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In 1968 Yamaha turned its attention to building snowmobiles. Originally a small number of sleds (only 300 total that first year) were sent to select dealers to ride, test and show to potential customers. These sleds were then to be sent back to Yamaha’s factory at the end of the season as Yamaha ramped up to jump into the then rapidly expanding snowmobile market.
Some of those sleds didn’t make it back to the factory though. Vintage experts estimate there may now be about 12 complete 1968 sleds out there, with other parts and pieces still to be found.
A couple of my neighbors, Warren and Lynn Grundeen in Isle, Minn., have a great Yamaha snowmobile collection. They have one of those original 1968 SL 350s and a lot of 1969 Yamaha SL 351s, and still ride them when they get the chance.
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The Grundeens assure me that those early 1968 models were considerably different from the ’69s. For instance, the ’68s had a 350cc 2-stroke motor that created 23 horsepower, but in ’69 Yamaha came up with oil injection, which was driven by a small belt off the crankshaft, right behind the drive clutch. This was an industry first, but now it’s standard on all 2-stroke sleds. The motor was called a 351, that’s why the model became the SL 351. By 1970 there was an SS396 twin too, creating 36 horses.
The 1968 sleds’ 350 motor had pork chop crankshaft wheels, a different ignition system, recoil, fan housing, cylinders, and drive clutch to name a few differences between it and the ’69.
Additionally, Yamaha made its drive clutch part of the crankshaft with the stationary sheave threaded onto the crankshaft with a splined part for the movable sheave extended out. This changed about 1974 when Yamaha came with a 30mm crankshaft stub.
Yamaha also began using twin Mikuni carburetors in 1968 that were way ahead of their time for snowmobiles. In 1969 if you had a problem with your twin carbs Yamaha even had a kit to replace the twins for a single Keihin carb. In 1969 Yamaha also added a disc brake for quicker stopping.
In addition, those ’68s had straight handlebars while the ’69s were bent in the center back toward the rider. For 1968 the sled’s fuel tanks were in back and there were straight side tunnels, while ’69 models had strengthened indentations on the tunnels sides.
The ’68s also had small round front bumpers with big hood latches holding the hood’s rear down while the ’69s had larger front bumpers with a dash-controlled hood latch. Plus the ’69s used a fiberglass belly pan extension.
Tracks? For 1968 the Yamahas were center drive with that system being used until around 1977 when Yamaha converted to internal drive. Track thicknesses also changed through the years to create better traction for aggressive riding.
For racing, in 1969 Yamaha offered a GYT racing kit that came with pipes and carburetors. This created a different look as the pipes came out the front and right side of the sled, which forced you to cut the fiberglass belly pan just to install them. Maybe three of these kits remain on sleds now and the Grundeens have one.
While many improvements were made in the early years the Grundeens say the ’68s and ’69s handled and rode better than the ’70 to ’73 models. By ’74 Yamaha had improved handling and continues advancing technology, recently introducing electronic power steering on several sleds.