1995 yamaha vmax4 800

Careful now, don't refer to the Vmax-4's new 800cc quad as a bored out 750. Okay, the new for 1995 Vmax-4 measures 791cc and it came about by increasing the bore of the 750, but this engine is much more than four re-bored cylinders.
In reality, what Yamaha learned with the old 750 inline four serves as "ground zero" for the 800. The obvious change is the bore, which increased from 63mm to 65mm while retaining the 59.6mm stroke. Not so obvious is that the entire engine assembly is virtually new from the crankcase up.
In fact, the crankcase is new. So is the crankshaft and power takeoff shaft (PTO). Because of the new crankshaft and PTO arrangement, the crankcase had to be redesigned. From the outside, you can't tell that the new PTO shaft has dual driving gears, but when you compare the 750's crankcase with the new one, you'll note that the area allowed for the center PTO drive is bigger. This creates room for the extra gears and more lubricant. In some ways, what you have here are two twins feeding into a central output shaft.
Yamaha has worked hard to handle the additional 12 horsepower of the bigger motor and at reducing harmonic vibrations in the quad. From the dual individual gears on each side of the crankshaft right down to isolation engine mounts, Yamaha engineers have made every attempt to reduce engine and drivetrain vibrations. Overall the new 800 is a smoother running motor than the older 750. With the 800's horsepower expected to be more than 150 versus the 140-ish power output of the 750, smooth running is mandatory for prolonged drivetrain life.
As noted the new quad gains power from the overbore but gains also come from the triple exhaust port design and a larger reed valve set-up on the induction side. The exhaust system, a dual set-up of two pipes into one, is new and dyno-designed expressly for the 800.
Yamaha has revamped the digital ignition timing to match the 800's characteristics. Built into the ignition circuits is a 10,000 RPM rev limiter to protect the motor. For example, if a drivebelt blew under full throttle on a high speed run, the engine would cut out once it reached 10,000 revs. Yamaha also has a throttle control on its four 33mm flatslide Mikuni carb set-up to cut the engine in case ice froze the throttle line open.
To keep this new engine cool, Yamaha has a set of snow-collecting extrusions mounted at the rear of the tunnel. The flow of the coolant has been revised to provide a directed path versus the flood style system used previously. What happens now is simple. Just as with a car radiator, the coolant is directed through chambers in a controlled path to create better and larger surface cooling. Yamaha discovered that this simple procedure was so efficient that the front heat exchanger could be eliminated, saving weight. This controlled cooling system is standard on all Vmax models for '95.
Frankly, power really hasn't been the problem with Yamaha snowmobiles. Getting the largest percent of that power to the track has been. In an attempt to get max power to the track, Yamaha has totally redone its clutching system to make it more efficient.
Since Yamaha builds its own clutches, it can set higher internal standards for manufacturing tolerances which should result in reductions in binding and friction. The primary clutch has a new sheave angle; increased from 13 to 13.5 degrees for improvement in acceleration. Addition of low-friction bushings are said to improve overall performance as well.
The primary clutch enjoys recalibrated weights, rollers, rivets and springs. Two fixed bearings of a more friction-free material replace the former spherical bearings used on the previous version of the YXRC drive clutch.
Major changes were made in the secondary or driven clutch. This is new to Yamaha but will look slightly familiar to Cat fans as the new Yamaha driven is a reverse torque cam design. Belt replacement will be easy as you just push in the cam to relieve belt pressure and free the drive belt.
The new secondary has a wider bearing area to reduce friction and binding. The design is an "open" style for better cooling. And the new secondary clutch features a revised sheave angle from 14 to 14.5 degrees to improve belt grip, thus efficiency.
Yamaha has worked hard to revise the clutch system and feels that this attempt will pay off in improvements in both upshifts and downshifts. The clutches are designed to grab the belt better which will definitely aid backshifting characteristics.
Under the hood isn't the only place Yamaha made improvements in its top of the line snowmobile. Check out the wider ski stance on the short track model. It now measures 40 inches. The long track Vmax-4 ST version with the "mountain master" high profile track retains the 38.5 inch ski stance for better agility in deep snow. The deep lug profile of the longer 15x136 inch track measures 1-1/8 inches in height. A word of caution, though, this track is designed for deep snow use. You may find it unsuitable for normal groomed trail riding. In deep snow this track has the same effect as tire chains. It grips.
Overall, the Vmax 800 retains the basic chassis configuration as the previous 750 version. You'll find the multi-adjustable Telescopic Strut Suspension with 6.8 inches of travel up front. At the rear is an upgraded, but not new, Pro-Action Link suspension complete with nitrogen gas shocks and adjustable preload capability to control the 8.5 inches of rear travel. We have no complaints with either set-up since the Vmax-4 also has a quick-responding swaybar to transfer ski pressure action from ski to ski and the Pro-Action Link is a proven design.
One thing we like about Yamaha snowmobiles is the attention to detail that they seem to have received. You can adjust the throttle controls and handlebar to readily suit your personal riding style. Fit and finish is the best of any manufacturer.
However, one thing we figure that you'll need to get used to is the self-adjusting mechanical disc brake. The brake comes with a large, externally mounted 220mm rotor that is mounted in a flow of constant circulating cool air.
The brake works fine, no problem there. But, since it is self-recovering, when you use up the brake and it needs to readjust itself, you may find that you once grab a handful of brake lever and the very next time you reach for a handful the brake action is short and response is quick. With a mechanical system where you are relying on mechanical advantage and not hydraulic assistance, there is plenty of forgiveness available and you won't find yourself going through the windshield.
That's an asset as the Vmax-4 comes with a new blacked out racy windshield. You'll also find thicker, longer wearing plastic ski skins on the aluminum skis; a redesigned footrest for better toehold and overall increased ride stability; a more convenient plug holder located under the fairing; a large 10-gallon fuel tank; halogen headlamp; and full instrumentation.
And, new for this year, is Yamaha's infinitely adjustable hand and thumb warmers. These warmers work much better than the previous year's warmers. Plus, adding a rheostat control allows you total control of the heat range. That will be a plus for Yamaha riders.
Overall, the Vmax-4 with its 800cc quad is a plus for Yamaha fans. There's more power from start to stop due to many and varied engine improvements. The clutching changes should eliminate any complaints Yamaha owners held. Wisely, the Vmax-4 retains consistent handling available from proven systems like the TSS front and Pro-Action Link rear suspensions.
So, with more of what performance buyers demand - power, the Vmax-4 should be a winner. We didn't find any glaring faults. Like its 750cc predecessor, the 800cc version is very well-mannered for sports performance touring. And, now, when you hit that long straight-away, full throttle on, you'll have even more performance. Smooth, four cylinder