Super Jet Died during WOT run, rough restarts.

[evowake]

'12 SJ, 35cc domes, B-Pipe, Home-Port, carbon reeds.

So the last few min on the lake before trailering the ski, I did a WOT blast for roughly 1/2 mile down the lake.

Ski abruptly sputtered and died while at WOT. was able to restart, but initially wouldn't stay running. was able to start and baby the throttle for a couple min, then got on plane and cruised back to ramp.

Ski now is hard to start or keep running without giving it a touch of throttle whereas before it would fire right up.

First instinct when I get home today is check compression - suspect i may have blown a dome seal or a ring.

Figured I'd pick the brains here and see if this rings any bells for anyone.

Appreciate it!

 

[Jakobi86]

What you describe sounds like a blown top end through and through


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[Vumad]

You figured right. You probably seized a piston, probablt from being lean.

 

[evowake]

Appreciate the thoughts guys, suppose the teardown begins today.

Thought I added enough up top - suppose not.

This may be a silly question, but is it generally better to start rich and work down versus what I did and slowly open it up?

 

[speedysprocket]

Uh yes, always start rich! Join the lean seizure club in the General section. That makes at least three in like three weeks posted here...

 

[waukie]

Can't safely use 35cc domes on most newer superjets, 08+
Have seen case deck height variances that are different than old #'s.
And p/c clearances come from factory @.002"(not all but)
Stock they live
Anything more rpm,compression (heat) problems begin
Hope its something else but this may be helpful knowledge

 

[Vumad]

I have an 04 superjet bored 1mm over from rebuild. 35cc domes gave me 210psi. I had to go to 37cc domes and got 170psi. I also couldnt go with the suggested 135 main jets nor the 40psi popoff. Im at 140/75@32psi.

Edit: Corrected popoff from 18 to 32. I have 1.5n&s w/ 65g spring. Jets were correct.

 

[augustaf]

#6 post is scary!

 

[JT_Freeride]

I have an 04 superjet bored 1mm over from rebuild. 35cc domes gave me 210psi. I had to go to 37cc domes and got 170psi. I also couldnt go with the suggested 135 main jets nor the 40psi popoff. Im at 140/75@18psi.

Did you break the engine in with those domes. I've seen brand new rebuild with 210-220 psi drop down to 190ish after the break in. Also if you replaced the base gasket that can change numbers as well.

 

[Vumad]

Did you break the engine in with those domes. I've seen brand new rebuild with 210-220 psi drop down to 190ish after the break in. Also if you replaced the base gasket that can change numbers as well.

I put 8 hours on it in daytona that year alone, so im sure at least 10. I didnt feel good about the work so i brought i found someone else to redo some thingz. Not sure on the bzse gasket. It has worked great ever since. Still 170psi.

 

[Big Kahuna]

1/2 mile WOT? No Brainer. You smoked it............ Only ski I could do that on was my Stock Class SXR....... But it was jetted perfectly and I had plenty of cooling........ But still I constantly fluctuated the throttle.

 

[Quinc]

1/2 mile WOT? No Brainer. You smoked it............ Only ski I could do that on was my Stock Class SXR....... But it was jetted perfectly and I had plenty of cooling........ But still I constantly fluctuated the throttle.

I run my freestyle skis WOT all time with no issue. But did a lot of tuning, checking and rechecking things, before I got to that point. Also run a little 100LL as insurance.

 

[Big Kahuna]

I do to. But not 1/2 mile pinned......

 

[evowake]

Good info guys, thank you

I checked the compression when I first set it up, and was seeing 185-190 PSI with the 35's freshly built. ran it all last year (unported) probably 30 hours with no issue. only change this year was new base gasket and ported the exhaust.

figured the long WOT pull was dumb, guess some of the rum from the beachclub was still doing the thinking.

Eh, learning experience, I'll keep you guys posted once I tear it open.

On the plus side, committed 110% to a few barrel roll attempts off of wakeboard boat wakes, made it a bit over half way around on my last try, so I'd consider it a success regardless

 

[augustaf]

careful with that halfway around stuff, might bust a eardrum.

 

[evowake]

Thanks! Was sporting a helmet for those - I've read that a number of times here

careful with that halfway around stuff, might bust a eardrum.

 

[evowake]

Here's the damage guys -

Suppose I need to decide whether to rebuild it as a 701 or go 760

 

[Roseand]

Are there score marks that catch your fingernail in the sleeve? Or is it just aluminum build up?

 

[evowake]

Are there score marks that catch your fingernail in the sleeve? Or is it just aluminum build up?

Didn't notice anything deep, but haven't done a thorough inspection just yet. Saw the Piston and decided to call it a night, and do some research on part costs.

 

[Roseand]

Yeah check for deep marks. You might have gotten lucky. I did with my cylinder. Was full of aluminum deposits but zero scoring. If you can't notice any deep scores, clean off the aluminum with muriatic acid and go from there.