650/X-2 My $200 Craigslist Find (I am new )

[ifuonlyknew]

So, at the begining of last summer a few of my friends picked up some stand ups. I had just got out of the Air Force, and was going to be moving back to Utah at the end of the summer. I really wanted to get a stand up and ride with them, as I had riden standups growing up, but I knew it wasn't in the cards. Fast forward to a week ago, I find this little gem on Craigslist for $200.



It had a blown up top end, but for $200 I figured if it had the right parts, I would grab it, and get it running for next summer. At this point let me state that I know the 650SX's are not known to be the greatest ski's, but my intentions are to get this going, ride/tune it next summer, and to get a SN at the end of next summer and keep this as my loaner. That said, on to my plan.

So I drive an hour on a hunch that this ski would have the parts I want/need to build it the way I want. The lady selling it was actually selling it for her father. He owns a boat shop, and took it on a trade a long time ago. One of his employees was gonna get it going, but back then without the internet at his fingertips, he gave up. The guy is checking to see if he still has all the parts, if so it is gonna save me some $, and really help me out. So needless to say she really had no clue what was going on, other than it didn't run. So I pull up and pop the hood, just as I expected, no head, no jug, one piston. On to the good, I was hoping that it would have all of the bolt ons, and it does, and then some. It has a PJS Impeller, Ride Plate, and Top Loader Grate. It has a Jetcraft Engineering Waterbox, an aftermarket pipe that I can't identify due to the fact half of the expansion chamber is missing (removed with top end) I have no Idea what the pipe is, and when I was taking pics I forgot to get one of the exhaust. I will get a pic later. I was really hoping the ski would have a lightened flywheel, and as soon as I popped the hood I knew it did, plus a little more. The ski has a full PJS total loss ignition! I don't know if these ignitions are reliable, if not somebody please say something now. The hull itself was in immaculant condition, no cracks around the handle pole or anywhere else, but as you can see from the pic, the turf and paint were destroyed by years of sun. The last year it was registered was 97!

So, on to my build plans. Since I am going to need to buy a jug and head, I figured I would do a 750 top end swap. I am gonna have the crank checked (it feels good and free, and the rods look good, but I just want to be safe), and install new crank seals. I have a set of Wiseco 81.5mm pistons, that are for a 650 bottom end. I understand that there is going to have to be some machine work done to mate the top and bottom ends, but it's cool. I am planning to replace the studs on the intake side, and run spacers on both sides of the reeds to help the bottom end deal with the demands of a 750 top end. I know I am going to need a decent carb to keep up with all of this so here is my next question. What carb do I have here, and will it work well for what I have planned? If not what would you experts suggest?



The first thing I wanted to do is clean out the engine compartment. As you can see from the pics it was really bad. So I stripped the ski down, and took the pressure washer to it. Here is a couple before pics. Still need some after pics.



The plan is to have the whole ski re-painted too. I want to do primer grey, and black turf. I want to get a quick steer plate too.

Well thats it for my first post, I have a long winter ahead so I'm sure I will be on here a bunch more. I am open to any help or suggestions from you guys. I was gonna post this on that other forum too, because I know this forum is more about freestyle and I figured I would get more attention from people with experiance doing similar builds there, but I think most of you frequent both forums, so it is good I guess. So I had actually registered there at the same time as here, but they deleted my account because "I did not meet some requirement". I emailed the admin that deleted my account, but of course they are hiding behind their keyboard, and have yet to respond to my not so friendly, inquizitive email reguarding the deletion of my account. What ever.

Thanks in advance,
Ifuonlyknew

 

[SUPERJET-113]

Welcome to the X!
Thats a good deal with all the parts that it came with! People will pay up the azz for PJS stuff on Ebay. You could probably get more than your money back just on that TL system.

The carb looks like a Keihin 38. The earlier year 650sx came with 28 Keihins, but the fuel pumps were remote. Your has the pump on the side of the carb. You can measure the bottom throat of the carb to be sure.
With your new plans that 38mm will work but I would try to find a keihin 42mm carb, because you can still use the existing manifold. You just have to hog out the throat area to 42mm(to match carb throat). Or you can get anew intake manifold that will hold a Mikuni 44 carb also, but that will cost you more $$.

 

[B3IS]

Welcome cool story and look forward to more posts about this adventure.

 

[AtomicPunk]

I knock the 650SX pretty hard, but it is better than no ski.

Welcome to the X.




ps, I hear there is a guy on here that can turn that into Superjet (only better).

 

[Vumad]

I have several 650 cores sitting around I haven't bothered to sell yet. I am sure I have a head and cylinder you can purchase. But, Also remember that your crank is probably as wasted as the rest of the motor. It might be best to buy a complete clean 650 motor. I can't help you with that.

The following is from Group K. I myself would get a 750 motor and run your 650 electronics, or get a rebuilt 650 motor. Frankensteining something that doesn't work at all together is probably a waste of time and resources?

http://www.groupk.com/restof650k.htm

Big boring a 650 cylinder to anything near 750cc is obviously not doable. Installing the longer stroke 750 crank in the 650 cases is also not doable (won’t fit), and installing the 750 cylinder on 650 cases is a setup wrought with lots of undesirable technical compromises. Many 650 owners in the past have fitted entire 750cc engines into their 650 hulls, but the end result is questionably worth the cost and effort…here is why.

Why not go to 750 instead of staying 650?

The main reason that 650s fell from favor among pwc enthusiasts in the early 1990s was that the bigger 750s were better suited for the high speeds of professional racing. The 650s were (and continue to be) reliable, fuel efficient, fun and fast PWCs. For non-racing recreational applications, a 650SX is still a fantastic boat.

One common desire of many 650 owners is increase displacement, or upgrade to 750cc. Before upgrading your 650 to 750, there are a few important things to consider. The bore and stroke displacements are as follows:

OEM Stroke
OEM displacement
1mm over
2mm over
3mm over

650 70mm
76mm 635cc
77mm 657cc
78mm 668cc
Not available

750 74mm
80mm 743cc
81mm 760cc
82mm 779cc
83mm 795cc


Big boring a 650 cylinder to anything near 750cc is obviously not doable. Installing the longer stroke 750 crank in the 650 cases is also not doable (won’t fit), and installing the 750 cylinder on 650 cases is a setup wrought with lots of undesirable technical compromises. Many 650 owners in the past have fitted entire 750cc engines into their 650 hulls, but the end result is questionably worth the cost and effort…here is why.

The 650 crankshaft is considerably smaller and lighter than the 750 crank, allowing for very quick rpm acceleration. On top of that, the stock 650 ignition flywheel is about half the weight of the stock 750 flywheel, which further benefits the acceleration of the 650 motor. Given all this, a well prepared 650SX motor can easily match the acceleration of most 750s. The difference is that the 750 engine has the ability to drive the hull to a much higher peak-speed (close to 60mph). Unfortunately, even the best prepared 650SX hull will become “very” hard to control at speeds over 50mph….and almost impossible to control at speeds over 55mph. In our minds, if you want the speeds of a 750 motor, it’s wise to get the hull to match. However for a large number of stand-up enthusiasts, a lightweight, quick accelerating, stone-reliable 46-51mph boat is exactly what they want. From a more technical standpoint, there are also some important reliability reasons for keeping the 650cc motor.

The shorter stroke of the 650 crank subjects all the lower end bearings (and rods) to far less wear and stress than a 750 crank turning the same rpms. This is one of the reasons that 650Kawasaki lower ends have that “last forever” reputation…. Even when modified.

The head-bolt patterns of the 650 and 750 Kawasaki engines are the same. This means that the smaller bore 650 cylinder gets a much wider sealing surface between the bore diameters and the head bolts. This added surface area makes it much easier for the 650 motor to maintain a long term head gasket seal…especially when higher compression ratios are used.

There is “no” 750 that can come close to the long fuel range of a single carb 650. This is a very important quality for recreational riders interested in longer outings (and lower fuel costs).

These qualities, along with others, makes the 650SX a very practical and affordable platform that easily matches the “fun factor” of a 750 in a high-performance recreational application.

 

[Idok]

IMO....figure out what you have, it might be more worthwhile to ebay part out and cash in on the parts score........



then put that money towards a square

 

[jkemp]

for around 500 you can get a complete sbt motor, I myself have a mildly built 650 and it rips though have recently upgraded to modded rn superjet which rocks

 

[jkemp]

my 650 includes some port n polish work , BCW intake, x2 reeds, 46mm sbn carb, stock milled head, full coffman pipe with coffman waterbox, stock elestronics. AWESOME on fuel and screams and is super dependable great backup/starter ski IMO

 

[flip_flop]

What did you end up doing? Where is the KTM? Oh and you must keep that budwieser logo it adds probably 15-30 hp