cough under heavy load

2006 Classic. Has aftermarket Triumph exhaust and was tuned by dealer for it. I have the eager beaver relay kit installed and also Pig9r's undertank K&N. Did the 12min tune after the K&N install. Everything ran fine till tonight.

Just tonight I encountered a cough (miss) during heavy accel up a 10% grade. This was at cruising speed of 75 or so. I also later encountered the same behavior when rapping out the gears from standing stop.

The gas I'm running is 89 octane and has StaBil in it.

Ideas?

Thanks,
Bill Montgomery

I experience something similar on one of my Harleys a few years ago. It ended up being a pin hole (smaller actually) in the fuel line. Any chance you pinched yours? Also, you might try re-doing the 12 minute tune.

How old are your Plugs

plugs

unknown, bought the bike with 29k miles....presume it was ready for 30k mile service.

fixed but unknown

I thought maybe I had bad gas, so I ran it to as close to empty as I dared and then filled up with 93 Oct. No improvement, in fact worse. It was now missing on almost any acceleration at all. When I got home, I pulled the bearclaw and lifted the tank and wiggled everthing I saw. There is some kind of a sensor plugged into the front of the plenum....it had pulled very slightly out. I pushed that back in and played around with placement of the vacuum lines. Anyway, next test drive problem was completely eliminated. Accelerated from 75 right on up to a hundred very smoothly. My money is on a pinched vacuum line.