Top End Decisions

[WFO Speedracer]

Yeh. I figured

Yep That was my thinking as well, I would be way more worried about the crankshaft seals , on skis that old I just replace them , you can also red loctite the bearings when you do it.

If you are considering mods this thread is an excellent read and touches on a few of the things I already posted. earlier.

Turn your stock slow 37MPH 650SX into a respectable 47MPH SKI for around $200 - PWCToday

Here you can have a thread all to yourself, about whatever PWC build you are working on.

www.pwctoday.com

 

[RiverBandit]

Yep That was my thinking as well, I would be way more worried about the crankshaft seals , on skis that old I just replace them , you can also red loctite the bearings when you do it.

If you are considering mods this thread is an excellent read and touches on a few of the things I already posted. earlier.

Turn your stock slow 37MPH 650SX into a respectable 47MPH SKI for around $200 - PWCToday

Here you can have a thread all to yourself, about whatever PWC build you are working on.

www.pwctoday.com

Thanks again! Working on my want-want parts list.

I reached out to the previous owner who was not able to give me much information on the history of the carb upgrade. It's a Mikuni SBN 44 -- carb and appropriate intake. I'm guessing this carb was not jetted for an OE 650sx. Any input on where I should start with jetting in the southeast at about 1000 feet ASL? Idles like mud -- loads up and made my eyes water. Mid-range has a big fat boooooooooog ... Once it gets moving it cleans up. I suspect it was run lean at the top ... high-speed adjustment was 3/4 out.

 

[WFO Speedracer]

2.0 needle and seat, 80 gram popoff spring, 140-145 main jet 120 pilot jet should get you damn close.

 

[Sparkplug]

I wanna know the logic in the previous posts that thought a top end wore down to 90 psi. And ran. Like what engine experience does a person have, where they would think it ran at 90 psi???

Is suggesting a rebuild because of time? What is the logic behind it? Explain how a engine would wear from 145. To say even 120. And then with that less power, wear down to 90. How long would that take. It's like theory or experience goes out the window. No one who actually thought about the statment 90 even psi, could logically come to the conclusion that the engine WORE DOWN TO THAT, with any sort of real worl d experience combined with theory.

It's like a bunch of witch doctors throwing their sorcery at stuff I swear

 

[WFO Speedracer]

I wanna know the logic in the previous posts that thought a top end wore down to 90 psi. And ran. Like what engine experience does a person have, where they would think it ran at 90 psi???

Is suggesting a rebuild because of time? What is the logic behind it? Explain how a engine would wear from 145. To say even 120. And then with that less power, wear down to 90. How long would that take. It's like theory or experience goes out the window. No one who actually thought about the statment 90 even psi, could logically come to the conclusion that the engine WORE DOWN TO THAT, with any sort of real worl d experience combined with theory.

It's like a bunch of witch doctors throwing their sorcery at stuff I swear

I had similar thoughts but then I realized that these are the same guys that recommend everyone that has a fuel related issue rebuild their carbs with OEM mikuni carb kits knowing full well carb kits don't come with needle and seats .

There is perceived knowledge, which means you read it somewhere and took it as gospel and there is actual knowledge which is gained by work experience , they are not the same.

 

[Sparkplug]

Yeah. Learning from dad. Who learned from his grandpa. Who learned in the farm in the Great depression. Breeds ignorance. And a mentality that they know better than those who have true experience. I'm nowhere near God's gift to mechanics. But I apply logic to everything I do. And it seems to work great for me.

You wouldn't believe how many people have came to buy skis from me. Brought a pos harbor freight gauge. Read 90 psi. And the proceeded to tell me the ski was blown up. When I literally just bounced it off the Rev limiter in front of them. And rode it a tank of fuel at 45mph.

Any real experienced mechanic knows a compression gauge is only a basic tool. It's not definitive of engine health at all. Whatsoever.

 

[RiverBandit]

I wanna know the logic in the previous posts that thought a top end wore down to 90 psi. And ran. Like what engine experience does a person have, where they would think it ran at 90 psi???

Is suggesting a rebuild because of time? What is the logic behind it? Explain how a engine would wear from 145. To say even 120. And then with that less power, wear down to 90. How long would that take. It's like theory or experience goes out the window. No one who actually thought about the statment 90 even psi, could logically come to the conclusion that the engine WORE DOWN TO THAT, with any sort of real worl d experience combined with theory.

It's like a bunch of witch doctors throwing their sorcery at stuff I swear

I questioned how this thing could run with 90psi and thought "Well what the hell do I know?" ... it's been 25+ years since I changed the spark plugs in one of these. I borrowed the gauge from a "mechanic" who told me the gauge was accurate.

It ran like poop, was very hard to start, and had poor performance ... 37 years sitting on a dock and never been rebuilt - per the previous owner "I never touched the engine, reeds, nothing" ... I expected this engine to need an overhaul, but apparently that's not the case.... I'm thankful someone to point out an error

Project underway ...

 

[WFO Speedracer]

Yes with those reeds in that condition no doubt it ran like poop.

 

[mn_reeds]

I'm assuming the rebuild comments were in reference to my earlier post. There is no witchcraft or sorcery needed to know that a 37 year old unmaintained engine is going to need some work. In a less direct fashion I could have said tear down and inspection at some point in the future.

I chose not to debate the compression numbers because they were even and since the ski ran it was likely a bad gauge. OP did mention several running issues with the ski and possibility of rebuilding the carb. At that point I suggested at least a leak down so that he could tune the carb without chasing his tail due to an air leak. Discovery of an air leak at that time could also help avoid catastrophic damage.

Based on the last pics the good news is that when they put on the SBN they swapped the stainless reeds to fiber. It's also got the original crankcase drain so would recommend deleting that while you go through it.

 

[RiverBandit]

I'm assuming the rebuild comments were in reference to my earlier post. There is no witchcraft or sorcery needed to know that a 37 year old unmaintained engine is going to need some work. In a less direct fashion I could have said tear down and inspection at some point in the future.

I chose not to debate the compression numbers because they were even and since the ski ran it was likely a bad gauge. OP did mention several running issues with the ski and possibility of rebuilding the carb. At that point I suggested at least a leak down so that he could tune the carb without chasing his tail due to an air leak. Discovery of an air leak at that time could also help avoid catastrophic damage.

Based on the last pics the good news is that when they put on the SBN they swapped the stainless reeds to fiber. It's also got the original crankcase drain so would recommend deleting that while you go through it.

My head was in an airplane engine... those A&P guys take everything apart, inspect, measure, replace what's needed, and put it back together. I think these forums are great providing you verify information ... I don't take anything at face value. I do enjoy having multiple opinions to consider. The right answer is always out there ... the trick is being able to identify the correct information. I still can't believe this engine still runs!

I'm guessing there is a block-off plate for the crankcase drain ... is there any reason to keep it? I'm ok with removing it... but then I'll have that little tab on the exhaust holding nothing. I'll lose sleep... and then I'll have to cut it off, smooth he cut ... and then I'll have to refinish... or maybe polish the whole thing... and then 2025 will be here and I will still be working in my garage, and managing OCD

 

[WFO Speedracer]

Actually you can just flip the stock plate over and reinstall it with case sealer and it's free.

 

[mn_reeds]

Multiple ways to delete them - WFO mentions a free and reversible option. I wanted something more permanent so after cleaning the drain holes really well I coated a pair of 8mm x 12mm bolts with JB/devcon and ran them in. No tap is needed so you don't need to worry about shavings.

 

[kevbo]

It looks like a nice hull. It needs to be completely disassembled, inspected, and upgraded. There are very few people, especially jet skiers, who will spend $3000+ and a lot of time to bring an old 650sx up to like new condition with 50MPH power, that’s also reliable. You do have many good options but there will be a significant learning curve to get any ski to run as well as it can.

 

[WFO Speedracer]

It looks like a nice hull. It needs to be completely disassembled, inspected, and upgraded. There are very few people, especially jet skiers, who will spend $3000+ and a lot of time to bring an old 650sx up to like new condition with 50MPH power, that’s also reliable. You do have many good options but there will be a significant learning curve to get any ski to run as well as it can.

How do you spend $3000 on a 650SX that doesn't need an engine rebuild and all the electronics work ?

 

[RiverBandit]

How do you spend $3000 on a 650SX that doesn't need an engine rebuild and all the electronics work ?

I spent $2000 and this ski looks like I got lucky ... I opened the e-box and it's dry as a bone. I have not checked the stator yet. I think with some parts and elbow grease I'll be in this ski for under $3000.

That said, I really don't care what this project ends up costing me. The first ski I ever rode was a late 1970s Kawasaki JS440 ... I was 10 years old. My best friend got a Kawasaki X2 the first year they were out ... I lived "down the shore" in an area where we had rivers on one side and the ocean on the other. My childhood memories are filled with sunrises on the beach, and endless summer days in the ocean jumping waves.

In 1990 I bought an 80s 550 and named it "Splinter". I stripped the hull, painted it Velocity Yellow, glued some purple mats, and set it up for ocean riding. I rebuilt the top end and installed West Coast everything which was readily available back then. In 1994 my girlfriend bought a Yamaha SuperJet and soon after I bought the 1995 Kawasaki 550sx. My girlfriend was obsessed with IJSBA racing, Chris the Fish, and I had a thing for Christy Carlson ... We spent all our free time racing each other, trading paint round buoys, and pretending we were pro racers. I remember sleeping on the beach and leaving only to buy fuel and food. I was known for getting pulled out of the Atlantic by the State Police on double red flag days, and we learned to ride 2-up on a SuperJet ... Kim would wedge herself at the front of the tray and I would drag myself and get us going. We were the only could I ever encountered that rode 2-up. Time marched on, I got married, and children came ... last memory of skiing I hauled our boats from NJ to Maine - Eagle Lake - for a family vacation.

So... for me, this Jet Ski is an old friend. It's something that's deeply embedded in my DNA and the same as salt water and sand. I think I've reached a point in my life where I can say I've spent more time on the tray of a stand-up ski than most of you hear, and that learning curve, I experienced from 1980 through 1990. I do not care what this project costs. I only care that I am able to still remember the sounds, smells, and sensations of riding a jet ski so vividly that it feels like yesterday. I'm not as fast, or agile, but I can still stand.

 

[Sparkplug]

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.

 

[kevbo]

How do you spend $3000 on a 650SX that doesn't need an engine rebuild and all the electronics work ?

After seeing those reeds??

 

[WFO Speedracer]

Reeds and compression are two different things, either it has compression or it doesn't, but yeah if it were mine I might take a look inside to see how everything looks.

 

[Sparkplug]

I got a pair of ts 650 on a trailer before. From some crackhead. I think I paid 150 bucks for both. Got em home. And one was completely full of red brown water. Like hydro locked. We pulled the plugs. Pumped it out. Got it running. And beat the ever living crap out of it at shasta for an entire weekend. Sensi Sci beached it like 150 ft up into camp. Then it got sold to a buddy, and he beat the poop out of it for 2 years until the pump got destroyed and no one wanted to deal with it. Engine still runs fine.

Could it blow? Sure. I feel like if they are gonna. They are gonna regardless.

 

[WFO Speedracer]

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.