Been commuting to bristol quite regularly now for a few months and putting on a lot of miles at high speeds. It seems to be taking its toll out of the SD, tyres both worn out, front wheel bearings going, something up with my front disks.

Anyway , yesterday big problems copying home. Bike had a very slight misfire coming out of Bristol, a slight cut-out and hesitation at times. Then on the motorway it developed into a regular misfire but this only happened at 5,000 RPM as you slightly rolled off the throttle. It was always the same, just one short cut out at 5,000 in 6th but I tested it out through gears and it did do it in lower gears also.

Then after a stop at a service station it became much worse. Hesitated in first setting off and stalled. Then started doing this short cutting out misfire regularly, maybe every two or three seconds whilst accelerating - always around the 5,6000 rpm mark. Made it very hard to ride.

Best way to describe the misfire is it is exactly the same as the ignition cut-out that happens when you press upwards on the quick shifter. Its a very short cut-out then back on the power but it makes a jerk in the transmission so is very, very irritating to ride with. I managed to limp the last 80 miles home by trying to stay in a gear/rev range that minimised this problem but it was hard.

Any ideas guys?

I suppose it must be ignition. Not sure where to look first or what to do, I'm not good with electronic ignition bikes and black boxes. It could be the quick shifter, of course, but I did have a look down there and can't see anything wrong but its a strain guauge HM one and like a sealed unit.

At a last resort I could take the bike to HM who are only 20 miles away and get them to have a look but if there are any wise words out there Id be grateful.

Since the bike had a few wet commutes recently I also would have a look at BGC and such. Don't forget the little connector in the front from the pick up also!
The QS is easily eliminated, just unplug it and see if issue is still there.
Unfortunately moisture and SD's don't mix regardless of the dirt bike heritage, I'm pretty sure it is something like that.

Both cylinders or just one? Start as ktmguy suggests and, if no joy, check plugs and coils.

Have spare plugs, coils, TPS, etc here and happy to help if you can/want to come here - bit farther than HM though - here today, stripping mine down to sort out my current issue, and around all weekend.

So today I cleaned the whole bike under the tank, took apart every connector and blow dried them all and put back together with dialectic grease. Nothing seemed wet inside but it was good to do this since its been a few years since I did it last.

But I did find that the wire from the HM quick shifter had somehow managed to get caught behind the chain guard and had been rubbing against the chain. The insulation had worn through and the copper wires exposed. What I don't know is whether this wire has only one wire or maybe more and they have all got mangled up and shorting out intermittently. I rang HM but they were shut and I just got an answer phone. Does anyone know what should be going on in this wire? Im tempted to cut the wire at a good point and see whats going on inside. If there are one or two distinct wires or more then I can cut out the mangled section and solder them all back together again.

I taped up the wire as it was and the bike started up OK.

Went on a test run and at first it seemed cured, no problems but then the cut-out problem/ misfire returned. But I also realised that the quick-shifter doesnt work all the time either, it sometimes does but then stops. I suspect all these problems are related.

Bummer because as I work in Bristol now I have no easy way in the week of getting the bike to HM to sort out, even they are only 20 mins away. I looked at the way the quick shifter is wired in, (HM did it about 5 years ago) and its complicated - wires to the ECU, the control box and each spark plug. I don't think I can just unplug it easily, I don't know what Im doing.

As a quick fix you could cut the damaged bit of wire out and tape the ends securely away from chain/sprocket etc. No quickshifter, but it will shift fine without one till you can get sorted.

I cut out the damaged section and discovered there are two wires. I soldered them back together, insulated them and then shrink sleeved the joint.

Bike still got as bad misfire and now only runs on one cylinder.

I've tried everything now so I guess I have to find someone who knows what they're doing with electrics. I'll give HM a ring in the morning.

Comrade Bic: I did notice that the cable was shielded. That's a bit unusual insofar as I would have expected just regular twin core or even more cores. The fact that it is shielded indicates (assuming it's original) that HM were a bit concerned about inductance. Was each of the cores shielded and did you replace the shielding when you re-soldered Etc? If not, possibly whatever is happening on one core is affecting the other.

Another thought - given that the cable was getting snagged near the spocket is it possible that it has tugged the cable and you have not got a good connection up at the ECU?

all so did u connect the out wire shield back up that could be the earth

Bic,I had similar misfiring issues and I knew it was my DynoJet QS because when I disconnected it the problem was solved.The reason was the gear shift lever had come loose(a commen problem for me specially at track days and as the linear QS rod is connected to the lever it was killing the gas randomly as the lever was vibrating up and down.I have now drilled and wired the gear shift lever bolt and all is well.Cheers