Mavve har en zxr 750..
900B-motorn, den från 94-97 ska passa rätt bra utan några större modifikationer.
Nyare zx9-motorer ska väl vara mer eller mindre omöjliga att få i.
*Edit: Men kolla med Mavve.

Det är väl liknande modifikationer som krävs. Hehe.
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"I have just fitted a B model zx9 engine to my 96 p2. I've used a kit from
http://www.brgracing.com to relocate the two front mounts. This avoids chopping the mounts. You could of course oval the engine brackets on the motor. Remove the emissions and use the stock exhaust. I'm fitting a full titanium akro,+4 advancer,41mm cv zx9 carbs with stage 1 jets. Expect 140bhp"
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"Couple of methods, you can buy the BRG racing kit, you can cut the front engine mounts off and reweld them in position, or you can find a competent engineering firm that will make something similar to the BRG kit but without the expense!!
you will need the engine, carbs, airbox (but a modified , airbox mounting plate), possibly a longer throttle cable, transmission. CDI/electronics are the same, only difference is that the CDI on the 9 (or the 7 one of them) is a grand more! may need a radiator bracket, and radiator fan due to close proximity to the headers.
Use the 7R headers, 9R headers won't fit! oh yeah and you need the reservoir (radiator) bottle off the 9R too!"