Alan,

If you got your motor from Iconic, that is one trick bit of kit right there. I have only owned MC21/28 but AFAIK the MC21/28 cases should fit in MC18. I know the pickup wiring harness is different from MC21/28 to MC18. Doesn't mean it wouldn't work. Slight timing difference between MC21 and 28 flywheels, unsure if MC18 is different as well. You'll have to check oil pump connectors between your MC18 and MC21.

You should compare MC21 to MC18 wiring diagram to figure this out.

You should also do a leak down test on the motor (if its from Iconic).

I have a comparable motor in my MC28. I'm happy to give you my jetting setup. Well.... my motor might be a bit tricker than that Okuda built motor.

Scott
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MC28SP, '16 KTM 500EXC, '16 Beta Xtrainer, '07 BMW 1200GS, '96 Ducati 900SS