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American Snowmobiler named the Yamaha Vmax-4 "Sled of the Year for 1992." It was as subtle as a 400-lb. fullback pounding through a Pop Warner football league defensive line.
The Vmax-4 was broad, giving room to an inline 4-cylinder 2-stroke that sat low in the engine bay. The styled hood had a low snout with twin flared nostrils and abundant air inlets to keep its 743cc quad cool and happy. It was an example of what the Yamaha faithful knew would come - someday!
The Vmax-4 was the long-awaited successor to the SRX and the 540cc Vmax power sleds. It was an engineering coup that would lead a new line of Yamaha Vmax models and carry Yamaha from the end of its 2-stroke era to the beginning of the 4-stroke era. The Vmax-4 was the only production trail sled with a 4-cylinder engine until the arrival of the RX-1 4-stroke.
The liquid-cooled 743cc motor had a bore and stroke of 63mm by 59.6mm. It was fed by four flat-slide TM38 Mikuni carbs, which drew fuel from two Mikuni fuel pumps. Rack-mounted carbs helped make the throttle pull light and consistent. Clutch engagement was set at 3,500 rpm with full shift at 8,300 rpm. The Vmax-4 was strong and built power like a turbine. The horses just kept pulling… and that was the trail version!
For the 1991-92 racing season, the Vmax-4 fell to the magic of Tim Bender and Bender Racing. It would be the fastest sled on the Formula III circuit. While the Yamaha/Bender Vmax-4 combination didn't win the "big" race at Eagle River's Formula III World Championships in 1992, the sled was so fast and reliable that it was essentially outlawed when the displacement rules were changed to limit F-III sleds to a maximum of 600cc.
With the Vmax-4, Yamaha engineering went its own way on design. The engine used a gear reduction system to lower engine revs and let the drive clutch spin at 95% of the engine's speed. (Gear reduction is still used on select Yamaha snowmobiles - the Apex and Phazer engines.) The power take-off shaft was center driven, leaving a center space and making the Vmax-4 engine look as though it had two twins packaged together.
Yamaha suspensions also were different from the competition. The front end was the high point for the Telescopic Strut Suspension. Yamaha's use of TSS had been around since the 1980 SR-V. It was an excellent design for straight runs and became quite adept for cornering, once linkages, sway bars and shock packages were figured out. Bender Racing offered front-end kits that made the trail Vmax-4 corner like its Formula III racer.
The sled felt wide on the trail. It was extremely smooth getting you to speeds more quickly than you thought. Checking the speedometer was always a good idea just before you headed into corners. Fortunately, Yamaha equipped the Vmax-4 with a capable brake.
In later years the Vmax-4 engine enjoyed the benefits of revised port timing and a higher compression ratio. All made the later versions smoother and more powerful.
First on the snow in the winter of '91-92, the Vmax-4 remains a unique snowmobile to have in any sled collection. It was uniquely Yamaha and a tribute to the company's 40 years of engineering truly interesting snowmobiles.