I replaced the stock plug with about 4000 miles on it with the Iridium plug. No real noticeable performance increase and I still get intermittent highway stutter. I'll be going on the highway and it'll stutter, then stop at a light, then go and no stutter. Stop again, go and then stutter. Stop, then go and no stutter. No idea. I did notice better gas mileage though, so I think the new plug must be doing something. I am back up to stock gas mileage, if not better. Filled up with 1 gallons and had about 65 miles on the odometer.

Maybe you guys can gather something from the look of the stock plug? I've heard that plug readings aren't as reliable on a 4 stroke, but still...

 

Did you do a proper plug chop? or just removed it after normal riding? It looks a bit sooty perhaps too rich? Have you done any mods? Or is the bike totally stock?

 

to me looks rich. but here check this out, might help you decide

http://www.dfn.com/benkaren/plugchop.html

http://www.youtube.com/watch?v=77bkpt7aYKI

 

Actually the plug looks a tad bit on the lean side, you only pay attention to the white insulator (it should be chocolate brown), ignore the black carbon on the metal parts.

The "stutter" that he describes sounds like a lean surge, my bike did that when it was stock.

 

Did it while stock, did it while jetted and piped, still does it with the new plug.

It's really quick and only a bar or 3 drops on the tach. It's like maybe 1-3 drops per second.

I'm going to try full 132 jet and see if that helps.

 

I think the iridium or whatever plug sucked...

I seen no advantage....After 2500 miles with it I went back to a new stock one...

Rocco

 

Which needle are you running?
Does it stutter at certain throttle positions and not at others?
You're running 88+ octane fuel?

 

91 octane, 09 dynojet needle, 3rd from the top, 128 dynojet main, stock pilot, idle circuit set, smog removed and capped, fuel screw position doesn't seem to affect it.

It's only at cruising speed on the highway, or WOT to get to that speed in the lower gears. My guess is that it's both the main jet and needle. To raise the needle is super easy and you don't have to remove the carb. It's completely intermittant and a lot of the time power delivery is smooth and normal. SOME popping on deceleration but it's not often at all. I only seem to notice it when its cooler outside.

Changing main jet is a little more of a PIA but I've heard people have been able to slide the carb in the boots and get to the bottom easily.

It's too damn cold out right now to mess around with it. Maybe next week. I'll probably do a whole tech weekend, front and rear springs, rejet, re-sprocket...

I really should just take the whole carb out and clean it just to make sure. It looked fine last time I had it out. It's just strange that the symptoms have not changed at all with a completely new exhaust, spark plug and jetting.