Been wondering what the current thinking is on the notorious R100 3000-400 RPM vibration. Over the years I've read scores of threads from both ADV and other forums on this topic and there are varying opinions as to why this common characteristic exists. Some have postulated that the added weight of the pistons accounts for the increased harmonic vibrations and others point towards imbalanced rods and pistons, flywheel/clutch assemblies, imbalanced and misaligned crankshafts, mal-adjusted timing, carb balancing, etc.. Whatever the cause, it really seems to be a common characteristic of this particular displacement and engine configuration. I've had four R100's...an 83 RS, 82 RT, and two 93 RS's...all completely stock. The 83 RS, 82 RT and my current 93 RS each had the 3000-4000 RPM vibe. The 93 RS I let go approached R80 smooth but I have no idea why (I should have kept that one!). Of the R80's I've owned (an R80/7, two 87 monolever's, an ST and a g/s) all were very smooth. I'll also include a 75 75/6 in that bunch as it also had a very smooth motor. I should acknowledge that "smooth" can be somewhat relative and subjective. I once had a guy who had only ever ridden R100's and took a ride on my current RS and told me it felt "surprisingly smooth". I also rode my RS from NM to PA with a buddy who had a K75S during which we swapped bikes quite a few times. We both agreed the RS was markedly vibey in comparison but that the K75 was actually too smooth! I love the extra power I get from the R100 and 5000+ RPM is sweet, but the R80 engine has spoiled me and I find the 3000-4000 RPM vibration quite annoying and I'd like to eliminate or minimize it if possible. With this particular bike it really gets pronounced around 3500-4000. I'm wondering what the conventional thinking is on making a 1 liter as smooth throughout the rev ranges as all of the R80's I've owned. Please don't bother with the obvious...I already try to avoid riding in this rev range and I know how to properly tune an airhead. What I'm looking for here is a viable mechanical solution/remedy for this issue. Thoughts?