You'll have just as much bother fitting RS250 heads as you will welding & machining MC18 heads to get the plug in the middle.

The gain won't be as great as you imagine either. It's not a weak point on the MC18, although HRC did produce heads for both the Mk1 and Mk2. By the time the MC21 came out they must have realised it wasn't worth it though, as none are available for the later bikes yet they still make better power.
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!