SJ - won’t rev up in water

[Sferone]

I just did a rebuild after 10 years on my sn superjet. It’s got the usual set up of Factory Pipe, ADA head, MSD enhancer etc. I’m running dual 46 mm Mikunis.
I broke it in for an hour last weekend then switched out the plugs and ran a tank through it. It ran perfect. I got a solid 3 hours of great riding out of it

Today was a different story. It revved up fine on the trailer but when I put in the water, it would not rev up. It would idle on the water but would not go over about 3000 RPMs when I gave it full throttle. I checked the plugs and the front cylinder is running rich. I swapped out plugs and it did the same thing. The coil is a new rebuilt one so I swapped the plug wires and it still did the same thing.

I tried to search the subject but I’m not coming up with anything so any help would be greatly appreciated

Thanks

Steve

 

[mthomps]

I have no idea so here is a bump. Someone help this guy.

Things I'd try: blow test your 1 way valve on the tank, check all fuel lines for leaks. Swap cdi's if u or a friend have a spare. Ride the ski around with the hood off.

Good luck. Your ski is too clean. I hope it gets wet and dirty soon

 

[JetManiac]

Did you check the carb linkage to see if slipped/stripped and carb butterflies out of alignment?

 

[DAG]

Where in NC are you located?

Being that it ran fine for a full tank after the rebuild makes me think something got loose. Running without the hood (even strapped to the trailer while in the water) will show if a water line is leaking or exhaust gasses are leaking under the hood.

Did you rebuild the carbs?

It sounds like something little was missed. Maybe sucked up a rope/stick/rock and pump is cavitating? look for the little things before going to crazy

 

[jo5hi3]

I once had a cdi go bad and do this to me.

 

[superjetguy]

CDI is bad. Maybe check your fuses in the E-Box. 90% sure it’s the CDI

 

[Sferone]

Thanks for the replies. I have checked all that was suggested except for the MSD cdi. It is 10 years old.

I am up in Raleigh

 

[JetManiac]

N/s in front carb leaking, not closing?

 

[Sferone]

You know how in Vegas they say always bet on black..........well on this forum ALWAYS bet on Jetmaniac! One of carb shafts is stripped. I am messaging him now for parts.

Once again thank you all for your help. I was really lost on this one

 

[superjetguy]

Why would that make it any different on water vs the trailer?

 

[Sferone]

My theory is that there’s no load on the engine when it’s out of the water and the ski can run off of one carburetor. The fuel and the air is all mixed in the case but there’s just not enough of it to power it in the water when it’s under load.

 

[2002zxi]

Exact same symptoms on a 93 squarenose I just bought. It was Infuriating to troubleshoot. Was a single broken reed petal.

 

[Vortex]

The one time I had a broken Reed, the thing would not even want to start at all unless you covered the carb(s) with your palm