if i put 60 size asp engine on 50 size YAK model then how is the 3d performance?
have anyone used this combination ?

My experience putting a OS52 two stroke on 46 size plane are the following.

1) Awesome power, can hover at less than half throttle.

2) The landing gear flexes during landing (especially a bit hard landing) due to the added weight.

3) Due to [2], changes of prop hitting the ground are there.

4) Drinks a bit more fuel, flights are shorter.

5) Chances of the plane being nose heavy are higher, may have to compensate for that.

BTW, putting higher size engines are common, when the engine used is 4 stroke.  People routinely put 55 stroke engines on planes that are meant to be 46 or 50 size.

then putting 52 size asp engine good on a 50 size plane i think...

I have seen people putting OS .55 AX on .50 size pattern planes for additional penetration and speed.  I think thats the maximum. 

Moreover, the YAKs are mostly 3D capable models (with the exception of some).  Hence they need to have minimum wing loading.  Moreover, when wing loading increases, the stall speed also increases, hence low speed harriers become impossible.

I have heard of people ripping off wings on their Funstars (3d funfly plane) midflight by using a .60 engine instead of a .46!  This is because of excessive forces and speeds which these planes cannot handle.

An ASP .52 would be ideal for a full blown 3D YAK meant for a .50 engine.  You would keep the plane lighter and hence it would perform better.  Try flying the same plane on two setups.  One heavy and one lighter!! You would immediately like the foamy feeling you get out of a lighter setup!!  Glide would be better.. Harriers would be better.. Hovering alone might require some more power!!  Landings would be floaters with real light setups!! 

If at all you want to use a .60 engine, then go in for lighter battery packs, carbon fiber upgrades for landing gear and tail wheel.. foam wheels instead of rubber wheels, smaller fuel tank etc..  The servos and the electronics should also be moved back to accomodate the heavier nose weight!! 

Experiment with different setups till you get it right!! Thats the only way to get a full blown perfect 3D setup (unless a similar setup is already tested and flown by someone else)!!

Then, what YAK are you referring to?? Which brand?? If it is CMPRO, then it is not fully 3D capable.. atleast thats what I noticed from the model after seeing it fly as well..  keep us posted on your decision!

- Chan

its a bombay rc product.
here is the link
http://bombayrc.com/product_info.php?cPath=21_25&products_id=64