i need to know where the cg should be set .

Which Yak there are several?

the 50 - 56 i one the first page of the site .

I don't see a YAK on the home page, just a link to the other pages with the different planes...

However I think you are talking about the Red/White schemed plane...

Please see this thread: [link=http://www.rcuniverse.com/forum/m_6414408/anchors_6418556/mpage_1/key_Yak/anchor/tm.htm#6418556]Click me![/link]

mine is the yak 50 3d red white blue and yellow with the checker board . i put a os 61 fx on it with a pitts muffler and a 12X6 prop and need a idea were to start with the cg

Yup it's the same one, just a different scheme.

That thread I directed you to has the proper C.G. in post #3.

Good luck.