Although some of his dates and information are contradicted by some of the pictures I have found, Rick Loving posted a history of the Chevy Jr. on the Corvair Center web site. He stated that:
“Some time prior to 1965 GM contacted Rupp MFG, a mini-bike and go cart company located in Mansfield Ohio, to provide a chassis for a miniature fiberglass replica of the Monza SS show car. Rupp ended up paring one of their existing models of go cart chassis, the Dart Kart with the scale replica Monza SS body which was then designed to fit the Dart Chassis. The single seat Monza Jr. was powered by a 3.5 HP Lauson motor (a division of Tecumseh). The body had integrated inner fender wells to keep out road debris. The steering consisted of a uni-action steering linkage and braking was handled with a 6” drum and brake strap setup common to Karts. The drivers ride comfort was enhanced by inflatable rubber tires and a black padded naugahyde seat with front and side bolsters. It would appear that the first Monza Jr.’s were offered with black seats and the later Chevy Jr.’s were offered with white seats.
In 1965, Chevrolet received its first order of Monza Jr. go carts from Rupp. Chevrolet displayed them and raffled them away at auto shows and exhibits. It is believed that they first made their appearance at the Detroit Auto show, possibly in conjunction with the newly restyled 1965 Corvair debut and then continued to make their appearance at various auto shows, traveling Chevy shopping center shows, Chevy exhibits at fairs, etc.
Initially they could only be won through these special promotions, but eventually Rupp was allowed to sell them to the general public. Not only could the general public purchase them from Rupp but also dealerships began buying them and offering them in their own promotions as well.
Over the years there were some slight changes made to the carts. The very first carts produced from 1965 to 1967 were named Monza Juniors and were Ember Red like the full sized Monza SS prototype they paid homage to. There are two different styles of Monza Jr. cart bodies.
The first generation carts manufactured were similar to the Mitchel and Jordon cart body, in that they had the raised “hump” behind the driver (as compared to later styled bodies) to allow for a taller rear seat. A windshield option was never offered by Rupp and was only seen on the two GM specialty carts. The 65-67 Monza Jr carts came with a 3.5 HP Lausen motor and all other standard Rupp Dart options. This particular body style was produced in a much lower quantity and only a few are known to still be around. The cart was offered with an optional triple white stripe decal (2 narrow on either side of wider center strip) running down left side front to rear. This was a lower quality tape, most often peeled off or missing once exposed to weather. The carts came with a black license plate with Silver Bowtie and Monza Jr. script and red reflector faux brake lenses. The instrument cluster area had decal with Monza Jr. and a Chevy bowtie in the lower right hand corner of the cluster panel. Sometime after the initial production run of Monza Jr bodies, a re-design of the body occurred. This 2nd generation body kept the main body lines but changed the rear deck area behind the driver, the cockpit back shaping was lowered and the high of the seat was changed to accommodate the new height of the cockpit area behind the driver. Both the 1st and 2nd generation bodies had a molded area for the Monza cross emblem on front nose of the cart body. The Monza Jr.'s have a serial tag riveted onto the body, in the drivers "cockpit" area, generally on the passenger side.
In 1968, there was a 3rd generation body which consisted of a very minor body change removing the raised area on the front nose where the Monza cross was placed on earlier versions. Additionally, the cart’s name was changed to Chevy Jr. and the body color was changed to Marina Blue with a wide horizontal white stripe pattern added to the nose and rear end. This white stripe consisted of a thin stripe and a thick stripe with the words CHEVY JR in black print. Early Marina blue carts came with the Lausen 3.5hp motor, but sometime in 1968 Rupp switched to using a 3.5hp model H35 Tecumseh motor. The H35 would be used in all future carts. It would appear that early production (if not all) of the Marina Blue Chevy Jr. had the serial tag riveted to the passenger side like earlier carts.
Sometime in early 70’s the Chevy Jr. body color was changed to Corvette Monza Red (a red with more orange color tint) with similar white stripe on the nose and tail. However the stripe now had the script Chevrolet printed in black instead of the print Chevy Jr. Chevrolet continued to use the carts in promotional give-a-ways up until around 1975. The Monza Red Chevy Jr bodies did not have a serial tag affixed to the body and only had a visible serial decal placed on the frame of the cart . A stamped “hidden” serial number can be located on this Chevy Jr frame on the left side, "floor pan", between the main frame rail, and the outer rail where the body mounts to, close to the front of the pan.” (
http://corvaircenter.com/phorum/read.php?1,892456,892490)
More info can be found here:
https://www.vintagekarts.com/monza_ss.htm and
https://bangshift.com/bangshiftapex/rupp-chevy-monza-jr-go-kart-found-craigslist-coolest-kart-ever/1st picture: Chevy Jr Giveaway Detroit Auto Show (enlarged to show red color) (cropped from
http://pilotcarregistry.com/rare-vintage-photos.html)
2nd & 3rd pictures show a Chevy Jr today (
www.hemmingsmotornews.com)
