Engine cutting out

[Jeff]

On a ride today my 78 XS1100 developed an interesting problem that I swear I have seen described somewhere here on this forum but for the life of me, I haven't been able to find.

It started while doing a long uphill stint and I noticed power falling off drastically. I nursed it to the summit and on the downhill side I killed the engine with the kill switch and when I turned it back on, everything ran normally. Later on while crusing at about 60mph it did the same thing again. It felt like I was dropping 1 or maybe 2 cylinders. Once again... blipping the kill switch off for a second and back on again brought everything back to normal. Without messing with the kill switch... the problem does not appear to go away on its own.

Like I said earlier.... I distictly remember seeing this problem described somewhere but have yet to find it again. Any suggestions where to look or what I should start digging into?

[Ken Talbot]

Check the tech article on pick-up coil wire repair

[John]

You most likely are loosing two cylinders, as each coil fires two cylinders. 1 & 4 are on one coil, and 2 & 3 are on the other. Those are the very same symptoms I had some years ago when I discovered the p/u coil wire problem. Unfortunatly, that was before this site was setup, so I had to find it on my own. Sure would have been nice to have this place to go to for answers. It's not that hard a fix once you locate the break.

[ratbyk]

Power Loss

As mentioned by Ken & John, it most likely is a broken or about to break pick up coil wire.
One other possibility from your description is a plugged filler cap vent and you are developing a vacuum lock in the fuel tank. Next time it happens pull over and quickly lift the filler cap. Listen close as it opens. If you hear a whooosh or quick sucking noise it is the breather vent hole in the cap.
Ken/Sooke