SX/SXi/SXi Pro Making the most of it 750sx

[hornedogg79]

Wasn't really looking for a 750sx, but I couldn't pass on the deal. It sat in my yard for a year as I worked on other people's skis and slowly collected parts. Pump was locked up, midshaft shot, top end scorched, botched nose repair, cracked fuel door. Looked pretty rough and I doubted if I would ever build it.

I really wanted to build a 550/750 conversion ski so I decided to rebuild the motor, pump, and midshaft. I made a list of everything else I needed and realized you can buy a round nose sj for less $. X2 driveshafts are $400 these days. Motor kit, pump kit, ride plate..etc.. adds up quick! I put that idea on the shelf and started working on the 750 hull. First thing I did was fill the driveshaft void and smooth the intake with a piece of PVC and thickened epoxy.


I bought new cables and a Yamaha start/stop because I hate the kawi ones. I needed a pipe and scored one from an SXR that I installed a new wax pipe on. This meant I needed a different waterbox somewhere up front. I cut up a waveblaster 2 box and welded it back together so it fit in the old oil tank location.

The nose got reinforced and the cracked fuel door filled in. I had this internal fill for a Kawasaki tank so it worked out. Got it all together and fired it up in September and pushed it to the side again. Mostly complete but missing the nose bumper.


Here's where it starts to get fun. I watched a video from Sold Out Co. where they went to hang out with Chris the fish Fischetti. Dude still has a passion for tweaking his skis after all these years. Making changes then going and trying it out. Thinking outside the box and looking to make improvements. That's what I enjoy too. It got me to thinking... What would it take to make this 750sx ride better?

I traded a mat kit for some tom21 tubbies and had a friend print some hull extensions I found on eBay.
New hydro turf with 18mm underpad and rear kicker wedge.



Spoiler alert: it still sucked

 

[hornedogg79]

I have been out on it 3 times making small changes like washers between hull and ride plate. Dried out the SXR exhaust. The ebox was the only thing I hadn't touched on this ski. It worked so I didn't bother. 2nd ride I lost spark. Opened the box to find a swollen SBT cdi and msd coil. I replace those with an OEM 3738 cdi and Kawasaki coil with new Tons copper core 7mm wires and msd crimp on ends. Ski starts and runs great now.


Ski feels ok in a turn but pretty unstable in a straight line. Typical 750 behavior. The sxi pro had rear sponsons which were basically rail extensions. The tubbies are placed low and you can feel them grabbing with the slightest lean. They definitely help this hull initiate a turn but it's almost too aggressive and take some getting used to. I've found getting my weight further back helps so I may end up needing a longer pole. Lots of spray to the face in a turn too.

 

[hornedogg79]

I've modified the bond rails on 3 different fx1s and it's hands down my favorite upgrade for that hull. Why not try it on a 750sx? Gonna make that pointy nose a little more round while I'm at it.

 

[Myself]

The 750's are sort of like the Studebaker of jet skis, sometimes one gets fixed up LOL!!

 

[hornedogg79]

Got it flipped over and pulled the foam and tape out. Now I'm laying glass on the bottom side. Top side carbon was about a 1/16". I'll shoot for an 1/8" of glass and another 16th of carbon cap it off. Tubbies used to stick out farther than my rails. Not anymore.
Compared to a modern race hull, these chines are puny. I'm thinking about getting a rod of fiberglass rebar to attach and blend in. The keel currently sits 1/2" deeper than the chines and I think that's why it's so sketchy on plane. Too much of the hull is out of the water.

 

[fastgtfairlane]

those hull extenstions look good!

 

[WFO Speedracer]

I always liked the way those hulls looked but not the way they rode , the worst part to me was the porpoising they are notorious for that ., I am sure the hull extensions helped with that greatly .

 

[hornedogg79]

those hull extenstions look good!

Yes and they seem really strong. Petg cf is impressive. Excellent job sir.

I always liked the way those hulls looked but not the way they rode , the worst part to me was the porpoising they are notorious for that ., I am sure the hull extensions helped with that greatly.

Same. Very sleek design. I've worked on a ton of them and the test rides are always short. Watching old videos from the mid 90s to early 2000s makes you wonder what their secrets were. The extensions pretty much eliminated the porpoise. I didn't even notice it before I put washers on the back of the ride plate.

 

[WFO Speedracer]

Kawasakis were very popular here back in the late 80's and early 90's , hell that's all there was and the dealership I worked at really pushed them hard , that's when I got into skis and those older skis like this are what I cut my teeth on.

Then in 88 the Seadoos came out , in 89 Yamaha came out with the WR500 , then Po;aris , Artic cat , Mastercraft and a host of American companies trying to break into the market , the Kawasaki dealership here took on Polaris, then it changed hands , he didn't push the watercraft at all the way the previous owner did ,he was a motorcycle guy and a lying scumbag and I left there for greener pastures , but that is another story , he totally lost out on the watercraft marketshare , to this day they barely sell any watercraft here, It's pretty much all Seadoos and Yamahas now with just an occasional Kawis in the mix.

 

[kevbo]

Got it flipped over and pulled the foam and tape out. Now I'm laying glass on the bottom side. Top side carbon was about a 1/16". I'll shoot for an 1/8" of glass and another 16th of carbon cap it off. Tubbies used to stick out farther than my rails. Not anymore.
Compared to a modern race hull, these chines are puny. I'm thinking about getting a rod of fiberglass rebar to attach and blend in. The keel currently sits 1/2" deeper than the chines and I think that's why it's so sketchy on plane. Too much of the hull is out of the water.
View attachment 459905

The old 750 has a lot of dead rise. It was designed to turn on edge at higher speeds than the 550 could. It didn’t last long because race courses got bigger and slalom went away. It was a lot easier for riders to run a Superjet wide open the whole race than it is a 750. If you want to make it easier to ride fast, try taping some flat strips 3/4”x1/8” to the bottom edge. Build them up until it stops getting so tipsy at speed. Then make a more permanent set. Getting tubbies working right is an art. I don’t race so for me they are more of a PITA than anything I can really use.

 

[hornedogg79]

Giving off GP ski vibes haha. I need to ride it before I change anything else. Freezing today but tomorrow looks promising.