Super Jet air leak locations on SJ 701 engine?

[adamrs80]

Last time I went riding my SJ went into a free-revving condition where I could not shut it off. I'm guess that I have an air leak. My crank seals are new so those are ruled out. What are some other possible locations for leaks that could cause a lean condition at idle?

 

[tor*p*do]

intake manifold, case bond line, base gasket.
pressurize motor like a leak test at 8 psi
spray with a mixture of dish detergent out of a windex bottle and look for bubbles

 

[Waternut]

You can have an air leak anywhere to be totally honest. I'm betting you were low on gas and it was out of the water. If so, that's most likely your problem unless the ski has been acting funny lately.

 

[adamrs80]

intake manifold, case bond line, base gasket.
pressurize motor like a leak test at 8 psi
spray with a mixture of dish detergent out of a windex bottle and look for bubbles

Do you know of a link to build a leakdown test setup? I thought I had seen one a while back.

 

[adamrs80]

You can have an air leak anywhere to be totally honest. I'm betting you were low on gas and it was out of the water. If so, that's most likely your problem unless the ski has been acting funny lately.

That would make the most sense because I was thinking all weekend about how well the ski was running. No issues at all. It's just a 701 single 44sbn with an R&D rec. head, MSD enhancer, and a limited B-pipe. I'm running one size larger main jet (147.5 rather than 145) than factory recommended and I know I'm not lean on the low end. I tend to run the carb on the slightly rich side just to be safe.

 

[Waternut]

If you decide you want to pressure test the engine, here is a write up I did a while back. http://www.pwctoday.com/f64/how-pressure-test-your-engine-166854.html

I'm betting if you filled the ski back up with gas and let it idle a few seconds before blipping the throttle, it will be normal again. If you have a run away engine (free revving/stop button doesn't work) again, pull the throttle. It exactly opposite of what you think but the extra fuel will cool the spark plugs and stop it.

 

[adamrs80]

I have heard to pull the throttle before but I never think to do it in the moment. Don't you have to pull the plug wires first to stop the spark before you pull the throttle wide open? It makes sense that the fuel would cool the plugs but if they're still sparking I can see it over-revving. Thanks for the leak down link

 

[Waternut]

The principle behind a run away engine is too little fuel and too much air. The engine gets real lean and the plugs get red hot and they ignite the fuel without a spark. This is why pulling the lanyard and pulling spark plug wires does nothing. Once the plugs cool down from a little extra fuel, they can no longer ignite the remaining fuel.