Top End Decisions

[RiverBandit]

You don't see many 650sx in that condition. I'd keep it as clean and factory as possible. The most molded 650sx in the world, isn't as fun as a stock superjet. In mine and many other opinion anyways.

A better option for a guy looking to get into freestyle or a rec ski. Would be to buy a superjet this winter in low season. And sell that cherry 650sx next yr in peak season for a break even deal. It's absolutely possible.

Either way. That's a clean sweet ski and I wouldn't go throwing a ton of money at it. I'd wager a good amount of money it won't need any hard parts for years to come.

I remember when Yamaha first released the "SuperJet" ... we all thought "How cute"

Not taking anything away from today's freestyle riders. This is what I remember -->

If I'm honest the older skis are comparable to riding a broom. I love the idea of today's machines with so much horsepower they flip over when you blip the throttle... but try manhandling one of these old-school 550 shards and get it to do what you want in chop. It wasn't easy, but it was A LOT of fun!

That aside ... I think I want a new "Freestyle" SuperJet ... they're cute too

 

[RiverBandit]

650's are damned hard to kill at least in stock form , I had an engine in my ski I built from a bunch parts laying around the shop, 650 crank in small pin 750 cases, modded stock pipe TR racing head , a 44 carb and adaptor on a stock 750 intake with some voodo magic to make it all work together , clearances I have no idea , I didn't check them, I beat the piss out of it for a few seasons then I had a freeride coming up and decided to freshen it up , I took it to my cylinder guy with a set of .050 pistons , he said it was so worn that it wouldn't clear at .50 o/s I didn't have time to get more pistons in and get it bored before the ride so I put new std rings in it and put it back together, I think I got two more seasons out of it before I built a ported engine and replaced it, it still ran just fine.

This is the insanity I remember ... re-ringing and reusing gaskets with a little copper spray. I can remember pulling a head from one ski and popping it on another and kept right on riding. Precision did not have meaning for me until later in life. This is uncharted territory ... I remember how these machines behaved when they were new. Almost half a century later I may as well be using a hammer to tune this thing. Still can't believe it runs!

 

[WFO Speedracer]

Back in 91 when I started at the Seadoo dealer the 587's were seizing top ends left and right, these guys were not even boring cylinders, they were sending them back to Seadoo and having new liners put it with new std size pistons , so the clearance always stated the same, somewhere between .002 and .0025 piston to wall, I said this is BS and started having the cylinders bored using .004 and we went to .005 one set just to see, the ones at .005 were a little rattly so I went back to .004 and thats the spec I stayed at, most of the seizing problems disappeared.

I pretty much just used 650SX piston to wall clearances.

 

[TheBuzzard]

It's got an aftermarket tail section on that stock pipe that increases chamber volume and adds torque. And if you knew what to look for, you might have seen the gas spraying back out the carb top when those bad reeds were stuffing the crank case pressure back thru the carb

 

[RiverBandit]

It's got an aftermarket tail section on that stock pipe that increases chamber volume and adds torque. And if you knew what to look for, you might have seen the gas spraying back out the carb top when those bad reeds were stuffing the crank case pressure back thru the carb

"If you knew what you were looking at" ... So, like you're saying I didn't know what I was looking at, right? I get it ... you must be highly trained and smart

Yeah so I went to look at the ski on a floating dock ... the flame arrestor was essentially glued to the carb. It was "wet" and the smell of fuel was prevalent. One of the first things I said was "This thing probably needs reeds" ... If I was a smart guy I probably would have known that before I ever pulled the cover off the hull.

 

[kevbo]

If I had that ski , I would get a 750, a pipe, and prop. Repair everything else, especially the loose pole, and it would be a very fun ski. It would cost an extra $3000 or more to do it right. I have done this to all my old Kawasakis and they're actually enjoyable to ride now.

 

[Pro-pulsion]

You might find some info on this old build thread useful, hope it helps...

Completed 650SX Build - From 50Hp to 60+ | X-H2o