McCulloch engines.

[Russ Smith]

I feel funny asking thjis because I've been around Vintage karts for quite awhile but....................what is the difference between a "Super" like an MC30 and one "regular"(?) like an Mc7?

[Bob Alexander]

Mostly ball bearings on each end of the crankshaft, and side covers...

[Mark Loraine]

and with the exception of the "non-super" MC92 and MC93 that also had the dual ball bearings on the crankshaft.

and the MC91 M/C minibike engine

[Rob Voska]

Tin head shroud vs cast side cover is another.