[crisp330]

I recently had an issue with my bike having a dead miss (one of the cylinders wasn't firing). I replaced all the spark plugs and it rode fine for a couple hundred miles (only thing was the idle jumped around a bit) but yesterday I took it up to the mountains, it did fine, but on the way back it felt and sounded like it had the same problem as before. When taking off from a stop is when I really noticed it, once up to speed to seemed to be acting normal (we were doin 90mph+ trying to outrun a storm... no problem with the bike)

It didn't always do it though, sometimes it felt OK. I just got back from a short ride to see how it would do and it did fine too. Whats going on here?

Also, I wanted to run some injector cleaner through it (don't know if this could be the problem but it couldn't hurt, right?) and was wondering can I use the same stuff for a car or do I need something for a motorcycle specifically? Any recommendations?

The bike running normally:
http://www.youtube.com/watch?v=erlXH-tUMqY

The bike when it had a dead miss (and how it sometimes sounds/acts now):
http://www.youtube.com/watch?v=3-gMeFeO8iM

The bike & idle after I replaced the spark plugs (after the video above):
http://www.youtube.com/watch?v=EVPKAELs4pY

Thanks!

 

[crisp330]

PS the bike is stock except it has a 2006 shorty exhaust can on it with the baffles removed. Everything else as far as the motor goes is stock as far as I know.

 

[nitrosportman]

coils? bad spark plug wire? my only thoughts

 

[cj360v8]

^ yup, that's what my thoughts were as well

 

[crisp330]

so for the coils that would make it sometimes feel fine and sometimes feel all jacked up? What exactly am I looking for in the coils to tell if one is bad or not? And any thoughts as to why it used to always do it but after spark plug replacement it only starting doing it sometimes after a couple hundred miles?? Thanks... I'm just really baffled on this one.

 

[cj360v8]

Well, if a coil was going bad, it could only act up sometimes. Same thing with a plug wire. If the conditions are right, it works fine. Change the conditions, and things go bad. Easiest way to check plug wires is to run the engine and spray soapy water on the wires. If they're bad, the engine will start running rough. Coils are little more difficult to diagnose.

As for the spark plug change helping things temporarily. They've probably become fouled from not firing and it's become more common due to that. You should be able to find out which cylinder isn't firing based off of what the plug looks like. Then, you'll have narrowed down which wires, or coils or whatever you need to check.