Hi All
My first Post

I have recently purchased a 91 NSR 250 MC21 R, but I dont have a engine for it.
I was thinking about installing a single cylinder 4/ engine, or keeping it a 250cc 2/ and adding perfomance parts.

Any ideas

Thanks
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1991 Honda NSR 250 MC21 R
2010 Yamaha YZF R6 13s
1999 Aprilia RS 154