Track Tac

what is a GEM motor

Vintagequest said:
Once I enlarge the photo it gets kinda fuzzy but the kart is a Margay Concept. Engine is a McCulloch with a GEM box muffler. Does the engine have head bolts? If so, it is a 100cc engine. If not, it is likely an 80cc engine.
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I've seen some fixed head 100 cc saws also, but they are very few and quite rare anymore. The most common useful fixed heads are 80cc and 87cc. They have different stroke lengths. My heavily modified 87cc fixed head will run with stock 100cc Mac removable head kart engines all day long. The 80cc Mac 250 Saw is very similar to the Mc49, but does have a slightly different sized combustion chamber depending on which incarnation of the Mc49 it is.

But I guess the real point is, if it is a racing McCulloch engine and you buy it for a yard kart. Take the engine off and sell it to a vintage karter, you'll likely make decent money off of it.
 
Vintagequest said:
Yup. Quite a few vintage guys loving that chainsaw engine class.
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For good reason. The saws are plentiful and relatively inexpensive, MaxTorque has a good clutch setup for the crank that is different than the kart engines. But you still have to do all of the work to make them work, just slapping pieces in them won't make them work well.

And part of it is that the older Macs are not as plentiful, and the fewer of them out there, the fewer that are raced. Need an engine supply to keep this going. Just look at Sportsman Rear Engine at the VKA events, hardly anyone running that class with old 6.1s and then you get the occasional West Bend 820. Last event there were 3, with one being an 820. Quincy there were 2, one was an 820. Brodhead had 4, one was an 820. I ran at New Castle where we had 5 and 2 were 820s. That class should be more populated than that as its one of the most simple classes, don't have to turn big rpm with a pipe and risk sticking them, but the old Mac 6.1 restriction kills it.
 
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