http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/5CarbSync

has one link, to a forum entry with no details any more.
and other links, to pictures that dont exist any more
can we get it updated to something useful please?

Found the balancer picture you want on my computer,

Hey thanks!

I uploaded it as an "attachment" to the wiki. but dont have edit perms, so couldnt update it further

Another option, and this one is used all over the world on other air cooled two cylinder engines with great success:

http://www.powerchutes.com/manometer.asp