark.

I have checked the wire coming out of the points and with the ohm meter it reads infinity when they are open and 0.0 when they are closed. so this i believe means they are working correctly.

I've just installed a new ignition coil from Kedo. It tests a bit out of spec, but so did my last one.
0.9 ohm small wire, and 6.1K ohm on the HT. the ground also checks out ok.

Also, I have attempted to eliminate the ignition switch and kill swith by bypassing them and connecting the stator wire and the points wire directly to the coil.

Also, new plug and new plug cap ( measures 5.1K ohm)


Still nothing.

Anyone out there have any more ideas.

I know this type of problem has been posted before and I've read a ton of stuff, but i still can't solve this.

Any words of wisdom?

TIA

WCR

Does your bike's ignition system have a capacitor? Only thing you've not mentioned.
So if it does (mounted on the contact plate?) it's probably that.

Best of luck.

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TTR250 - London to Cape Town

Oh yeah, forgot to mention that, new capacitor as well, but I am pretty sure the bike should make sparks regardless.

I've check the resistance of the points wire as well and it looks to be fine, almost no resistance, but I haven't replaced that yet either.

What do you mean by points??

Anyway, some kill switches work "the wrong way around".
When you engage the kill switch it JOINS the two cables!
When you disengage the kill switch is separates the two cables thus allowing the bike to start!

Separate the kill switch cables and try again!


Vando

Is the stator source coil on your bike in a fixed position? Or does it have to be set to the correct position for timing? (Timing of pulse relative to contact-breaker opening?)

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TTR250 - London to Cape Town

Points=contact breaker. Kill switch is not hooked up at the moment. Also when kill is off it just grounds the ign circuit.

The stator is fixed to one location, the flywheel magnet runs around it.

I guess I need to know if 10v out of the stator is enough to fire the ignition coil. I can't find this info anywhere but does anyone have a clue what voltage range this should be in. I found somewhere a mention of 35-40v when the bike is idling but no mention of what it should be when kicking it.

How about - disconnect the stator coil and connect up a 12v battery.
Manually open the contacts - there should be a spark.
If not, something's still wrong in the points-coil-plug area.

If you get a spark, maybe the stator coil side isn't right.

Finally, is there a good earth contact, HT coil body to frame?

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TTR250 - London to Cape Town

Well I've now replaced all the wiring, to the points, ign coil and stator. And I do get a very weak spark but also very intermittently. It sparks only if you hold the plug against the head, and them only about every fourth or fifth kick.
I did manage to get it to run, but only for a few seconds at a time.
I've switched the new ign coil with the old one and have the same results, I switched the new condenser out with the old and also the same results.

I tested the stator out put on my xt550 which is also a magneto system and I get about the same amount of voltage from it, around 10-12v while kicking. I did this just to compare what the out put was like.

Guess the next thing to do is try and get a new stator, or a replacement to try out.

Any more ideas? Before I buy some 150 buck old stator off eBay?

Yep, that's normal. You have to earth the plug, usually against the head.

But once every 4 or 5 kicks isn't much good.
Don't know the set-up on your bike, so when you say - find a replacement stator - do you mean the set of coils that provides power to charge the battery etc? Or does that include another source coil? Maybe that's the problem.
The coils that send power to the battery don't normally affect the ignition circuit.

One other thing, and I have no experience of this, is the rotor still OK regards magnetism? I see there are places that will "re-magnetise" a rotor, but I've never had to have this done.
Don't know how you test for it, but do spanners and screwdrivers stick firmly to it, without any encouragement?

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TTR250 - London to Cape Town