Could My 701 SJ Flywheel Have Slipped and Advanced the Timing?

[Edmund Fitzjetski]

Hi guys. I had an experience yesterday that has left me completely baffled.

My ski configuration is:

2010 718cc SuperJet
JetManiac ported cylinder
Mod B-Pipe
2cc removed from head (38.5cc w/ gasket)

The ski has been excellent and has run really strong with 100% reliability for 2 years. I let someone ride it yesterday for about 30 seconds. In that time, one of the B-Pipe flange clamps broke and the pipe popped off. We were able to fix it on the fly using both of the zip ties that hold the tool kit on the hood. This was enough to ride it slowly back to the dock for the permanent fix with a new clamp.

Here's the puzzle: The ski rips now! Faster than ever, super crisp response, pulls really hard. WTF? In the 30 seconds of riding, the guy was jumping it in flat water a few times in a row without letting off the throttle. While I don't do this, the ski does still have the stock rev limiter so I'm hoping this was okay. The only theory I have is that the airborne WOTs at low speed could have jarred the flywheel on landing, casuing it to slip (shearing the key) and advancing the timing. While the ski rips now, I don't have confidence that it will last as I don't know what caused it.

Has anyone had the flywheel slip from low speed jumping?

Any thoughts are welcome.

Thank you!

 

[Sparkplug]

You have most likely had an small exhaust leak for a long time and just now got it fixed.

I used to log roll my 650 superjets pinned bouncing off the limiter, and the pump would violently hook up when it rolled over. Bouncing it off the stock limiter a few times out of the water isn't gonna hurt it at all.

 

[Edmund Fitzjetski]

Thank you Sparkplug! I also confirmed that the flywheel slipping isn't a "thing" with the SJs. I suspect that my issue was a restricted water squirter in the B pipe. I was running the middle screw only at about a 1/2 turn. I took the screw out and cleaned it and it now runs the way it did before. I also saw evidence of overheating from the temp label sticker getting wrinkled. So, that's my theory anyway.

Meanwhile, this lead to collecting objective temperature data on the surface of the pipe. The "water should lightly sizzle" thing seemed like more could be offered here. I did a full study with a thermocouple and data acquisition. I'll finish my chart and do a seperate post in case it is helpful for others.

Thanks again!