Started bike today, cold and damp weather. Bike started first time as normal.
Pulled away with choke still out, bike would not pull under load. As engine warmed up bike ran normal with the choke in.
I washed the bike on my return to home and then fired it up, started first time but when I rolled the throttle it started to misfire again. Once the bike had warmed up it seemed fine.
I am thinking either the spark plug leads, which have never been changed may be breaking down, or the coil is starting to go.
Any other suggestions.

 

It's cold. Probably just a carb fart. These bikes can be tempermental when it's cold out even when tuned properly.

 

Hi thanks, that did cross my mind, but this seems worse than carb fart.
If you roll the throttle it coughs and starts to cut out, until its warmed up. I recently did over 800 miles through Europe, no problems. Clean fresh fuel in the tank today.
It was good today when warmed up, but after I washed it the problem was back, until the bike was warmed up and dry.
Hence my thinking on plug leads and possible coil breaking down.

 

My next guess, since yours is a carb'd rubbermount, would be the crank position sensor (CKP). It's been known to cause problems and the symptoms mimic carb farts or poor ignition.

 

That's what the OL's '04 1200 did when the Crank Position Sensor went bad. Idled fine. No power/stall just off idle.
Part # 32804-04A. About 45 bucks.
Might as well swap out the plug wires, too. I tried that first, with new plugs. Then, put a new jet in the carb. I also took all the fuses out, cleaned the contacts and slathered them with dielectric grease. It was the CKP all along.

 

Thanks again, Crank sensor was replaced last year, different fault, bike would stop running at lights when on tick over.
I think I may have solved the problem.
Out in the garage today, bike a little damp, so before I started I sprayed the HT leads with WD40. Pulled out choke and the bike fired up, very strong, blipped the throttle, loads of revs no sign of a missing or hesitation.
Two new HT leads ordered, £8.00 each.
Im due a service soon, 40,000 miles, so all oils and new plugs.
Note to self, change HT leads sooner, but then if it isn't broke, why fix it.

 

I usually replace my spark plug wires every five years. Better that than finding out they're shot by getting zapped on a rainy day while trying to turn off the petcock!

 

The first one I put in didn't last for a year. I couldn't believe it was the CKP again. I took the sensor out of my Sportster and put it in the OL's. Bike ran fine. So I got another new sensor for her bike. That one was fine when we sold the bike. Maybe it had a year and a half on it. The issue with the CKP was intermittent. Sometimes, with a bad sensor, it would run fine.
Glad you found the problem, although I'm coming up short trying to figure out what "HT leads" are.

 

High-tension. Spark plug leads.

 

Cool. Thanks. I think I learned something.