New owner 94 spx

[One1]

Picked this up today for the kids. I've owned a yamaha 650 2 stroke, but only had it 6 months so my jet ski experience is limited. I build motorcycle engines and atvs so I'm capable, but haven't ever had my fingers in the cookie jar. It runs good as best I can tell but i only got it today. I'm looking to do testing before i turn them loose to make sure pumps and mixing, etc is all working. I'd love some advice on pre-ride tests.

Not to be confused with buying a ski tests. I'm talking last minute checklist on hoses, etc. I have a compression tester and will check for at least 150 psi. The rest of the ski I'm unsure about what to look for. I do know that i need to seal the electrical box. I have read about those connections. I had to wash a LOT of 2 stroke oil out of the hull so I'll need to find out why.

 

[mikidymac]

First off that is going to be a great ski for the kids.
A few things you should know about Seadoo's.......
First from the staining I can see it has the wrong oil because it is blue in the tank. Seadoo's absolutely have to use API-TC oil, no blue TCW-3 like a Yamaha. You will need to drain the oil tank, change the oil filter flush the block because oil lubes the rotary valve and install the correct API-TC oil. Now would be the time to repalce the small 3/32" oil lines from the pump to the intake manifold because they get old, break and toast the engine.

Fuel system has to be spotless, if it has gray fuel lines replace them, rebuild the carb with Genuine Mikuni parts ONLY! replace the fuel valve and filter o-ring.

Change the jet pump oil and inspect the wear-ring and impeller. Other than that you should have a fun reliable ski for many more summers.

 

[One1]

Good start. Thanks a bunch. Most 2 strokes I've had sip 2 stroke at a reasonable pace. How many hours would i run before i get low on this oil?

 

[mikidymac]

On that engine you should be able to get at least 5 or more tanks of gas to one oil.

 

[One1]

Awesome. Thanks. I need to figure out why it puddled 2 stroke behind it after dry running 10 seconds. It was stood up to wash out yesterday if that makes a difference in it filling the exhaust. I need to get a manual for this thing. I'm guessing that the two stroke is on a vacuum operated petcock and maybe it's valve is not closing?

 

[mikidymac]

It could be leaking crank seals from sitting a long time especially with the wrong TCW-3 oil in it. From how black and nasty it is though in my experience it is from a leaking needle and seat flooding the engine.

Has it been sitting long before you got it
?
If it was mine I would check compression, if it's good move forward. From there if it is good I would fully rebuild the fuel system and get the correct oil in it and see if the seals are in fact bad.

 

[One1]

I don't have a history on it, but we had a harsh winter and extended into april so it's been put up 8 months at least. Compression is 125ish, it's not horrible. I only checked cold closed throttle. I know 150 is perfect but most used skis aren't going to hit that number and will run the season. When I was building yamaha YZ race bikes we would see low numbers and they would still run all season. Long as it doesn't die from low compression when hot they didn't really have any usability issues. That was single piston, i know dual piston needs to be within 10% to keep the crankshaft happy.

Has anyone here noticed if the sleeves wear out quicker than the piston rings on the 657? I'm wondering what my chances are of trying a set of rings first. If i can get the season on the engine I'll rebuild it over the winter.

 

[mwat65]

The cheap way out usually costs you in the long run on Seadoos. At 125 it will struggle to run in the water if it runs at all. If pieces of your rings or pistons start coming apart it will ruin your head and possibly get into your crank. Just my opinion but if put a new topend in now with those numbers. Also double check with another tester to make sure your numbers are right.

 

[mwat65]

Fresh battery. Throttle wide open when testing.