M.L.S.C.

Drewpy, and where would that box be? On the under side of the battery tray?

What Drewpy said, had the same issue with my bike. As for whether tis serious - when trying to kickstart my bike it backfired through the carbs (hell if I know how or why, as my coils seem dead), and caught 'em on fire, flame was small and with no fire extinguisher anywhere nearby and two fairly expensive and fairly new cars within 5ft from the bike I had no choice but choke the flame down by covering the carb intake ports and thus cutting off the oxygen supply. I got lucky, you may not be as much - pull the carbs off, check the float level. Also check the fuel tank selector valve as it should shut off fuel when left in the "on" setting with the engine not running - tis a vacuum diaphragm inside taht runs off vacuum, engine off means no vacuum and no vacuum means no fuel, or at least it should, if all is working properly.

I have no idea, the bike is 1980 so I think it should be using not the "points" (contacts?) but the newer system - coils have plastic plugs with spade connectors, vs. the older style individual bullet connectors, if that helps. When I remove the cap on the left side of the engine above the spark plug, there's a 2-blade rotor on the camshaft with something black around it with a single metal "notch", looks much like the magnetic pickup coil thingie in a Ford Duraspark distributor, and has only three wires coming off it.

So 12V key-on at the red/white wires is good, but 12V on the other set of wires should actually be ground? (coils unplugged, so no current flowing through them) I take it as the contacts cover you mention is the one on the left head of the engine, right above the spark plug? can you post a picture of how it should go in, and what I should look for, in terms of it being flipped around or something? Cause I've had that off before, and I didn't find nothing weird, but then again I probably didn't know what I'm looking at...

Thanks Mervin, that's exactly what I did, and it worked nice! However, I'm still having a no spark condition, so I measured the voltage at the power leads from the main wire harness, and I got steady 12V with the key on. That is 12V on all four leads (two per coil), both the red ones and the orange ones! I'm pretty sure that ain't normal, so what could cause it? Any ideas?

I just ordered a pair of coils, wires, and NGK plug caps from Mike's XS in FL. Great, but there's a twist - the wires don't have the caps attached to them, they all come separate and I'm supposed to put it all together myself. Well, I ain't never done such a job before, so can someone please enlighten me - how do I attach all those pieces together? Thanks!

Aight, so I installed the coils and wires, plugged them in, can't get any spark, swapped the plug wires, still the same deal. Buddy says tis cause I'm using the 4-cylinder coils, he claims they make much much weaker spark than the 2-cylinder coils - does that make any sense to y'all? I mean I apparently get some sort of a weak spark as it managed to backfire through the carburetors and catch the gas-flooded air intakes on fire (very small flame, more funny than dangerous), but that 's about it, don't wanna fire the cylinders and that's that. I think I'll have to take a trip to the Yamaha stealership after all, and shell out the bucks for new coils and wires... Unless y'all got other suggestions? Also how much of a price tag shock should I expect for two coils and plug wires?

Thanks Dave, that's good to know. I'd assume my XS400 also uses the wasted spark ignition? Coils are direct plug in at the harnesses.

I got a pair of ignition coils off an 1981 XJ650 that I'd like to use on my 1980 XS 400 Special - the XJ coils have two wires coming out of them, one fires cylinders #1 and #4, whereas the other gets #2 and #3 - does anyone know what the firing order for the XJ is? Do the cylinders fire two at a time, (so #1 and #4 together, then #2 and #3 together), or there is an offset in the firing time? Thanks!