I'm still here, I don't look at the message board on here very much, but I do look at tdaniels@rocktenn.com every day. I have done many of the Briggs singles and almost every one requires the same counter balance weight (this is the amount of weight that the sum of all of the parts tell you it needs) only changes maybe a couple of tenths of a ounce.
I always ask you guys about the pulley that goes on the crank that drives the belt. If it is a quality piece and you have not modified it in any way, I usually don't get you to send it. Stamped pulleys or inexpensive pulleys are rarely in balance, sometimes they are welded on and this messes them up. You can easily check the pulley by taking a wooden dowel or a broom stick, wrap tape on the wood until it fits snug in the pulley, then place it on a set of knife edged paralell pieces of metal and see if it will stay still in any position you put it in and not turn. When I say knife edge I mean a very sharp piece that the wood sits on.
As someone said earlier you can NEVER complety balance a singe cylinder engine it's not possible, but you can make it better and yes you can move the rpm up or down where they shake the worse. Al of mine are aimed for the 6000 range and may shake in the lower range,
One more thought, the base the engine is mounted on need to be thick enough and enough mass to help with the inbalance you will have. Also check under the mounting bolts to make sure you do not have a "soft foot" Place the engine on the base and try to rock it, if you gat ANY movement put shims under it to make the base as flat as you can get it.
