My Iron smooths out nicely in 4th gear @60 mph.

 

also check to see if the stock rubber mounts on the engine have "sagged" its common for the OEM to be too soft and sag... Check the front mount bolt the one behind the forward controls... there is a NUT on the Right side that is prone to backing off.

Get the belt tension tool and check belt tension a out of spec belt can cause all kinds of vibration... like others have said check primary chain as well... these 3 things can make a Rubber mount almost un rideable on the highyway! I have New mounts on mine propperly adjusted belt and primary and i ride 100mi each day to work on all highway @ 75 and its SMOOTH as silk!

 

The rubbermount is the engine rubbermounts. The mirrors are not rubbermounted.

 

It's a SPORSTER, so it's rubber mounted, it's still a Sportster that vibrates. 'Just like the
Soft Tails & B-Engines, it's still a Soft Tail & vibrates.

 

Just developed the same issue on 2008 XL - just had both tires replaced (8000 miles) with Michelins as well as a few oil seals replaced. Mech noticed front upper eng stabilizer bolt loose and tightened it. Bike was way smoother than my old 80s sporty until the work. Took it back and he "loosened and retightened" the front eng stabilizer - no difference. Guy is a Harley trained mech, but not at dealer anymore and usually does good work. Are the torques/issues well known issues or do you recommend getting to HD dealer?

 

2008 XL1200L with 8000 mi - just started same issue. Bike used to be way smoother than my old 80s sporty but now - terrible. Two possible changes - would like to chase most likely candidate first. Both tires just replaced with Michelins and mech tightened loose bolt he noticed on front upper eng mount stabilizer. I took it back, he loosened and retorqued mount stabilizer but it still way different - still bad. Most likely belt tension or eng mount or something else??

 

I've got a '13 1200C and mine does it as well. I added rubber washers to reduce some if it initially. I then flipped the mirrors to improve the lines of the bike and still have some vibration. As others have said in the right gear at the right rpm they're clear as day. I actually use them like you would a tach because of this along with just "listening" to the bike when I'm riding at speed. When the bike is in the proper gear and rpm's the bike "sings like a sewing machine". Kind of old school but I've never had a bike with a tach so I've always ridden by feel.

 

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Also, I have found that high quality engine oil will reduce vibration better than any single thing you can do. I have used several, most will be smooth for the first 500-1000 miles then the vibration starts to set in. The two best I have used so far are Rotella and Amsoil. The Rotella was very smooth to 3000 miles, I changed it at around 3200 after the vibration was a little more pronounced. Oil was a dark honey color after drained, but you could tell it had lost significant viscosity. I switched to Aimsoil and I am still vibration free at around 3500 miles. Dipped a little out of the oil tank, color is almost the same as when I put it in and viscosity seems to be good as well. I run my bike hard and most miles are commuter with lots of stops and go's.

HD and Valvoline were black when changed at 500-1000 miles. As usual this a FWIW and YMMV. Just my observations and experience with the ole' Sportster.

Regards

Rod