GSX400E cylinder head transplant

[garda58]

Hello everyone. I'm David from Italy. I own a Suzuki GS450ES: http://img87.imageshack.us/img87/5151/gs450daveuc7ya7.jpg
I made a lot of modifications: the last is the oil cooler circuit (http://www.motoclub-tingavert.it/ul1307/immagini/upload_user/41412_1369247072_0.jpg)
An important modification is the rear break disk instead of drum.
Now I would like to make a modification to increase the engine performance: I am studying to transplant a suzuki GSX400E 8v instead of GS450E 4v (see attachment)
and transplant GS500E cylinders. The major bore can allow me to increase valve diameter. I think that major problem could be to find the pistons to use. Had anyone experienced this type of transplant? What kind of performance can I expect considering originals Maximum power output: 41,5 hp (30,5 kW)/ 9.000 rpm and Maximum torque: 35,3 Nm (3,6 kpm)/ 7.500 rpm
Thank you very much
David

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