I have noticed that alot of shops will not do any work on the DS because of the Rotax engine. What is the difference between a Rotax engine and another engine from Yamaha or Honda???

 

It all about the dollar. They dont have any information on it and they dont want to spend the time or money to get the info. They probably have most of the Jap manuals cuz there are so many of them out there but when it comes to an engine they will see very few of, they dont see the need to invest. They may also be concerned with parts availability.
Being a service manager for many years I can understand their decision but it sure doesn't help the shops image.

 

One of the things shops fear is they automatically think of the Rotary Valve desighn that Rotax is famous for in the Ski-Doo snomobiles. Otherwise known as R.A.V.E.. It is an awesome desighn and I wish they would incorporate it into the quad scene. Rotary valves can acheive unbeleivable RPM's.

 

But what is the major differences in another post about a CT 105mm piston someone was talking about how only a few people bore the Rotax out cause it is coated with Nikasil or something like that. What does Nikasil do? Can you do with out it?

 

In your basic Jap quad motor they use a steel cylinder liner for the piston rings to ride on/against, the rotax (and also the new preditor motor) don't have a steel liner in the cylinder, their cylinders are all aluminum, the aluminum in the bore is nikasiled so that it can take the wear and tear of the piston/rings, you must re nikasil the cylinder if you bore it out, the aluminum without it will not last, of course if you bore the stock cylinder you also have other issues to consider such as cylinder wall thickness. the rotax also has dual overhead cams which act directly on the valves, while most (if not all) the jap quad motors have a single overhead cam with rocker arms to actuate the valves

 

The obvious benefits of not using the sleeve, is weight savings, as well as better heat dissipation.

 

Deffinitely the heat dissipation is the major plus. The Z-400 is also nikasil, as is the Predator. Its the wave of the future, as compression ratios continue to climb and push the limits of heat tolerance in conventional steel sleeves. Some people will say the aluminum cylinders run hotter, because the coolant gets hotter in some cases, but fact is the coolant is hotter because it removed that heat from the cylinder, and combustion temps as a result can be lower.

 

High tower is correct you get longer life more consistan cylinder temps pluss lighter weight, Nikasil has been aroung for a long time dirt bike engines have been using it the tecate 3 wheeler used a crome plating for the same thing.
Also steel and aloy expand at different rates so a thin sleave which is nessry to build a compact big bore motor can distorte. Nikasil has also been applied (it is where it was first used) to valve and seat faces, when lead was banned something was needed to protect these areas from heat and the lack of lubrication. It is super hard and very durable and resist flaking off like crome.

 

Actually RAVE is not the rotary valve, it is the exhaust valve. Here is from Ski-Doo:

RAVE™(Rotax Adjustable Variable Exhaust) — The RAVE valve provides optimal throttle response and increased power in the low- and mid-RPM ranges, increased fuel economy and improved emissions quality by changing the size of the cylinder’s exhaust ports. At low and mid-range RPM, the valve is closed. But when the engine reaches a higher RPM, the valve opens, creating a larger exhaust port for freer flowing gases and increased power capacity.
Benefit: Basically enables motor to be two-engines-in-one – one tuned for peak power, another for satisfying torque.

 

I stand corrected thank you