G'Day. Can anyone help with some advice on a possible cause of a misfire with my 1980 XS1100. The old girl idles fine ( most the time ), accelerates fine ( except from low rpm ), cruises fine ( most the time ), BUT it has a misfire, where it looses spark to both 1/4-2/3. Only momentarily but annoyingly , I've replaced TDI ,checked coils, checked negatives checked pick ups , checked timing - carbies are good and working fine, I'm sure it's in the ignition but can't find the problem - if I weren't already bald, I would be now. Any help would be great

thanks

If its loosing spark to , both 1/4 and 2/3.   them its got to be from the pick-ups shurly ,  I would swap them out, or the lead  out of the stator,

Howdy.

Thanks for the reply.

i have checked to pick up coils with a meter at the TDI and both seem to check out in spec.

I connected a negative lead from the battery to the TDI and also from the battery positive to the positive(12V) input on the TDI. But there was NO change in the miss fire. I did this to rule out a possible loose connection at the bars or a dicky switch.

I also checked the voltage at the TDI while the bike was running. At idle it was only around 9V and as you increase the rpm the voltage dropped to around 7.5V. Hence I tried bypassing the switches etc. Also disconnected the emergency tilt switch. 

All these things are making little /NO difference to the problem.

The hike is quite rideable but annoying / frustrating and just shouldn't behave like it is.

The old girl idles smoothly and seems to miss when the throttle is rolled up.

As I've said it is becoming very frustrating as there has to be a reason it's doing it and thus a fix for it.

Regards

Mick

Just to throw it out there have you thought that it might be a fuel problem? rather than an electrical fault, I only ask as if it only misfires when your out on it it's difficult to tell the difference between a misfire and a fuel starvation problem. As I said just a thought.

Does it happen all the time or only when hot. I had an xs11 and coming home from Ireland one time in the pouring rain (what else) the same fault showed, and got steadily worse. When I eventually got home and checked it there was a hairline fracture in one of the coils. Obviously when hot it expanded allowing moisture in. New coil no more issues

G'day Jimmy,

thanks for the input

I'm fairly sure the problem is in the ignition system somewhere.

I bought some High Tension lead today and will grind the existing leads out of the coils and replace them even if it doesn't fix the problem, at least it will be another possible cause ticked off.

Clutching at straws but running out of things to look for.

The miss doesn't seem to be temperature related as it occurs from initial start up

thanks again

cheers Mick

 

I also checked the voltage at the TDI while the bike was running. At idle it was only around 9V and as you increase the rpm the voltage dropped to around 7.5V.

Mick

Sounds like a charging problem,  ,or in need of a  new battery , . good battery shows 12.6 +  ,