Ignition or?

JeffB

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I have a 1980 XS 650, ran fine about 2-3 months ago and when I tried to ride it last week I could start it, it would idle but upon application of throttle would die. Bike is kept in hanger not exposed to elements as well. No matter what I did with choke, tickling throttle etc it would die once throttle opened even a tiny bit. I always have run aviation fuel in it (100LL) which is fresh, plugs are clean, re plumbed fuel lines and fuel flow to carbs perfect, carbs clean as new and I can not guess it is anything but a failing coil. Battery new AGM and fully charged too. Anyone have an idea? Thanks
 

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I've not heard of a coil going bad in that manner but I suppose anything is possible. Usually a coil either works or it doesn't, and many times they work fine cold but fail when they get hot. Once cooled down, they work OK again. But for diagnosing electrical issues, about the easiest way is to substitute a different (hopefully) good part for the suspected bad one. If you want to try a different coil, I recommend a Honda MP08. This is a very good coil that was used on many Honda models in the '90s, and you can find them quite cheap on eBay.

https://www.xs650.com/threads/honda-mp08-coil.55408/
 
If no difference left and right
My first guess charging has stopped working
Please measure charging Voltage across battery at some rev .see if there is 14 --14.5 V

edit
Aeehh sorry since it is not running you cannot do that ..But I would try to check that anyways fuse ?
 
IMO, if it'll start on choke, but take no throttle; it's a plugged pilot circuit in the carb, Clean carbs again and make sure pilot passages will pass sprayed-in carb/contact cleaner
 
IMO, if it'll start on choke, but take no throttle; it's a plugged pilot circuit in the carb, Clean carbs again and make sure pilot passages will pass sprayed-in carb/contact cleaner

I’m in that same boat. I also poke a piece of wire through and spin it around. Just to make sure there is no hard stuck on crud.
 
I have a 1980 XS 650, ran fine about 2-3 months ago and when I tried to ride it last week I could start it, it would idle but upon application of throttle would die. Bike is kept in hanger not exposed to elements as well. No matter what I did with choke, tickling throttle etc it would die once throttle opened even a tiny bit. I always have run aviation fuel in it (100LL) which is fresh, plugs are clean, re plumbed fuel lines and fuel flow to carbs perfect, carbs clean as new and I can not guess it is anything but a failing coil. Battery new AGM and fully charged too. Anyone have an idea? Thanks
If both cylinders are dying out with throttle, you'd need the pilot circuits in both carbs to be plugged. That's possible, but normally it's one side or the other.
Far as the coil... agree with 5twins... it's possible, but that's not the normal failure mode.
That is a fairly common failure mode of the TCI box though. Soon as you come off idle, the box starts it's advance curve thing... transitioning from the retard pickup to the advance one. I suppose it could also be the pickup itself. There's a disconnect for it on the left side coming out of the engine. 3 wires. You want about 700Ω on each color to black (black/white) and 1400Ω color to color. If that ohms good, I'd suspect the box.
 
Thanks for the reply’s, it starts on choke and once running I “un choke” and it continues to run fine. I did not put a volt meter to the battery to confirm it is charging but I bypassed that step and started it while it was connected to 4.5amp battery minder ( starts with or without that connected) so unless failure to charge causes some other electrical,issue I will test that. Both cylinders fire and they get hot equally as fast. My carbs look new inside and out but just to confirm it was not both jets clogged whilst idling I spritzed intakes with very short burst of ether and opened throttle, bike died. I own a bunch of gas powered vehicles and this one is a puzzler. I bought a coil from Mikexs but have not installed it yet. I once had a MGB that ran like crap and changed the coil, ran as new after, weak coils or other electrics from Lucas are not unknown To be troublesome.
 
I suppose those TCI boxes are unobtainable as well?
If it turns out it's the box, there's a guy here who fixes 'em. No new stock and the Ebay pirates want your first born male for 'em.
 
I'd check all the pertinent wire connections as well, maybe something came loose.
 
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