Super Jet Advice on Engine Build

J-Bomber

J-Bomber

Go hard or go home.
Location
Wainfleet, Ontario
So here’s the dealio. Bought this 90 650 superjet for $800 needed a battery. Seller said it had been sitting for a few years, but had owned it for almost 15 years. Took it home and removed the plugs to have a looksie into the cylinders and saw that the top of the pistons was holding some rust (oh dear). Removed the carb and saw water sitting in the manifold. :aargh4:
So long story short..

  • inner crank bearings are sub-par, outer bearings very noisy
  • rear piston had to be heated and smashed out, but surprisingly didn’t crack or show damage
  • cylinders weren’t great but a nice hone job cleaned them up
  • case is in good shape considering
  • rings are seized solid into pistons


So my options are

  1. Order new crank and seals and run original top end (if rings are salvageable) and case with new crank while saving $$ for 701 top end
  2. Run the whole original works until it blows up
  3. Sit on the shore and watch my friends jetskiing


My financial situation is not ideal as I am 17 and headed to University next year. If anyone has any opinions or suggestions I am all ears. I’m still new to jetskis and would love some advice. Thanks
 
naticen

naticen

Site Supporter
Location
wilmington, nc
I'm glad to see it work out for you. I had to take a year off riding in college because I couldn't afford a new top end and it was horrible.

Now go ahead and port out that other motor and throw a pipe on it and be ready to switch internals. You'll be smoking 701's and have half the money invested.
 
J-Bomber

J-Bomber

Go hard or go home.
Location
Wainfleet, Ontario
naticen said:
I'm glad to see it work out for you. I had to take a year off riding in college because I couldn't afford a new top end and it was horrible.

Now go ahead and port out that other motor and throw a pipe on it and be ready to switch internals. You'll be smoking 701's and have half the money invested.
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A year off from riding? Sounds like a nightmare.

Quick question off of that, what is the measurement in thousandths to get to 701?
 
yurkanip

yurkanip

Location
Great Pacific Northwest
mthomps said:
A functioning 6m6 motor and a good prop is a great time.
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Agreed, before I dropped my 718 in my square my 650 was soo much fun with nothing more than a 9/15 hooker. Impros assured me that the motor would turn it just fine and they were spot on. Go with that prop and when you are able to upgrade Motor the prop will be in the sweet spot for a 701+
 
naticen

naticen

Site Supporter
Location
wilmington, nc
Definitely. I forgot to say about the prop. All my girl's square has is a prop and it gets going pretty well. On a tight buoy course, her ski will be right there with the best of them. As far as the boring to a 701, I've never ridden a bored out 650 but assume it would add some power. I just meant enlarge the ports with a dremel. Mainly the exhaust. That will give it the real kick. You can even buy a ported cylinder for $100 a lot of times. For under $600, you'll have all the ski that 90% of riders can handle.
 
J-Bomber

J-Bomber

Go hard or go home.
Location
Wainfleet, Ontario
Sorry for the late reply..
Got the engine on Wednesday and slapped the exhaust on it and dropped it in. Got everything hooked up and had it running on rost off (basically WD40) to get the fuel cycle going. Ran well but had some issues with the fuel movement.
I was cleaning the carb and mixing and matching parts with other carbs that I had when all of a sudden I wasn't getting any spark. :doh:
Tried different plugs, and played with the lanyard and nothing was working, so the ebox was split. Got out the ohm-metre and everything was checking out fine from the stator. Took off flywheel cover to make sure. Bypassed start/stop, still nothing, tried a new coil, aaaand nothing. So really all that's left is the cdi crapping out on me, which isn't all that surprising seeing as I poured water out of the ebox when I first got it, but still not ideal for the long weekend. :no:
But big shout out to Redwood for his help in guiding this noob to what will hopefully be the solution, and for letting me ride his sweet fixed-steer fx1 to cure my broken down blues. :notworthy:
 
mthomps

mthomps

Location
Cleveland
J-Bomber said:
Sorry for the late reply..
Got the engine on Wednesday and slapped the exhaust on it and dropped it in. Got everything hooked up and had it running on rost off (basically WD40) to get the fuel cycle going. Ran well but had some issues with the fuel movement.
I was cleaning the carb and mixing and matching parts with other carbs that I had when all of a sudden I wasn't getting any spark. :doh:
Tried different plugs, and played with the lanyard and nothing was working, so the ebox was split. Got out the ohm-metre and everything was checking out fine from the stator. Took off flywheel cover to make sure. Bypassed start/stop, still nothing, tried a new coil, aaaand nothing. So really all that's left is the cdi crapping out on me, which isn't all that surprising seeing as I poured water out of the ebox when I first got it, but still not ideal for the long weekend. :no:
But big shout out to Redwood for his help in guiding this noob to what will hopefully be the solution, and for letting me ride his sweet fixed-steer fx1 to cure my broken down blues. :notworthy:
Click to expand...

Hope its your cdi and a quick fix so you can ride soon
 
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