Henn Linth’s #59: Kawasaki Jet Ski SX-R
The trickiest SX-R
Henn Linth’s special SX-R tops 66mph on pump gas with a cranking compression of almost 200psi and features GP technology. Is it unique or what?
Test rider: Vasilis Moraitis
I have tested many Factory, Semi-Factory and highly tuned stand up Ski’s since 2002 and happy to say that I still remember how each one of them performed. I have seen many different recipes illustrated by different tuners but to be honest apart from the two particular SX-R’s (R&D’s 2006 SX-R prepared for MacClugage and 2008’s SX-R prepared for Jean Baptiste Botti by Pascal Barriac) I have not seen lately something extraordinarily tricky. Whoever wanted more speed has gone for a four-stroke as far as I know from the well known and respected tuners and athletes in Europe and in the USA. The very first day in Havasu I was introduced to Henn Linth, a tuner from Estonia and close friend of Markus Erlach. This guy is completely unknown in the Jet Ski Racing world but he has a great knowledge and experience on building race engines from the GP125 and GP250 scene where he was working since he was very young. Lately he has been working on his SX-R and has applied some of the GP features to the simple two-stroke technology that Kawasaki uses on its two-cylinder engine.
Henn started working on this engine right from the bottom, which is no other than the crankcase. According to Henn, when temperature rises crankcases expand and bearings turn looser. This is a point were the engine’s power is faded. Therefore, he focused on keeping the temperature of those SX-R cases at a low level by making them water-cooled. The bottom case is made of billet aluminum and is fed by water through the pump. The Kawasaki crank is good enough for the stock engine but when you apply higher forces to it you need better bearings. Henn relies on Rotax bearings and insists that those are very high quality bearings.
The water leaves the crankcase and finds its way to the rear cylinder through a half inch fitting. The cylinder itself is ported by Henn using the “trial and error” method. According to Henn most books and mathematic equations are good up to a certain point, and then you realize that if you do not experiment you are not going to have the optimum result. The ported cylinder is topped with a girdle billet aluminum cylinder head that is made by Henn himself. You would simply ask “Why he did not buy one off the shelf?” Because his cylinder head features offset dams that are closer to the induction side. It is the GP technology that enables the mixture to burn more efficiently and then escape faster from the exhaust port. Bear in mind that Kawasaki applied the same technology this year to the high tech ZX-10R!
Last but not least is the issue with the twin pipes that this engine is equipped with. Henn stated that those pipes are not working properly and the truths behind these issues are the length and the diameter of the tubes that connect the expansion chambers with the waterbox. We were informed in the past from another person who worked a lot with this set of pipes on the dyno that he had similar issues. Therefore, Henn started evaluating those dimensions and then built his on tubes out of carbon/Kevlar in order to achieve the appropriate diameter and angles on each tube. The result was simply outstanding and the pipes matched with the rest of the tuning spec.
Henn has also fabricated some of the body parts. Rail caps, dashboard, nose piece and ride plate are made of Kevlar. Apparently the ride plate is an actual copy of Craftsman’s Movement Takenoshita replica however Henn added some holes at the side and on the rear end in order to enhance grip at high speeds. He also uses a 3DR hood in order to bring more fresh air to the engine compartment.
The moment of truth
I rode Linth’s SX-R a few minutes after I finished the test ride of Markus Erlach’s big bore SX-R therefore, I actually had a good reference to compare the two projects which had only two things in common: the use of pump gas and the ride plate. Additionally, the two race crafts shared the same steering system set up and almost the same handling aftermarket parts. In other words I was familiar with the RRP MX type bars and the short turn plate as well as the peculiar ride plate.
In terms of power delivery Linth’s SX-R felt a little bit empty at very low rpm. In other words, the engine’s response was not so accurate “live” from idle to mid range. Almost before mid range the engine was pulling hard and kept pulling till the rev limit. This was a nice feeling and when I was riding on the upper rev range I could feel that I was moving seriously fast. This was a good set up for someone, like Botti, who can hold on to the throttle for most of the time.
The handling was agile, accurate and the hull had the tendency to lean over in a more progressive manner when approaching the buoy. This kind of performance was enhanced by the concave shape of the ride plate. At the same time the pointed sides of the ride plates act like fins that result on a better hook up of the rear end. Therefore, this attitude really helps the rider who decelerates late and comes early back on the gas. Meaning, you can load the pump without fearing of high siding. On Havasu’s water, stability was not an issue on Linth’s SX-R even when I was reaching its top speed, though it had a different feeling from other set ups I had tested in the past. On long sweepers the handling was good and there was absolute no sign of rear end sliding. The big difference in terms of stability I could feel were on the exit from the buoy. This particular SX-R had the tendency to return from its lean over angle to its flat position while I was exiting the buoy. This feeling was very strong and in the beginning I could not realize what was producing it. Afterwards I found out that Linth’s front sponsons are filled with inox for this particular reason.
Top speed was not in the upper 60’s but it was enough for rider that wants to win Expert or Masters class or even to place them in a very good overall place in Pro Ski. According to Linth, this set up results in a top speed of 66mph, which is a remarkable achievement since the engine operates on pump gas. Most SX-R’s of this level work on MS109 or other race gas.
If I have to make a quick comparison between Markus’s and Linths’s SX-R, I suppose that Markus’s feels easier to ride since it has a more full power band while Linth’s is a race oriented Ski for the experience rider. Having seen and ridden many highly tuned SX-R’s I would say that Henn Linth’s project is a very interesting approach and at last we see someone new in the Jet Ski Racing scene who is putting together new ideas. Linth has already tested many of his aftermarket parts but all of them were mostly made for LIX Team riders, friends and co-racers (Markus Lutsokert and Andres Kalmer) but he plans to release some of these in the market in the near future as soon as he will be able to have his own CNC machine in his workshop. It will be interesting to see this guy entering the personal watercraft business.
Henn Linth’s #59: Kawasaki Jet Ski 800 SX-R
Kawasaki OEÌ upper crankcase
OEM bottom crankcase with “LIX” billet aluminium water-cooled jacket
Stock crankshaft modified with Rotax bearings & aftermarket rods
Bore x stroke: 78 x 84.5mm
Kawasaki stock cylinder
“LIX” Billet aluminium cylinder head, with offset dams of 25cc
Henn Linth’s cylinder porting
Wiseco 84,5mm pistons & rings
Cranking compression: almost 200psi
Twin Dry Pipe Exhaust System heavily modified by Henn Linth
No base gasket just silicon
VForce 2 reed cage and reeds
TBM aluminium reed spacers
Novi XR 48mm carburettors, 1st generation
Hot Products air filters
Cold Fusion billet dual fuel pick up
Modified water box for better midrange
Cooling lines in: 2 in, one in exhaust and one on crankcase
Cooling lines out: 4 from the head out
Fuel: pump gas
Lubricant: MOTUL 800 off-road
Igni Pro programmable ignition with Superstock mapping made by Markus Erlach
Modified Stock flywheel (1100 g)
NGK BR9ES Spark Plugs
Pump and driveline
Skat-Trak 142mm, 12 vain Magnum Pumpw/30mm Setback
Skat-Trak(13/23) three blade impeller
Skat-Trak aluminium pump shoe
Skat-Trak extended drive shaft
Skat-Trak long drop nozzle (cut by 2cm) system
Reduction nozzle: 82mm
Steering nozzle: 85mm
Nenn Linth's Kevlar ride plate
Skat-Trak intake grate
Hull and Handling components
Kawasaki stock hull
Henn Linth’s made special front sponsons
3DR high flow hood
Henn Linth's Kevlar nose piece
TBM gas cap
Henn Linth's Kevlar dash board
Henn Linth's Kevlar side rails
Jettrim mats with lifters
RRP twin duct pole bracket
Billet aluminium hood brackets
RRP carbon fiber chin pad
RRP MX type handlebar
RRP short turn plate
Skat-Trak heavy duty steering cable
UMI Racing trim lever
Aftermarket trigger throttle lever
Skat Trak trim cable
Horse power: N.A.
Top speed: 66mph