Retro Rocket
Splash Magazine, March, 1995
Photos & Text By: Tom Kerker

 

"XI" BOLT-ONS FROM R&D RACING PRODUCTS

Within the past few years R&D Racing has practically taken the watercraft racing scene by storm. Just in case you didn't know, they offer a line of performance products, many of which are currently being used by World and National title champions such as, Minoru Kanamori, Christy Carlson, Nicolas Rius, Victor Sheldon, Chris Fischetti and many others.
Although racing is the ultimate proving ground for product development, owners Glenn Dickinson and Bill Chapin believe that their products should perform flawlessly, both on and off the track. This brings us to our main storyline. R&D Racing has developed a bolt-on performance kit for the popular Kawasaki 750 XI. R&D's "XI" package was created to meet the needs of the recreational enthusiast. The end results will impress you, so get comfortable and read all about it!

JUST THE FACTS

Many sit-down watercraft owners have one time or another thought to themselves, wow if I just had a little more power, that would be great! Yet, in reality you feel that messing with the factory setup will only decrease reliability. This may be true in some extreme cases, but today's watercraft are manufactured with such high standards and strong engine components, that slightly modifying your PWC usually won't hurt a thing. In fact, (most cases) the owner can really benefit from a well-designed performance package.

Now, another point to consider is that most sit-down owners have a wide variety of people sharing their units, moms and dads, children, friends, etc. With this wide range of rider styles and abilities comes the need for total reliability and safety. The bottom line here is, that nobody wants to be stranded in the middle of nowhere or left sitting on the shore with a broken-down watercraft. This sport is supposed to be fun, right? Since the key here is longevity, the performance parts you choose should be well thought out, tested and manufactured by a reputable company. R&D Racing manufactures the perfect example of a well-rounded performance package. The package we are going to test is designed to raise the overall horsepower, speed and handling of your "XI." Along with reliability, convenience is also a big factor. Since many sit-down owners enjoy the simplicity of their oil-injector system, R&D claims their "XI" package can be used with or without the injector system. The type of gasoline also must be taken into consideration. Since all Kawasaki "XI" models come with a fairly conservative compression ratio, raising the level will always improve engine performance. But, let's be realistic, for general recreation no one wants to run racing fuel in their watercraft! For racing purposes itís necessary, for recreation it's ridiculous! The rule of thumb, is to keep the compression around #175 PSI. This is the ideal/maximum ratio for 92 octane pump gas. This way gasoline will never be an inconvenience or a budget factor. It's also better for long term engine life.

FOR STARTERS

Since the release of the Kawasaki "XI" it has mechanically remained the same. It comes equipped with a twin carb, (40 mm Keihin) reed induction, 750 cc engine. Stock compression is approximately #150 cranking PSI. Engine lubrication is handled by direct manifold injection. Kawasaki uses a single stage, axial flow pump with a stainless steel, five-blade impeller. Note: For this particular test we are not going to change the impeller.

The top-speed of a stock "XI" is 46.5 to 47 mph. At full speed the rpm is about 6200. Another test that I perform is the 100-yard dash. This acceleration test starts from a standing idle, then I grab full throttle, run out 300 feet and record the time length. Our test "XI" came in at 6.53 to 6.60 seconds. Now with all the basic OEM data recorded, it was time to put the R&D Racing technicians to work. Bill Chapin and Glenn Dickinson were on hand to install their hardgoods. Now, keep in mind that the R&D package can be installed with general hand tools. The hardest part will be setting your carburetors pop-off pressure. But, don't panic, any reputable shop or person should be able to handle it for you. To begin with Chapin removed the carbs and manifold. The front covers were removed to expose the low, mid and high-speed jets, plus the needle/seat assembly. R&D recommends increasing the mid-jet from a #78, to a #82. The low and high-speed jets remained the same and are well suited for their application. Next the pop-off pressure was lowered to #17 pounds. This will ensure proper fuel delivery, at all rpm ranges. With the carbs properly set up, a pair of R&D "Reed Stuffers" were installed. These specially-molded pieces fit directly into the OEM reed cage and help increase air speed through the reed valve assembly. Having greater air velocity really improves throttle response, especially at the bottom-end range. The carburetors were reinstalled and the stock flame arrestor was eliminated. Note: For the test we used an R&D Pro-Flow Power Plenum air filter.
While the final touches were being done to the induction system, Glenn was installing an R&D timing advance plate. This trick little item advances the 750's timing from 16 degrees to a full 23 degrees. This part really helps improve low/mid-range performance. Next came the new R&D cylinder head, its specially designed combustion chamber raises the compression, about 25 pounds over stock. Perfectly suited for 92 octane pump gas. Instead of a head gasket, R&D prefers using high-temp O-Rings for sealing. Their head also has an improved water-jacket design for better waterflow and cooling capabilities.

With all the basic engine bolt-ons completed, the final engine component was the exhaust system. R&D's exhaust system works in conjunction with the stock headpipe and waterbox. Since the R&D system uses the OEM waterbox, the change in sound level is virtually undetectable. No other modifications to the exhaust system were performed. The entire R&D exhaust takes about 20 minutes to install.

The final step to the R&D Racing "XI" package was in the pump department. To help reduce cavitation in the turns and rougher water conditions, an exclusive R&D Racing "Aquavein" intake grate was installed. Their patented wing concept instantly improves pump efficiency, by keeping the pump loaded-up better. Keeping the pump loaded also improves the craft's top-speed. Since our test craft will be traveling much faster across the water, handling and stability is crucial. For added control, the stock ride plate was replaced with an R&D " speed plate." With the R&D "XI" package completed, we were ready to test it against our stock vehicle.

 

THE BIG PICTURE

Bill Chapin took the "XI" out for a quick warm-up run and a spark plug check. He then made his final adjustment to the high and low-speed needles (1 3/4 on the low and 5/8 on the high). Completely satisfied with the XI's newfound power, it was time to get some serious radar numbers. The first speed pass was incredible, the R&D "XI" broke into the mid-51ís! That was a rocksolid 4.5 mph faster than stock. Bill made a few more passes and our trusty "Stalker" radar guns revealed consistent mid to upper-51ís. Note: See sidebar for complete details.

We also recorded the increase in rpms. Our new "XI" pushed the tachometer to 6710 rpm. A 500 rpm increase over stock, means one thing, a big gain in overall horsepower! To further prove these results I performed my standard 100 yard acceleration dash. The elapsed time dropped a full second, from 6.6 to 5.5 seconds. What I like about this particular test, is that it really demonstrates the dramatic increase in bottom and mid-range power. Having greater low/mid-end power at your fingertips can be very useful, especially when you've got two people on board.

Well, now you know, when you outline a well-rounded package with all the right ingredients, the results can be very rewarding. Perhaps the best part about this package is that anyone can install the entire setup by themselves. Everything bolts into place, with no other special modifications needed. Bill Chapin made an interesting point to me. He said that many people who already own a sit-down craft or maybe even a pair of them, cannot afford to go out and purchase one of the new style big-dollar, high-performance models. So, the beauty about our performance package is that it's cost effective and the performance results are worth every penny. In addition, his/her watercraft will perform as well as some of the new expensive machines, plus it's totally reliable!

 

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