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building a gk1200,have an original stock mc7 with stock clutch (9 tooth), i am wondering if anyone can give me size(number of teeth ) for a low range ,mid range,and high range sprocket. not sure which way i want to set up yet, that's why asking for all 3. any help would be great and everyone have a good and safe day.

Hi Ed. Welcome. Couple of questions. Where are you going to run this? If it's a track the length of straight. How much do you weigh 125 lbs or 250 lbs?

weight is 185lbs. , not really sure where its going to be run,probably a track, but not racedat thi time. want to get an idea on gearing, low, mid, and high

76-77 High

70-71 Mid

63-64 Low

Basing those off of a Mc91 at about 180 lbs.

R.E.A.R.

Bob, his non-boost ported Mc7 will develop 2-3 horses less than a '91, and less bottom end with the small carb. It may need 2 or 3 more teeth on the bottom gear than a '91. The '7 needs to wind up. Ted

Tire diameter will play into selection also.
Need to keep ground clearance in mind when going with a large tooth count out back.

R.E.A.R

Bob is right. Smaller rear tires is like adding teeth to the bottom gear. Back in "the day", I typically ran 4" Go Power magnesium rear wheels with the smallest diameter 10" tires I could find. This was with a modified, high revving stroked Mc10 on alky. The combo worked very well. Even my Pop, who weighed 260, ran the 10" rear tires in A Super Heavy class. We also learned that short tracks liked the narrow rear slicks on the lightest rear rims we had in the shop. Rubber weighs more than magnesium does. I admit, we were running direct drive back then, so no clutch meant lower rotating mass, smaller brakes relied on the direct drive to help slow us down. The Go Kart 800 and the next year, the 1200 did not hurt either. They went where you wanted them to go with far less steering effort than our previous Bug Wasps did. TJ