Misfiring on startup? Calms down after a while.

semmyroundel

semmyroundel

Club Member
Hi all, I openly admit that I haven't used my Nightster for a very long time, possibly lying dormant for 9 or 10 months.
I had previously installed Iridium plugs, but on the forum for my other bike (Yamaha), they've warned of many fake plugs out there, especially the premium ones.
I mention this because when I took it for the MOT, I noticed lumpy running with misfiring, and the guy in the MOT shop advised to take it down the motorway with a fresh fill up of super unleaded (it had some left over from before in the tank from when last used).
Whilst that seemed to cure it, even a couple of tanks later, it still does this when starting from cold, I say cold but it's hot at the moment, so cold and humidity can't be to blame.
It will run lumpy for the first few minutes, and although better later once it's warmed up, it doesn't seem to ever run smoothly as it did when new.
As I'll now only buy from Japan Spark plugs to avoid fakes, plus they wouldn't ship to uk last time, having to get a friend in France to forward them onto me, it may take a while until I get some new ones to try out.
Does it sound like plugs or could something be wrong with fuel delivery, coils etc?
It's done about 11000 miles from new bought 11 years ago.
Any ideas?
 
If a Carb. hasn't been drained of fuel prior to storage, the fuel will deteriorate and leave a Varnish type residue. This can block jets, passageways and needle. Strip the Carb and use Carb. Cleaner and a Can of Compressed Air to get rid of the crap. Not a big job. A Clean Carb. and new plugs are a good start to finding what's wrong.
Many Harley owners have said that the best Plugs are H-D ones. For whatever reason, NGK Plugs seem to cause problems. The bonus is H-D Plugs are cheaper than fancy NGK ones. :encouragement:
 
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Fill up with fresh 95 fuel and stick a bottle of redex injector cleaner in with it use the whole bottle ignore the label it will give a hot mix then put a set of new harley correctly gapped plugs in and then give it a long run non stop inc high speed motorway running it should do the trick most modern fuels have a shelf life at the pump of 8-10 weeks before they start to deteriorate due to the additives and the cetane rateing drops dramatically i did one recently that had stood for 12 months fuel injected as your is it had the same issues and that sorted it out completely your basically cleaning the injectors as you would a carb and the red ex does the entire system for you (y):cool:
 
Thanks for the replies, interesting.
I've put a half bottle of Redex through it, still no change, and it's had at least two tanks of 98 RON fuel.
I think that the plug change is a good idea-HD plugs and be done with it.
Yes, it's fuel injected. I'll do as you all say including a long run down motorway
 
Generally these type of problems start from the last thing touched. In this case suspect the plugs. NGK's seem the most popular, readily available make, but in my experience not all ways the best. Try searching out some Champions. Not everyones first choice, but they have worked for me. The fuel might have compounded the problem at the beginning but this will now have cleared the system.
 
I have ordered some plugs from Harley. I''l do the run with a whole bottle of Redex and see what transpires.
I've checked coils on my Super Tenere and am aware that they can break down, so that and the leads will be the next if the above doesn't work.
I'll post my findings here in case someone else has the same problem.
 
Hi all again, whilst using HD plugs helped enormously, it still takes a while to settle down after starting from cold.
It takes way less than at the beginning, but still I have the odd misfire until I have a couple of miles on the clock.
So should I change the leads next?
On a side note, I hadn't realised that my membership had lapsed as it previously renewed automatically, and when I tried to restart it it wanted £41 is that right?
Many thanks for your input guys.
 
watchman said:
Fill up with fresh 95 fuel and stick a bottle of redex injector cleaner in with it use the whole bottle ignore the label it will give a hot mix then put a set of new harley correctly gapped plugs in and then give it a long run non stop inc high speed motorway running it should do the trick most modern fuels have a shelf life at the pump of 8-10 weeks before they start to deteriorate due to the additives and the cetane rateing drops dramatically i did one recently that had stood for 12 months fuel injected as your is it had the same issues and that sorted it out completely your basically cleaning the injectors as you would a carb and the red ex does the entire system for you (y):cool:
Click to expand...
Told ya before……..
 
Well, another blast up the motorway with the Redex and new 8.8mm Dragspecialities plug leads and no change.
So, where do I go from here?
I should point out though I don't think it has a bearing (you tell me) it has a Lithium ion battery recently, and has most of its life had Akrapovic slip ons, road legal cans, but they hadn't caused an issue in the past.
Puzzled
 
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