For the newbies that went this far into this topic about vibration and performance enhancement this is the time for you to assess your own mechanical skills, your time as well as the tools you own to actually do it.
This long topic is littered with people that bought parts but have not installed them.
'Cracking the case' on your new little 2-stroke is not that easy, putting it all back together the right way the first time is even harder.
If you just want a reliable motorized bicycle that will do over 30MPH with a 66cc while sitting up without making your hands vibration sore after a few miles this the simple formula I use for my 'showroom' bikes for local sale:
-A good steel bike with dual brakes, I like Macargi Pantera's of late.
-A 2012+ Grubee GT-5 Skyhawk engine kit.
-Get the extra front mount kit or get an SBP front mount for your front tube size, Get an Iridium plug and dual pull brake lever at the same time.
-Bolt the motor on with metal to metal contact, no rubber or padding or other crap between the mounts.
-Strip the handlebars, a box cutter works well for the grips if they are stubborn, then cut the hard plastic off the throttle barrel and toss the left side one away, those hard plastic grips really suck bad and why your hands hurt.
-Get a set of BMX style foam grips, remove your throttle barrel and 'milk' the new grip on the throttle barrel.
-Attach the parts back on the handlebars for easy logical use, dual pull brake and throttle on the right, shifter (if you have one), clutch and other foam grip on the left.
-Replace the stock wire from the Magneto to CDI with some good fat gauge wire like outdoor extension cord wire and use an Iridium plug.
-Run fresh premium gas with the proper oil mix (2/3 cup break in, 1/2 cup per gallon after).
Sure, the motor may still have slight vibration but nothing like what BGF and other old motor kits have, and you just don't feel it at all with foam grips.
The way I see it pushing these little 2-stroke motors beyond intended limits with expensive add-ons for a couple miles an hour direct drive is just silly if involves breaking motor case when just an X-chamber pipe will do most of that, and if you really want to ride scarey quick or fast do it with gears like a shift kit and run your motor in it's normal RPM smooth sweet spot.
For the hard core wrench turning hobbyist with cash to burn all of this is great info and cool stuff, I am just trying to point out to the rookies you just don't need all these hard to do 'improvements' to build yourself a nice reliable comfortable to ride motorized bicycle is all.