[skidlids]

Picked up a 8500 mile late 583cc Monster engine in October off Ebay for less than £300, then picked up a similar engine on New Years day for less and the guy had older 583 engines sat on his garage floor,
I'll dig the contact details out

The 1998 Monster engine in Dallas's 583 cost me £250 and without any carb work, cam timing or a like, just belts and oil/filter he was able to run at the front with Harriet at Cadwell.

The PB bike that Luke rode to a podium at Mallory had a bog stock engine, again not even a Dynojet kit and I doubt if the engine had been apart since it had left the factory in 1995.

As Paynep (humouros post Paul) well knows spending your money on track time can reap better rewards than spending it on the bike
ask yourself could another rider get your bike around the track quicker than you, if the answer is Yes, work on the riding not the bike

The problem isn't with balancing as I believe there is little to be gained for the cost involved, its the modification.
As there are two types of Crankshaft
1, unmodified
2, modified
the second group can include lightened, knife-edged, stroked and balanced, so for policing reasons Unmodified is the way to go